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.idea
*.iml
*.swp
datanucleus.log
/bin/
/bin/
/bin/
data-mapper/src/main/resources/log4j.xml

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language: java
jdk:
- oraclejdk8
- oraclejdk8
# whitelist
branches:
only:
- master
env:
global:
- GH_REF: github.com/iluwatar/java-design-patterns.git
- secure: LxTDuNS/rBWIvKkaEqr79ImZAe48mCdoYCF41coxNXgNoippo4GIBArknqtv+XvdkiuRZ1yGyj6pn8GU33c/yn+krddTUkVCwTbVatbalW5jhQjDbHYym/JcxaK9ZS/3JTeGcWrBgiPqHEEDhCf26vPZsXoMSeVCEORVKTp1BSg=
before_install:
- export DISPLAY=:99.0
- sh -e /etc/init.d/xvfb start
after_success:
- mvn clean test jacoco:report coveralls:report
- mvn clean test jacoco:report coveralls:report
- bash update-ghpages.sh
sudo: false # route the build to the container-based infrastructure for a faster build

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# Code Coverage Report generation
To generate the code coverage report, execute the following command:
> mvn clean verify
This will generate code coverage report in each of the modules. In order to view the same, open the following file in your browser.
> target/site/jacoco/index.html
Please note that the above folder is created under each of the modules. For example:
* adapter/target/site/jacoco/index.html
* busniess-delegate/target/site/jacoco/index.html

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This is great you have something to contribute!
Before going any further please read the [wiki](https://github.com/iluwatar/java-design-patterns/wiki)
with conventions and rules we used for this project.

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The MIT License (MIT)
Copyright (c) 2014 Ilkka Seppälä
Copyright (c) 2014-2016 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal

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# Design pattern samples in Java.
<!-- the line below needs to be an empty line C: (its because kramdown isnt
that smart and dearly wants an empty line before a heading to be able to
display it as such, e.g. website) -->
## Build status, coverage and static analysis:
# Design patterns implemented in Java
![Build status](https://travis-ci.org/iluwatar/java-design-patterns.svg?branch=master) [![Coverage Status](https://coveralls.io/repos/iluwatar/java-design-patterns/badge.svg?branch=master)](https://coveralls.io/r/iluwatar/java-design-patterns?branch=master) <a href="https://scan.coverity.com/projects/5634">
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## Introduction
# Introduction
Design patterns are formalized best practices that the programmer can use to solve common problems when designing an application or system.
Design patterns are formalized best practices that the programmer can use to
solve common problems when designing an application or system.
Design patterns can speed up the development process by providing tested, proven development paradigms.
Design patterns can speed up the development process by providing tested, proven
development paradigms.
Reusing design patterns helps to prevent subtle issues that can cause major problems, and it also improves code readability for coders and architects who are familiar with the patterns.
Reusing design patterns helps to prevent subtle issues that can cause major
problems, and it also improves code readability for coders and architects who
are familiar with the patterns.
## <a name="list-of-design-patterns">List of Design Patterns</a>
# Getting started
### Creational Patterns
Before you dive into the material, you should be familiar with various
[Programming/Software Design Principles](http://webpro.github.io/programming-principles/).
Creational design patterns abstract the instantiation process. They help make a system independent of how its objects are created, composed, and represented.
* [Abstract Factory](#abstract-factory)
* [Builder](#builder)
* [Factory Method](#factory-method)
* [Prototype](#prototype)
* [Property](#property)
* [Singleton](#singleton)
* [Multiton](#multiton)
* [Object Pool](#object-pool)
### Structural Patterns
Structural patterns are concerned with how classes and objects are composed to form larger structures.
* [Adapter](#adapter)
* [Bridge](#bridge)
* [Composite](#composite)
* [Decorator](#decorator)
* [Facade](#facade)
* [Flyweight](#flyweight)
* [Proxy](#proxy)
* [Service Locator](#service-locator)
* [Servant](#servant)
* [Event Aggregator](#event-aggregator)
### Behavioral Patterns
Behavioral patterns are concerned with algorithms and the assignment of responsibilites between objects.
* [Chain of responsibility](#chain-of-responsibility)
* [Command](#command)
* [Interpreter](#interpreter)
* [Iterator](#iterator)
* [Mediator](#mediator)
* [Memento](#memento)
* [Observer](#observer)
* [State](#state)
* [Strategy](#strategy)
* [Template method](#template-method)
* [Visitor](#visitor)
* [Null Object](#null-object)
* [Intercepting Filter](#intercepting-filter)
* [Specification](#specification)
* [Dependency Injection](#dependency-injection)
### Concurrency Patterns
Concurrency patterns are those types of design patterns that deal with the multi-threaded programming paradigm.
* [Double Checked Locking](#double-checked-locking)
* [Thread Pool](#thread-pool)
### Presentation Tier Patterns
Presentation Tier patterns are the top-most level of the application, this is concerned with translating tasks and results to something the user can understand.
* [Model-View-Controller](#model-view-controller)
* [Model-View-Presenter](#model-view-presenter)
* [Flux](#flux)
### Architectural Patterns
An architectural pattern is a general, reusable solution to a commonly occurring problem in software architecture within a given context.
* [Data Access Object](#dao)
* [Service Layer](#service-layer)
### Integration Patterns
Integration patterns are concerned with how software applications communicate and exchange data.
* [Tolerant Reader](#tolerant-reader)
### Idioms
A programming idiom is a means of expressing a recurring construct in one or more programming languages. Generally speaking, a programming idiom is an expression of a simple task, algorithm, or data structure that is not a built-in feature in the programming language being used, or, conversely, the use of an unusual or notable feature that is built into a programming language. What distinguishes idioms from patterns is generally the size, the idioms tend to be something small while the patterns are larger.
* [Execute Around](#execute-around)
* [Poison Pill](#poison-pill)
* [Callback](#callback)
* [Lazy Loading](#lazy-loading)
* [Double Dispatch](#double-dispatch)
* [Resource Acquisition Is Initialization](#resource-acquisition-is-initialization)
* [Private Class Data](#private-class-data)
## <a name="abstract-factory">Abstract Factory</a> [&#8593;](#list-of-design-patterns)
**Intent:** Provide an interface for creating families of related or dependent objects without specifying their concrete classes.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/abstract-factory/etc/abstract-factory_1.png "Abstract Factory")
**Applicability:** Use the Abstract Factory pattern when
* a system should be independent of how its products are created, composed and represented
* a system should be configured with one of multiple families of products
* a family of related product objects is designed to be used together, and you need to enforce this constraint
* you want to provide a class library of products, and you want to reveal just their interfaces, not their implementations
**Real world examples:**
* [javax.xml.parsers.DocumentBuilderFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/parsers/DocumentBuilderFactory.html)
## <a name="builder">Builder</a> [&#8593;](#list-of-design-patterns)
**Intent:** Separate the construction of a complex object from its representation so that the same construction process can create different representations.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/builder/etc/builder_1.png "Builder")
**Applicability:** Use the Builder pattern when
* the algorithm for creating a complex object should be independent of the parts that make up the object and how they're assembled
* the construction process must allow different representations for the object that's constructed
**Real world examples:**
* [java.lang.StringBuilder](http://docs.oracle.com/javase/8/docs/api/java/lang/StringBuilder.html)
* [Apache Camel builders](https://github.com/apache/camel/tree/0e195428ee04531be27a0b659005e3aa8d159d23/camel-core/src/main/java/org/apache/camel/builder)
## <a name="factory-method">Factory Method</a> [&#8593;](#list-of-design-patterns)
**Intent:** Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/factory-method/etc/factory-method_1.png "Factory Method")
**Applicability:** Use the Factory Method pattern when
* a class can't anticipate the class of objects it must create
* a class wants its subclasses to specify the objects it creates
* classes delegate responsibility to one of several helper subclasses, and you want to localize the knowledge of which helper subclass is the delegate
## <a name="prototype">Prototype</a> [&#8593;](#list-of-design-patterns)
**Intent:** Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/prototype/etc/prototype_1.png "Prototype")
**Applicability:** Use the Prototype pattern when a system should be independent of how its products are created, composed and represented; and
* when the classes to instantiate are specified at run-time, for example, by dynamic loading; or
* to avoid building a class hierarchy of factories that parallels the class hierarchy of products; or
* when instances of a class can have one of only a few different combinations of state. It may be more convenient to install a corresponding number of prototypes and clone them rather than instantiating the class manually, each time with the appropriate state
**Real world examples:**
* [java.lang.Object#clone()](http://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#clone%28%29)
## <a name="singleton">Singleton</a> [&#8593;](#list-of-design-patterns)
**Intent:** Ensure a class only has one instance, and provide a global point of access to it.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/singleton/etc/singleton_1.png "Singleton")
**Applicability:** Use the Singleton pattern when
* there must be exactly one instance of a class, and it must be accessible to clients from a well-known access point
* when the sole instance should be extensible by subclassing, and clients should be able to use an extended instance without modifying their code
**Typical Use Case:**
* the logging class
* managing a connection to a database
* file manager
**Real world examples:**
* [java.lang.Runtime#getRuntime()](http://docs.oracle.com/javase/8/docs/api/java/lang/Runtime.html#getRuntime%28%29)
## <a name="adapter">Adapter</a> [&#8593;](#list-of-design-patterns)
**Intent:** Convert the interface of a class into another interface the clients expect. Adapter lets classes work together that couldn't otherwise because of incompatible interfaces.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/adapter/etc/adapter_1.png "Adapter")
**Applicability:** Use the Adapter pattern when
* you want to use an existing class, and its interface does not match the one you need
* you want to create a reusable class that cooperates with unrelated or unforeseen classes, that is, classes that don't necessarily have compatible interfaces
* you need to use several existing subclasses, but it's impractical to adapt their interface by subclassing every one. An object adapter can adapt the interface of its parent class.
**Real world examples:**
* [java.util.Arrays#asList()](http://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#asList%28T...%29)
## <a name="bridge">Bridge</a> [&#8593;](#list-of-design-patterns)
**Intent:** Decouple an abstraction from its implementation so that the two can vary independently.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/bridge/etc/bridge_1.png "Bridge")
**Applicability:** Use the Bridge pattern when
* you want to avoid a permanent binding between an abstraction and its implementation. This might be the case, for example, when the implementation must be selected or switched at run-time.
* both the abstractions and their implementations should be extensible by subclassing. In this case, the Bridge pattern lets you combine the different abstractions and implementations and extend them independently
* changes in the implementation of an abstraction should have no impact on clients; that is, their code should not have to be recompiled.
* you have a proliferation of classes. Such a class hierarchy indicates the need for splitting an object into two parts. Rumbaugh uses the term "nested generalizations" to refer to such class hierarchies
* you want to share an implementation among multiple objects (perhaps using reference counting), and this fact should be hidden from the client. A simple example is Coplien's String class, in which multiple objects can share the same string representation.
## <a name="composite">Composite</a> [&#8593;](#list-of-design-patterns)
**Intent:** Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/composite/etc/composite_1.png "Composite")
**Applicability:** Use the Composite pattern when
* you want to represent part-whole hierarchies of objects
* you want clients to be able to ignore the difference between compositions of objects and individual objects. Clients will treat all objects in the composite structure uniformly
**Real world examples:**
* [java.awt.Container](http://docs.oracle.com/javase/8/docs/api/java/awt/Container.html) and [java.awt.Component](http://docs.oracle.com/javase/8/docs/api/java/awt/Component.html)
* [Apache Wicket](https://github.com/apache/wicket) component tree, see [Component](https://github.com/apache/wicket/blob/91e154702ab1ff3481ef6cbb04c6044814b7e130/wicket-core/src/main/java/org/apache/wicket/Component.java) and [MarkupContainer](https://github.com/apache/wicket/blob/b60ec64d0b50a611a9549809c9ab216f0ffa3ae3/wicket-core/src/main/java/org/apache/wicket/MarkupContainer.java)
## <a name="decorator">Decorator</a> [&#8593;](#list-of-design-patterns)
**Intent:** Attach additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/decorator/etc/decorator_1.png "Decorator")
**Applicability:** Use Decorator
* to add responsibilities to individual objects dynamically and transparently, that is, without affecting other objects
* for responsibilities that can be withdrawn
* when extension by subclassing is impractical. Sometimes a large number of independent extensions are possible and would produce an explosion of sublasses to support every combination. Or a class definition may be hidden or otherwise unavailable for subclassing
## <a name="facade">Facade</a> [&#8593;](#list-of-design-patterns)
**Intent:** Provide a unified interface to a set of interfaces in a subsystem. Facade defines a higher-level interface that makes the subsystem easier to use.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/facade/etc/facade_1.png "Facade")
**Applicability:** Use the Facade pattern when
* you want to provide a simple interface to a complex subsystem. Subsystems often get more complex as they evolve. Most patterns, when applied, result in more and smaller classes. This makes the subsystem more reusable and easier to customize, but it also becomes harder to use for clients that don't need to customize it. A facade can provide a simple default view of the subsystem that is good enough for most clients. Only clients needing more customizability will need to look beyond the facade.
* there are many dependencies between clients and the implementation classes of an abstraction. Introduce a facade to decouple the subsystem from clients and other subsystems, thereby promoting subsystem independence and portability.
* you want to layer your subsystems. Use a facade to define an entry point to each subsystem level. If subsystems are dependent, the you can simplify the dependencies between them by making them communicate with each other solely through their facades
## <a name="flyweight">Flyweight</a> [&#8593;](#list-of-design-patterns)
**Intent:** Use sharing to support large numbers of fine-grained objects efficiently.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/flyweight/etc/flyweight_1.png "Flyweight")
**Applicability:** The Flyweight pattern's effectiveness depends heavily on how and where it's used. Apply the Flyweight pattern when all of the following are true
* an application uses a large number of objects
* storage costs are high because of the sheer quantity of objects
* most object state can be made extrinsic
* many groups of objects may be replaced by relatively few shared objects once extrinsic state is removed
* the application doesn't depend on object identity. Since flyweight objects may be shared, identity tests will return true for conceptually distinct objects.
**Real world examples:**
* [java.lang.Integer#valueOf(int)](http://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html#valueOf%28int%29)
## <a name="proxy">Proxy</a> [&#8593;](#list-of-design-patterns)
**Intent:** Provide a surrogate or placeholder for another object to control access to it.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/proxy/etc/proxy_1.png "Proxy")
**Applicability:** Proxy is applicable whenever there is a need for a more versatile or sophisticated reference to an object than a simple pointer. Here are several common situations in which the Proxy pattern is applicable
* a remote proxy provides a local representative for an object in a different address space.
* a virtual proxy creates expensive objects on demand.
* a protection proxy controls access to the original object. Protection proxies are useful when objects should have different access rights.
**Typical Use Case:**
* Control access to another object
* Lazy initialization
* implement logging
* facilitate network connection
* to count references to an object
**Real world examples:**
* [java.lang.reflect.Proxy](http://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Proxy.html)
* [Apache Commons Proxy](https://commons.apache.org/proper/commons-proxy/)
## <a name="service-locator">Service Locator</a> [&#8593;](#list-of-design-patterns)
**Intent:** Encapsulate the processes involved in obtaining a service with a strong abstraction layer.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/service-locator/etc/service-locator.png "Proxy")
**Applicability:** The service locator pattern is applicable whenever we want to locate/fetch various services using JNDI which, typically, is a redundant and expensive lookup. The service Locator pattern addresses this expensive lookup by making use of caching techniques ie. for the very first time a particular service is requested, the service Locator looks up in JNDI, fetched the relavant service and then finally caches this service object. Now, further lookups of the same service via Service Locator is done in its cache which improves the performance of application to great extent.
**Typical Use Case:**
* When network hits are expensive and time consuming
* lookups of services are done quite frequently
* large number of services are being used
## <a name="chain-of-responsibility">Chain of responsibility</a> [&#8593;](#list-of-design-patterns)
**Intent:** Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/chain/etc/chain_1.png "Chain of Responsibility")
**Applicability:** Use Chain of Responsibility when
* more than one object may handle a request, and the handler isn't known a priori. The handler should be ascertained automatically
* you want to issue a request to one of several objects without specifying the receiver explicitly
* the set of objects that can handle a request should be specified dynamically
**Real world examples:**
* [java.util.logging.Logger#log()](http://docs.oracle.com/javase/8/docs/api/java/util/logging/Logger.html#log%28java.util.logging.Level,%20java.lang.String%29)
* [Apache Commons Chain](https://commons.apache.org/proper/commons-chain/index.html)
## <a name="command">Command</a> [&#8593;](#list-of-design-patterns)
**Intent:** Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/command/etc/command.png "Command")
**Applicability:** Use the Command pattern when you want to
* parameterize objects by an action to perform. You can express such parameterization in a procedural language with a callback function, that is, a function that's registered somewhere to be called at a later point. Commands are an object-oriented replacement for callbacks.
* specify, queue, and execute requests at different times. A Command object can have a lifetime independent of the original request. If the receiver of a request can be represented in an address space-independent way, then you can transfer a command object for the request to a different process and fulfill the request there
* support undo. The Command's execute operation can store state for reversing its effects in the command itself. The Command interface must have an added Unexecute operation that reverses the effects of a previous call to execute. Executed commands are stored in a history list. Unlimited-level undo and redo is achieved by traversing this list backwards and forwards calling unexecute and execute, respectively
* support logging changes so that they can be reapplied in case of a system crash. By augmenting the Command interface with load and store operations, you can keep a persistent log of changes. Recovering from a crash involves reloading logged commands from disk and re-executing them with the execute operation
* structure a system around high-level operations build on primitive operations. Such a structure is common in information systems that support transactions. A transaction encapsulates a set of changes to data. The Command pattern offers a way to model transactions. Commands have a common interface, letting you invoke all transactions the same way. The pattern also makes it easy to extend the system with new transactions
**Typical Use Case:**
* to keep a history of requests
* implement callback functionality
* implement the undo functionality
**Real world examples:**
* [java.lang.Runnable](http://docs.oracle.com/javase/8/docs/api/java/lang/Runnable.html)
## <a name="interpreter">Interpreter</a> [&#8593;](#list-of-design-patterns)
**Intent:** Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/interpreter/etc/interpreter_1.png "Interpreter")
**Applicability:** Use the Interpreter pattern when there is a language to interpret, and you can represent statements in the language as abstract syntax trees. The Interpreter pattern works best when
* the grammar is simple. For complex grammars, the class hierarchy for the grammar becomes large and unmanageable. Tools such as parser generators are a better alternative in such cases. They can interpret expressions without building abstract syntax trees, which can save space and possibly time
* efficiency is not a critical concern. The most efficient interpreters are usually not implemented by interpreting parse trees directly but by first translating them into another form. For example, regular expressions are often transformed into state machines. But even then, the translator can be implemented by the Interpreter pattern, so the pattern is still applicable
## <a name="iterator">Iterator</a> [&#8593;](#list-of-design-patterns)
**Intent:** Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/iterator/etc/iterator_1.png "Iterator")
**Applicability:** Use the Iterator pattern
* to access an aggregate object's contents without exposing its internal representation
* to support multiple traversals of aggregate objects
* to provide a uniform interface for traversing different aggregate structures
**Real world examples:**
* [java.util.Iterator](http://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html)
## <a name="mediator">Mediator</a> [&#8593;](#list-of-design-patterns)
**Intent:** Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/mediator/etc/mediator_1.png "Mediator")
**Applicability:** Use the Mediator pattern when
* a set of objects communicate in well-defined but complex ways. The resulting interdependencies are unstructured and difficult to understand
* reusing an object is difficult because it refers to and communicates with many other objects
* a behavior that's distributed between several classes should be customizable without a lot of subclassing
## <a name="memento">Memento</a> [&#8593;](#list-of-design-patterns)
**Intent:** Without violating encapsulation, capture and externalize an object's internal state so that the object can be restored to this state later.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/memento/etc/memento.png "Memento")
**Applicability:** Use the Memento pattern when
* a snapshot of an object's state must be saved so that it can be restored to that state later, and
* a direct interface to obtaining the state would expose implementation details and break the object's encapsulation
**Real world examples:**
* [java.util.Date](http://docs.oracle.com/javase/8/docs/api/java/util/Date.html)
## <a name="observer">Observer</a> [&#8593;](#list-of-design-patterns)
**Intent:** Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/observer/etc/observer_1.png "Observer")
**Applicability:** Use the Observer pattern in any of the following situations
* when an abstraction has two aspects, one dependent on the other. Encapsulating these aspects in separate objects lets you vary and reuse them independently
* when a change to one object requires changing others, and you don't know how many objects need to be changed
* when an object should be able to notify other objects without making assumptions about who these objects are. In other words, you don't want these objects tightly coupled
**Typical Use Case:**
* changing in one object leads to a change in other objects
**Real world examples:**
* [java.util.Observer](http://docs.oracle.com/javase/8/docs/api/java/util/Observer.html)
## <a name="state">State</a> [&#8593;](#list-of-design-patterns)
**Intent:** Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/state/etc/state_1.png "State")
**Applicability:** Use the State pattern in either of the following cases
* an object's behavior depends on its state, and it must change its behavior at run-time depending on that state
* operations have large, multipart conditional statements that depend on the object's state. This state is usually represented by one or more enumerated constants. Often, several operations will contain this same conditional structure. The State pattern puts each branch of the conditional in a separate class. This lets you treat the object's state as an object in its own right that can vary independently from other objects.
## <a name="strategy">Strategy</a> [&#8593;](#list-of-design-patterns)
**Intent:** Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/strategy/etc/strategy_1.png "Strategy")
**Applicability:** Use the Strategy pattern when
* many related classes differ only in their behavior. Strategies provide a way to configure a class either one of many behaviors
* you need different variants of an algorithm. for example, you might define algorithms reflecting different space/time trade-offs. Strategies can be used when these variants are implemented as a class hierarchy of algorithms
* an algorithm uses data that clients shouldn't know about. Use the Strategy pattern to avoid exposing complex, algorithm-specific data structures
* a class defines many behaviors, and these appear as multiple conditional statements in its operations. Instead of many conditionals, move related conditional branches into their own Strategy class
## <a name="template-method">Template method</a> [&#8593;](#list-of-design-patterns)
**Intent:** Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Template method lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/template-method/etc/template-method_1.png "Template Method")
**Applicability:** The Template Method pattern should be used
* to implement the invariant parts of an algorithm once and leave it up to subclasses to implement the behavior that can vary
* when common behavior among subclasses should be factored and localized in a common class to avoid code duplication. This is good example of "refactoring to generalize" as described by Opdyke and Johnson. You first identify the differences in the existing code and then separate the differences into new operations. Finally, you replace the differing code with a template method that calls one of these new operations
* to control subclasses extensions. You can define a template method that calls "hook" operations at specific points, thereby permitting extensions only at those points
## <a name="visitor">Visitor</a> [&#8593;](#list-of-design-patterns)
**Intent:** Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/visitor/etc/visitor_1.png "Visitor")
**Applicability:** Use the Visitor pattern when
* an object structure contains many classes of objects with differing interfaces, and you want to perform operations on these objects that depend on their concrete classes
* many distinct and unrelated operations need to be performed on objects in an object structure, and you want to avoid "polluting" their classes with these operations. Visitor lets you keep related operations together by defining them in one class. When the object structure is shared by many applications, use Visitor to put operations in just those applications that need them
* the classes defining the object structure rarely change, but you often want to define new operations over the structure. Changing the object structure classes requires redefining the interface to all visitors, which is potentially costly. If the object structure classes change often, then it's probably better to define the operations in those classes
**Real world examples:**
* [Apache Wicket](https://github.com/apache/wicket) component tree, see [MarkupContainer](https://github.com/apache/wicket/blob/b60ec64d0b50a611a9549809c9ab216f0ffa3ae3/wicket-core/src/main/java/org/apache/wicket/MarkupContainer.java)
## <a name="model-view-presenter">Model-View-Presenter</a> [&#8593;](#list-of-design-patterns)
**Intent:** Apply a "Separation of Concerns" principle in a way that allows developers to build and test user interfaces.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/model-view-presenter/etc/model-view-presenter_1.png "Model-View-Presenter")
**Applicability:** Use the Model-View-Presenter in any of the following situations
* when you want to improve the "Separation of Concerns" principle in presentation logic
* when a user interface development and testing is necessary.
## <a name="dao">Data Access Object</a> [&#8593;](#list-of-design-patterns)
**Intent:** Object provides an abstract interface to some type of database or other persistence mechanism.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/dao/etc/dao.png "Data Access Object")
**Applicability:** Use the Data Access Object in any of the following situations
* when you want to consolidate how the data layer is accessed
* when you want to avoid writing multiple data retrieval/persistence layers
## <a name="double-checked-locking">Double Checked Locking</a> [&#8593;](#list-of-design-patterns)
**Intent:** Reduce the overhead of acquiring a lock by first testing the locking criterion (the "lock hint") without actually acquiring the lock. Only if the locking criterion check indicates that locking is required does the actual locking logic proceed.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/double-checked-locking/etc/double_checked_locking_1.png "Double Checked Locking")
**Applicability:** Use the Double Checked Locking pattern when
* there is a concurrent access in object creation, e.g. singleton, where you want to create single instance of the same class and checking if it's null or not maybe not be enough when there are two or more threads that checks if instance is null or not.
* there is a concurrent access on a method where method's behaviour changes according to the some constraints and these constraint change within this method.
## <a name="servant">Servant</a> [&#8593;](#list-of-design-patterns)
**Intent:** Servant is used for providing some behavior to a group of classes. Instead of defining that behavior in each class - or when we cannot factor out this behavior in the common parent class - it is defined once in the Servant.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/servant/etc/servant-pattern.png "Servant")
**Applicability:** Use the Servant pattern when
* When we want some objects to perform a common action and don't want to define this action as a method in every class.
## <a name="null-object">Null Object</a> [&#8593;](#list-of-design-patterns)
**Intent:** In most object-oriented languages, such as Java or C#, references may be null. These references need to be checked to ensure they are not null before invoking any methods, because methods typically cannot be invoked on null references. Instead of using a null reference to convey absence of an object (for instance, a non-existent customer), one uses an object which implements the expected interface, but whose method body is empty. The advantage of this approach over a working default implementation is that a Null Object is very predictable and has no side effects: it does nothing.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/null-object/etc/null-object.png "Null Object")
**Applicability:** Use the Null Object pattern when
* You want to avoid explicit null checks and keep the algorithm elegant and easy to read.
## <a name="event-aggregator">Event Aggregator</a> [&#8593;](#list-of-design-patterns)
**Intent:** A system with lots of objects can lead to complexities when a client wants to subscribe to events. The client has to find and register for each object individually, if each object has multiple events then each event requires a separate subscription. An Event Aggregator acts as a single source of events for many objects. It registers for all the events of the many objects allowing clients to register with just the aggregator.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/event-aggregator/etc/classes.png "Event Aggregator")
**Applicability:** Use the Event Aggregator pattern when
* Event Aggregator is a good choice when you have lots of objects that are potential event sources. Rather than have the observer deal with registering with them all, you can centralize the registration logic to the Event Aggregator. As well as simplifying registration, a Event Aggregator also simplifies the memory management issues in using observers.
## <a name="callback">Callback</a> [&#8593;](#list-of-design-patterns)
**Intent:** Callback is a piece of executable code that is passed as an argument to other code, which is expected to call back (execute) the argument at some convenient time.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/callback/etc/callback.png "Callback")
**Applicability:** Use the Callback pattern when
* When some arbitrary synchronous or asynchronous action must be performed after execution of some defined activity.
**Real world examples:**
* [CyclicBarrier] (http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/CyclicBarrier.html#CyclicBarrier%28int,%20java.lang.Runnable%29) constructor can accept callback that will be triggered every time when barrier is tripped.
## <a name="intercepting-filter">Intercepting Filter</a> [&#8593;](#list-of-design-patterns)
**Intent:** Provide pluggable filters to conduct necessary pre-processing and post-processing to requests from a client to a target
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/intercepting-filter/etc/intercepting-filter.png "Intercepting Filter")
**Applicability:** Use the Intercepting Filter pattern when
* a system uses pre-processing or post-processing requests
* a system should do the authentication/ authorization/ logging or tracking of request and then pass the requests to corresponding handlers
* you want a modular approach to configuring pre-processing and post-processing schemes
## <a name="execute-around">Execute Around</a> [&#8593;](#list-of-design-patterns)
**Intent:** Execute Around idiom frees the user from certain actions that should always be executed before and after the business method. A good example of this is resource allocation and deallocation leaving the user to specify only what to do with the resource.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/execute-around/etc/execute-around.png "Execute Around")
**Applicability:** Use the Execute Around idiom when
* You use an API that requires methods to be called in pairs such as open/close or allocate/deallocate.
## <a name="property">Property</a> [&#8593;](#list-of-design-patterns)
**Intent:** Create hierarchy of objects and new objects using already existing objects as parents.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/property/etc/property.png "Property")
**Applicability:** Use the Property pattern when
* when you like to have objects with dynamic set of fields and prototype inheritance
**Real world examples:**
* [JavaScript](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain) prototype inheritance
## <a name="poison-pill">Poison Pill</a> [&#8593;](#list-of-design-patterns)
**Intent:** Poison Pill is known predefined data item that allows to provide graceful shutdown for separate distributed consumption process.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/poison-pill/etc/poison-pill.png "Poison Pill")
**Applicability:** Use the Poison Pill idiom when
* need to send signal from one thread/process to another to terminate
**Real world examples:**
* [akka.actor.PoisonPill](http://doc.akka.io/docs/akka/2.1.4/java/untyped-actors.html)
## <a name="lazy-loading">Lazy Loading</a> [&#8593;](#list-of-design-patterns)
**Intent:** Lazy loading is a design pattern commonly used to defer initialization of an object until the point at which it is needed. It can contribute to efficiency in the program's operation if properly and appropriately used.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/lazy-loading/etc/lazy-loading.png "Lazy Loading")
**Applicability:** Use the Lazy Loading idiom when
* eager loading is expensive or the object to be loaded might not be needed at all
**Real world examples:**
* JPA annotations @OneToOne, @OneToMany, @ManyToOne, @ManyToMany and fetch = FetchType.LAZY
## <a name="service-layer">Service Layer</a> [&#8593;](#list-of-design-patterns)
**Intent:** Service Layer is an abstraction over domain logic. Typically applications require multiple kinds of interfaces to the data
they store and logic they implement: data loaders, user interfaces, integration gateways, and others. Despite their different purposes, these interfaces often need common interactions with the application to access and manipulate its data and invoke its business logic. The Service Layer fulfills this role.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/service-layer/etc/service-layer.png "Service Layer")
**Applicability:** Use the Service Layer pattern when
* you want to encapsulate domain logic under API
* you need to implement multiple interfaces with common logic and data
## <a name="specification">Specification</a> [&#8593;](#list-of-design-patterns)
**Intent:** Specification pattern separates the statement of how to match a candidate, from the
candidate object that it is matched against. As well as its usefulness in selection, it is also valuable for
validation and for building to order
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/specification/etc/specification.png "Specification")
**Applicability:** Use the Specification pattern when
* You need to select a subset of objects based on some criteria, and to refresh the selection at various times
* You need to check that only suitable objects are used for a certain role (validation)
## <a name="tolerant-reader">Tolerant Reader</a> [&#8593;](#list-of-design-patterns)
**Intent:** Tolerant Reader is an integration pattern that helps creating robust communication systems. The idea is to be as tolerant as possible when reading data from another service. This way, when the communication schema changes, the readers must not break.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/tolerant-reader/etc/tolerant-reader.png "Tolerant Reader")
**Applicability:** Use the Tolerant Reader pattern when
* The communication schema can evolve and change and yet the receiving side should not break
## <a name="model-view-controller">Model-View-Controller</a> [&#8593;](#list-of-design-patterns)
**Intent:** Separate the user interface into three interconnected components: the model, the view and the controller. Let the model manage the data, the view display the data and the controller mediate updating the data and redrawing the display.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/model-view-controller/etc/model-view-controller.png "Model-View-Controller")
**Applicability:** Use the Model-View-Controller pattern when
* you want to clearly separate the domain data from its user interface representation
## <a name="flux">Flux</a> [&#8593;](#list-of-design-patterns)
**Intent:** Flux eschews MVC in favor of a unidirectional data flow. When a user interacts with a view, the view propagates an action through a central dispatcher, to the various stores that hold the application's data and business logic, which updates all of the views that are affected.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/flux/etc/flux.png "Flux")
**Applicability:** Use the Flux pattern when
* You want to focus on creating explicit and understandable update paths for your application's data, which makes tracing changes during development simpler and makes bugs easier to track down and fix.
## <a name="double-dispatch">Double Dispatch</a> [&#8593;](#list-of-design-patterns)
**Intent:** Double Dispatch pattern is a way to create maintainable dynamic behavior based on receiver and parameter types.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/double-dispatch/etc/double-dispatch.png "Double Dispatch")
**Applicability:** Use the Double Dispatch pattern when
* The dynamic behavior is not defined only based on receiving object's type but also on the receiving method's parameter type.
**Real world examples:**
* [ObjectOutputStream](https://docs.oracle.com/javase/8/docs/api/java/io/ObjectOutputStream.html)
## <a name="multiton">Multiton</a> [&#8593;](#list-of-design-patterns)
**Intent:** Ensure a class only has limited number of instances, and provide a global point of access to them.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/multiton/etc/multiton.png "Multiton")
**Applicability:** Use the Multiton pattern when
* there must be specific number of instances of a class, and they must be accessible to clients from a well-known access point
## <a name="resource-acquisition-is-initialization">Resource Acquisition Is Initialization</a> [&#8593;](#list-of-design-patterns)
**Intent:** Resource Acquisition Is Initialization pattern can be used to implement exception safe resource management.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/resource-acquisition-is-initialization/etc/resource-acquisition-is-initialization.png "Resource Acquisition Is Initialization")
**Applicability:** Use the Resource Acquisition Is Initialization pattern when
* You have resources that must be closed in every condition
## <a name="thread-pool">Thread Pool</a> [&#8593;](#list-of-design-patterns)
**Intent:** It is often the case that tasks to be executed are short-lived and the number of tasks is large. Creating a new thread for each task would make the system spend more time creating and destroying the threads than executing the actual tasks. Thread Pool solves this problem by reusing existing threads and eliminating the latency of creating new threads.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/thread-pool/etc/thread-pool.png "Thread Pool")
**Applicability:** Use the Thread Pool pattern when
* You have a large number of short-lived tasks to be executed in parallel
## <a name="private-class-data">Private Class Data</a> [&#8593;](#list-of-design-patterns)
**Intent:** Private Class Data design pattern seeks to reduce exposure of attributes by limiting their visibility. It reduces the number of class attributes by encapsulating them in single Data object.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/private-class-data/etc/private-class-data.png "Private Class Data")
**Applicability:** Use the Private Class Data pattern when
* You want to prevent write access to class data members
## <a name="object-pool">Object Pool</a> [&#8593;](#list-of-design-patterns)
**Intent:** When objects are expensive to create and they are needed only for short periods of time it is advantageous to utilize the Object Pool pattern. The Object Pool provides a cache for instantiated objects tracking which ones are in use and which are available.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/object-pool/etc/object-pool.png "Object Pool")
**Applicability:** Use the Object Pool pattern when
* The objects are expensive to create (allocation cost)
* You need a large number of short-lived objects (memory fragmentation)
## <a name="dependency-injection">Dependency Injection</a> [&#8593;](#list-of-design-patterns)
**Intent:** Dependency Injection is a software design pattern in which one or more dependencies (or services) are injected, or passed by reference, into a dependent object (or client) and are made part of the client's state. The pattern separates the creation of a client's dependencies from its own behavior, which allows program designs to be loosely coupled and to follow the inversion of control and single responsibility principles.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/dependency-injection/etc/dependency-injection.png "Dependency Injection")
**Applicability:** Use the Dependency Injection pattern when
* When you need to remove knowledge of concrete implementation from object
* To enable unit testing of classes in isolation using mock objects or stubs
# Frequently asked questions
**<a id="Q1">Q: What is the difference between State and Strategy patterns?</a>**
While the implementation is similar they solve different problems. The State pattern deals with what state an object is in - it encapsulates state-dependent behavior. The Strategy pattern deals with how an object performs a certain task - it encapsulates an algorithm.
**<a id="Q2">Q: What is the difference between Strategy and Template Method patterns?</a>**
In Template Method the algorithm is chosen at compile time via inheritance. With Strategy pattern the algorithm is chosen at runtime via composition.
**<a id="Q3">Q: What is the difference between Proxy and Decorator patterns?</a>**
The difference is the intent of the patterns. While Proxy controls access to the object Decorator is used to add responsibilities to the object.
**<a id="Q4">Q: What is the difference between Chain of Responsibility and Intercepting Filter patterns?</a>**
While the implementations look similar there are differences. The Chain of Responsibility forms a chain of request processors and the processors are then executed one by one until the correct processor is found. In Intercepting Filter the chain is constructed from filters and the whole chain is always executed.
**<a id="Q5">Q: What is the difference between Visitor and Double Dispatch patterns?</a>**
The Visitor pattern is a means of adding a new operation to existing classes. Double dispatch is a means of dispatching function calls with respect to two polymorphic types, rather than a single polymorphic type, which is what languages like C++ and Java support directly.
**<a id="Q6">Q: What are the differences between Flyweight and Object Pool patterns?</a>**
They differ in the way they are used.
Pooled objects can simultaneously be used by a single "client" only. For that, a pooled object must be checked out from the pool, then it can be used by a client, and then the client must return the object back to the pool. Multiple instances of identical objects may exist, up to the maximal capacity of the pool.
In contrast, a Flyweight object is singleton, and it can be used simultaneously by multiple clients.
As for concurrent access, pooled objects can be mutable and they usually don't need to be thread safe, as typically, only one thread is going to use a specific instance at the same time. Flyweight must either be immutable (the best option), or implement thread safety.
As for performance and scalability, pools can become bottlenecks, if all the pooled objects are in use and more clients need them, threads will become blocked waiting for available object from the pool. This is not the case with Flyweight.
All designs should be as simple as possible. You should start with KISS, YAGNI,
and Do The Simplest Thing That Could Possibly Work principles. Complexity and
patterns should only be introduced when they are needed for practical
extensibility.
Once you are familiar with these concepts you can start drilling down into
patterns by any of the following approaches
- Using difficulty tags, `Difficulty-Beginner`, `Difficulty-Intermediate` & `Difficulty-Expert`.
- Using pattern categories, `Creational`, `Behavioral` and others.
- Search for a specific pattern. Can't find one? Please report a new pattern [here](https://github.com/iluwatar/java-design-patterns/issues).
# How to contribute
**To add a new pattern** you need to do the following steps:
1. Fork the repository.
2. Implement the code changes in your fork. Remember to add sufficient comments documenting the implementation.
3. Create a simple class diagram from your example code.
4. Add description of the pattern in README.md and link to the class diagram.
5. Create a pull request.
**To work on one of the raised issues** you need to do the following steps:
1. Fork the repository.
2. Implement the code changes in your fork. Remember to add sufficient comments documenting the implementation. Reference the issue id e.g. #52 in your commit messages.
3. Create a pull request.
**For creating/editing UML diagrams** you need [ObjectAid UML Explorer for Eclipse](http://www.objectaid.com/home).
**For inspiration** check out the following sources:
* there is a good list of design patterns at [Wikipedia](http://en.wikipedia.org/wiki/Software_design_pattern)
* Martin Fowler's [Catalog of Patterns of Enterprise Application Architecture](http://martinfowler.com/eaaCatalog/)
* [pattern language for microservices](http://microservices.io/patterns/index.html)
* Microsoft's [Cloud Design Patterns](http://download.microsoft.com/download/B/B/6/BB69622C-AB5D-4D5F-9A12-B81B952C1169/CloudDesignPatternsBook-PDF.pdf)
**Links to patterns applied in real world applications** are welcome. The links should be added to the corresponding section of the `README.md`.
# Versioning
Java-design-patterns project uses [semantic versioning](http://semver.org/) scheme.
# Credits
* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
* [Effective Java (2nd Edition)](http://www.amazon.com/Effective-Java-Edition-Joshua-Bloch/dp/0321356683)
* [Java Generics and Collections](http://www.amazon.com/Java-Generics-Collections-Maurice-Naftalin/dp/0596527756/)
* [Let’s Modify the Objects-First Approach into Design-Patterns-First](http://edu.pecinovsky.cz/papers/2006_ITiCSE_Design_Patterns_First.pdf)
* [Pattern Languages of Program Design](http://www.amazon.com/Pattern-Languages-Program-Design-Coplien/dp/0201607344/ref=sr_1_1)
* [Martin Fowler - Event Aggregator](http://martinfowler.com/eaaDev/EventAggregator.html)
* [TutorialsPoint - Intercepting Filter](http://www.tutorialspoint.com/design_pattern/intercepting_filter_pattern.htm)
* [Presentation Tier Patterns](http://www.javagyan.com/tutorials/corej2eepatterns/presentation-tier-patterns)
* [Functional Programming in Java: Harnessing the Power of Java 8 Lambda Expressions](http://www.amazon.com/Functional-Programming-Java-Harnessing-Expressions/dp/1937785467/ref=sr_1_1)
* [Martin Fowler - Service Layer](http://martinfowler.com/eaaCatalog/serviceLayer.html)
* [Martin Fowler - Specifications](http://martinfowler.com/apsupp/spec.pdf)
* [Martin Fowler - Tolerant Reader](http://martinfowler.com/bliki/TolerantReader.html)
* [Trygve Reenskaug - Model-view-controller](http://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller)
* [Flux - Application architecture for building user interfaces](http://facebook.github.io/flux/)
If you are willing to contribute to the project you will find the relevant information in our [developer wiki](https://github.com/iluwatar/java-design-patterns/wiki). We will help you and answer your questions in the [Gitter chatroom](https://gitter.im/iluwatar/java-design-patterns).
# License

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---
layout: pattern
title: Abstract Document
folder: abstract-document
permalink: /patterns/abstract-document/
categories: Structural
tags:
- Java
- Difficulty-Intermediate
---
## Intent
Achieve flexibility of untyped languages and keep the type-safety
![alt text](./etc/abstract-document-base.png "Abstract Document Base")
![alt text](./etc/abstract-document.png "Abstract Document Traits and Domain")
## Applicability
Use the Abstract Document Pattern when
* there is a need to add new properties on the fly
* you want a flexible way to organize domain in tree like structure
* you want more loosely coupled system
## Credits
* [Wikipedia: Abstract Document Pattern](https://en.wikipedia.org/wiki/Abstract_Document_Pattern)
* [Martin Fowler: Dealing with properties](http://martinfowler.com/apsupp/properties.pdf)

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<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="4" language="java" name="com.iluwatar.abstractdocument.domain.Part" project="design-patterns"
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<end type="SOURCE" refId="4"/>
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<class-diagram version="1.1.9" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
realizations="true" associations="true" dependencies="false" nesting-relationships="true" router="FAN">
<interface id="1" language="java" name="com.iluwatar.abstractdocument.Document" project="design-patterns"
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<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</interface>
<interface id="2" language="java" name="com.iluwatar.abstractdocument.domain.HasModel" project="design-patterns"
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<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</interface>
<interface id="3" language="java" name="com.iluwatar.abstractdocument.domain.HasPrice" project="design-patterns"
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<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</interface>
<interface id="4" language="java" name="com.iluwatar.abstractdocument.domain.HasParts" project="design-patterns"
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</interface>
<class id="5" language="java" name="com.iluwatar.abstractdocument.domain.Car" project="design-patterns"
file="/design-patterns/src/com/iluwatar/abstractdocument/domain/Car.java" binary="false" corner="BOTTOM_RIGHT">
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<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="6" language="java" name="com.iluwatar.abstractdocument.domain.Part" project="design-patterns"
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<realization id="7">
<end type="SOURCE" refId="5"/>
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</realization>
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<end type="TARGET" refId="2"/>
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<generalization id="9">
<end type="SOURCE" refId="2"/>
<end type="TARGET" refId="1"/>
</generalization>
<realization id="10">
<end type="SOURCE" refId="5"/>
<end type="TARGET" refId="3"/>
</realization>
<realization id="11">
<end type="SOURCE" refId="5"/>
<end type="TARGET" refId="4"/>
</realization>
<generalization id="12">
<end type="SOURCE" refId="3"/>
<end type="TARGET" refId="1"/>
</generalization>
<generalization id="13">
<end type="SOURCE" refId="4"/>
<end type="TARGET" refId="1"/>
</generalization>
<realization id="14">
<end type="SOURCE" refId="6"/>
<end type="TARGET" refId="3"/>
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<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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<association-display labels="true" multiplicity="true"/>
</class-diagram>

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<?xml version="1.0" encoding="UTF-8"?>
<!--
The MIT License
Copyright (c) 2014 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.13.0-SNAPSHOT</version>
</parent>
<artifactId>abstract-document</artifactId>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;
import java.util.function.Function;
import java.util.stream.Stream;
/**
* Abstract implementation of Document interface
*/
public abstract class AbstractDocument implements Document {
private final Map<String, Object> properties;
protected AbstractDocument(Map<String, Object> properties) {
Objects.requireNonNull(properties, "properties map is required");
this.properties = properties;
}
@Override
public Void put(String key, Object value) {
properties.put(key, value);
return null;
}
@Override
public Object get(String key) {
return properties.get(key);
}
@Override
public <T> Stream<T> children(String key, Function<Map<String, Object>, T> constructor) {
Optional<List<Map<String, Object>>> any = Stream.of(get(key)).filter(el -> el != null)
.map(el -> (List<Map<String, Object>>) el).findAny();
return any.isPresent() ? any.get().stream().map(constructor) : Stream.empty();
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append(getClass().getName()).append("[");
properties.entrySet()
.forEach(e -> builder.append("[").append(e.getKey()).append(" : ").append(e.getValue()).append("]"));
builder.append("]");
return builder.toString();
}
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument;
import com.iluwatar.abstractdocument.domain.Car;
import com.iluwatar.abstractdocument.domain.HasModel;
import com.iluwatar.abstractdocument.domain.HasParts;
import com.iluwatar.abstractdocument.domain.HasPrice;
import com.iluwatar.abstractdocument.domain.HasType;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
/**
* The Abstract Document pattern enables handling additional, non-static
* properties. This pattern uses concept of traits to enable type safety and
* separate properties of different classes into set of interfaces.
* <p>
* <p>
* In Abstract Document pattern,({@link AbstractDocument}) fully implements
* {@link Document}) interface. Traits are then defined to enable access to
* properties in usual, static way.
*/
public class App {
/**
* Executes the App
*/
public App() {
System.out.println("Constructing parts and car");
Map<String, Object> carProperties = new HashMap<>();
carProperties.put(HasModel.PROPERTY, "300SL");
carProperties.put(HasPrice.PROPERTY, 10000L);
Map<String, Object> wheelProperties = new HashMap<>();
wheelProperties.put(HasType.PROPERTY, "wheel");
wheelProperties.put(HasModel.PROPERTY, "15C");
wheelProperties.put(HasPrice.PROPERTY, 100L);
Map<String, Object> doorProperties = new HashMap<>();
doorProperties.put(HasType.PROPERTY, "door");
doorProperties.put(HasModel.PROPERTY, "Lambo");
doorProperties.put(HasPrice.PROPERTY, 300L);
carProperties.put(HasParts.PROPERTY, Arrays.asList(wheelProperties, doorProperties));
Car car = new Car(carProperties);
System.out.println("Here is our car:");
System.out.println("-> model: " + car.getModel().get());
System.out.println("-> price: " + car.getPrice().get());
System.out.println("-> parts: ");
car.getParts().forEach(p -> System.out
.println("\t" + p.getType().get() + "/" + p.getModel().get() + "/" + p.getPrice().get()));
}
/**
* Program entry point
*
* @param args command line args
*/
public static void main(String[] args) {
new App();
}
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Stream;
/**
* Document interface
*/
public interface Document {
/**
* Puts the value related to the key
*
* @param key element key
* @param value element value
* @return Void
*/
Void put(String key, Object value);
/**
* Gets the value for the key
*
* @param key element key
* @return value or null
*/
Object get(String key);
/**
* Gets the stream of child documents
*
* @param key element key
* @param constructor constructor of child class
* @return child documents
*/
<T> Stream<T> children(String key, Function<Map<String, Object>, T> constructor);
}

38
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument.domain;
import java.util.Map;
import com.iluwatar.abstractdocument.AbstractDocument;
/**
* Car entity
*/
public class Car extends AbstractDocument implements HasModel, HasPrice, HasParts {
public Car(Map<String, Object> properties) {
super(properties);
}
}

40
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument.domain;
import java.util.Optional;
import com.iluwatar.abstractdocument.Document;
/**
* HasModel trait for static access to 'model' property
*/
public interface HasModel extends Document {
String PROPERTY = "model";
default Optional<String> getModel() {
return Optional.ofNullable((String) get(PROPERTY));
}
}

40
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument.domain;
import java.util.stream.Stream;
import com.iluwatar.abstractdocument.Document;
/**
* HasParts trait for static access to 'parts' property
*/
public interface HasParts extends Document {
String PROPERTY = "parts";
default Stream<Part> getParts() {
return children(PROPERTY, Part::new);
}
}

40
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument.domain;
import java.util.Optional;
import com.iluwatar.abstractdocument.Document;
/**
* HasPrice trait for static access to 'price' property
*/
public interface HasPrice extends Document {
String PROPERTY = "price";
default Optional<Number> getPrice() {
return Optional.ofNullable((Number) get(PROPERTY));
}
}

40
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument.domain;
import com.iluwatar.abstractdocument.Document;
import java.util.Optional;
/**
* HasType trait for static access to 'type' property
*/
public interface HasType extends Document {
String PROPERTY = "type";
default Optional<String> getType() {
return Optional.ofNullable((String) get(PROPERTY));
}
}

38
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument.domain;
import java.util.Map;
import com.iluwatar.abstractdocument.AbstractDocument;
/**
* Part entity
*/
public class Part extends AbstractDocument implements HasType, HasModel, HasPrice {
public Part(Map<String, Object> properties) {
super(properties);
}
}

88
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument;
import org.junit.Test;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Stream;
import static junit.framework.TestCase.assertEquals;
import static junit.framework.TestCase.assertNotNull;
/**
* AbstractDocument test class
*/
public class AbstractDocumentTest {
private static final String KEY = "key";
private static final String VALUE = "value";
private class DocumentImplementation extends AbstractDocument {
DocumentImplementation(Map<String, Object> properties) {
super(properties);
}
}
private DocumentImplementation document = new DocumentImplementation(new HashMap<>());
@Test
public void shouldPutAndGetValue() {
document.put(KEY, VALUE);
assertEquals(VALUE, document.get(KEY));
}
@Test
public void shouldRetrieveChildren() {
Map<String, Object> child1 = new HashMap<>();
Map<String, Object> child2 = new HashMap<>();
List<Map<String, Object>> children = Arrays.asList(child1, child2);
document.put(KEY, children);
Stream<DocumentImplementation> childrenStream = document.children(KEY, DocumentImplementation::new);
assertNotNull(children);
assertEquals(2, childrenStream.count());
}
@Test
public void shouldRetrieveEmptyStreamForNonExistingChildren() {
Stream<DocumentImplementation> children = document.children(KEY, DocumentImplementation::new);
assertNotNull(children);
assertEquals(0, children.count());
}
@Test
public void shouldIncludePropsInToString() {
Map<String, Object> props = new HashMap<>();
props.put(KEY, VALUE);
DocumentImplementation document = new DocumentImplementation(props);
assertNotNull(document.toString().contains(KEY));
assertNotNull(document.toString().contains(VALUE));
}
}

37
abstract-document/src/test/java/com/iluwatar/abstractdocument/AppTest.java Normal file
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument;
import org.junit.Test;
/**
* Simple App test
*/
public class AppTest {
@Test
public void shouldExecuteAppWithoutException() {
App.main(null);
}
}

77
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractdocument;
import com.iluwatar.abstractdocument.domain.Car;
import com.iluwatar.abstractdocument.domain.HasModel;
import com.iluwatar.abstractdocument.domain.HasParts;
import com.iluwatar.abstractdocument.domain.HasPrice;
import com.iluwatar.abstractdocument.domain.HasType;
import com.iluwatar.abstractdocument.domain.Part;
import org.junit.Test;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import static junit.framework.TestCase.assertEquals;
/**
* Test for Part and Car
*/
public class DomainTest {
private static final String TEST_PART_TYPE = "test-part-type";
private static final String TEST_PART_MODEL = "test-part-model";
private static final long TEST_PART_PRICE = 0L;
private static final String TEST_CAR_MODEL = "test-car-model";
private static final long TEST_CAR_PRICE = 1L;
@Test
public void shouldConstructPart() {
Map<String, Object> partProperties = new HashMap<>();
partProperties.put(HasType.PROPERTY, TEST_PART_TYPE);
partProperties.put(HasModel.PROPERTY, TEST_PART_MODEL);
partProperties.put(HasPrice.PROPERTY, TEST_PART_PRICE);
Part part = new Part(partProperties);
assertEquals(TEST_PART_TYPE, part.getType().get());
assertEquals(TEST_PART_MODEL, part.getModel().get());
assertEquals(TEST_PART_PRICE, part.getPrice().get());
}
@Test
public void shouldConstructCar() {
Map<String, Object> carProperties = new HashMap<>();
carProperties.put(HasModel.PROPERTY, TEST_CAR_MODEL);
carProperties.put(HasPrice.PROPERTY, TEST_CAR_PRICE);
carProperties.put(HasParts.PROPERTY, Arrays.asList(new HashMap<>(), new HashMap<>()));
Car car = new Car(carProperties);
assertEquals(TEST_CAR_MODEL, car.getModel().get());
assertEquals(TEST_CAR_PRICE, car.getPrice().get());
assertEquals(2, car.getParts().count());
}
}

36
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---
layout: pattern
title: Abstract Factory
folder: abstract-factory
permalink: /patterns/abstract-factory/
categories: Creational
tags:
- Java
- Gang Of Four
- Difficulty-Intermediate
---
## Also known as
Kit
## Intent
Provide an interface for creating families of related or dependent
objects without specifying their concrete classes.
![alt text](./etc/abstract-factory_1.png "Abstract Factory")
## Applicability
Use the Abstract Factory pattern when
* a system should be independent of how its products are created, composed and represented
* a system should be configured with one of multiple families of products
* a family of related product objects is designed to be used together, and you need to enforce this constraint
* you want to provide a class library of products, and you want to reveal just their interfaces, not their implementations
## Real world examples
* [javax.xml.parsers.DocumentBuilderFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/parsers/DocumentBuilderFactory.html)
## Credits
* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)

26
abstract-factory/pom.xml
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@ -1,11 +1,35 @@
<?xml version="1.0"?>
<!--
The MIT License
Copyright (c) 2014 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.1.0</version>
<version>1.13.0-SNAPSHOT</version>
</parent>
<artifactId>abstract-factory</artifactId>
<dependencies>

144
abstract-factory/src/main/java/com/iluwatar/abstractfactory/App.java
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@ -1,29 +1,115 @@
package com.iluwatar.abstractfactory;
/**
*
* The essence of the Abstract Factory pattern is a factory interface
* (KingdomFactory) and its implementations (ElfKingdomFactory,
* OrcKingdomFactory).
*
* The example uses both concrete implementations to create a king, a castle and
* an army.
*
*/
public class App {
public static void main(String[] args) {
createKingdom(new ElfKingdomFactory());
createKingdom(new OrcKingdomFactory());
}
public static void createKingdom(KingdomFactory factory) {
King king = factory.createKing();
Castle castle = factory.createCastle();
Army army = factory.createArmy();
System.out.println("The kingdom was created.");
System.out.println(king);
System.out.println(castle);
System.out.println(army);
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* The Abstract Factory pattern provides a way to encapsulate a group of individual factories that have a common theme
* without specifying their concrete classes. In normal usage, the client software creates a concrete implementation of
* the abstract factory and then uses the generic interface of the factory to create the concrete objects that are part
* of the theme. The client does not know (or care) which concrete objects it gets from each of these internal
* factories, since it uses only the generic interfaces of their products. This pattern separates the details of
* implementation of a set of objects from their general usage and relies on object composition, as object creation is
* implemented in methods exposed in the factory interface.
* <p>
* The essence of the Abstract Factory pattern is a factory interface ({@link KingdomFactory}) and its implementations (
* {@link ElfKingdomFactory}, {@link OrcKingdomFactory}). The example uses both concrete implementations to create a
* king, a castle and an army.
*
*/
public class App {
private King king;
private Castle castle;
private Army army;
/**
* Creates kingdom
*/
public void createKingdom(final KingdomFactory factory) {
setKing(factory.createKing());
setCastle(factory.createCastle());
setArmy(factory.createArmy());
}
King getKing(final KingdomFactory factory) {
return factory.createKing();
}
public King getKing() {
return king;
}
private void setKing(final King king) {
this.king = king;
}
Castle getCastle(final KingdomFactory factory) {
return factory.createCastle();
}
public Castle getCastle() {
return castle;
}
private void setCastle(final Castle castle) {
this.castle = castle;
}
Army getArmy(final KingdomFactory factory) {
return factory.createArmy();
}
public Army getArmy() {
return army;
}
private void setArmy(final Army army) {
this.army = army;
}
/**
* Program entry point
*
* @param args
* command line args
*/
public static void main(String[] args) {
App app = new App();
System.out.println("Elf Kingdom");
app.createKingdom(new ElfKingdomFactory());
System.out.println(app.getArmy().getDescription());
System.out.println(app.getCastle().getDescription());
System.out.println(app.getKing().getDescription());
System.out.println("\nOrc Kingdom");
app.createKingdom(new OrcKingdomFactory());
System.out.println(app.getArmy().getDescription());
System.out.println(app.getCastle().getDescription());
System.out.println(app.getKing().getDescription());
}
}

38
abstract-factory/src/main/java/com/iluwatar/abstractfactory/Army.java
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@ -1,5 +1,33 @@
package com.iluwatar.abstractfactory;
public interface Army {
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* Army interface
*
*/
public interface Army {
String getDescription();
}

38
abstract-factory/src/main/java/com/iluwatar/abstractfactory/Castle.java
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@ -1,5 +1,33 @@
package com.iluwatar.abstractfactory;
public interface Castle {
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* Castle interface
*
*/
public interface Castle {
String getDescription();
}

48
abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfArmy.java
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@ -1,10 +1,38 @@
package com.iluwatar.abstractfactory;
public class ElfArmy implements Army {
@Override
public String toString() {
return "This is the Elven Army!";
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* ElfArmy
*
*/
public class ElfArmy implements Army {
static final String DESCRIPTION = "This is the Elven Army!";
@Override
public String getDescription() {
return DESCRIPTION;
}
}

48
abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfCastle.java
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@ -1,10 +1,38 @@
package com.iluwatar.abstractfactory;
public class ElfCastle implements Castle {
@Override
public String toString() {
return "This is the Elven castle!";
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* ElfCastle
*
*/
public class ElfCastle implements Castle {
static final String DESCRIPTION = "This is the Elven castle!";
@Override
public String getDescription() {
return DESCRIPTION;
}
}

48
abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfKing.java
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@ -1,10 +1,38 @@
package com.iluwatar.abstractfactory;
public class ElfKing implements King {
@Override
public String toString() {
return "This is the Elven king!";
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* ElfKing
*
*/
public class ElfKing implements King {
static final String DESCRIPTION = "This is the Elven king!";
@Override
public String getDescription() {
return DESCRIPTION;
}
}

66
abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfKingdomFactory.java
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@ -1,22 +1,44 @@
package com.iluwatar.abstractfactory;
/**
*
* Concrete factory.
*
*/
public class ElfKingdomFactory implements KingdomFactory {
public Castle createCastle() {
return new ElfCastle();
}
public King createKing() {
return new ElfKing();
}
public Army createArmy() {
return new ElfArmy();
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* ElfKingdomFactory concrete factory.
*
*/
public class ElfKingdomFactory implements KingdomFactory {
public Castle createCastle() {
return new ElfCastle();
}
public King createKing() {
return new ElfKing();
}
public Army createArmy() {
return new ElfArmy();
}
}

38
abstract-factory/src/main/java/com/iluwatar/abstractfactory/King.java
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@ -1,5 +1,33 @@
package com.iluwatar.abstractfactory;
public interface King {
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* King interface
*
*/
public interface King {
String getDescription();
}

54
abstract-factory/src/main/java/com/iluwatar/abstractfactory/KingdomFactory.java
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@ -1,16 +1,38 @@
package com.iluwatar.abstractfactory;
/**
*
* The factory interface.
*
*/
public interface KingdomFactory {
Castle createCastle();
King createKing();
Army createArmy();
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* KingdomFactory factory interface.
*
*/
public interface KingdomFactory {
Castle createCastle();
King createKing();
Army createArmy();
}

48
abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcArmy.java
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@ -1,10 +1,38 @@
package com.iluwatar.abstractfactory;
public class OrcArmy implements Army {
@Override
public String toString() {
return "This is the Orcish Army!";
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* OrcArmy
*
*/
public class OrcArmy implements Army {
static final String DESCRIPTION = "This is the Orc Army!";
@Override
public String getDescription() {
return DESCRIPTION;
}
}

48
abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcCastle.java
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@ -1,10 +1,38 @@
package com.iluwatar.abstractfactory;
public class OrcCastle implements Castle {
@Override
public String toString() {
return "This is the Orcish castle!";
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* OrcCastle
*
*/
public class OrcCastle implements Castle {
static final String DESCRIPTION = "This is the Orc castle!";
@Override
public String getDescription() {
return DESCRIPTION;
}
}

48
abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcKing.java
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@ -1,10 +1,38 @@
package com.iluwatar.abstractfactory;
public class OrcKing implements King {
@Override
public String toString() {
return "This is the Orc king!";
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* OrcKing
*
*/
public class OrcKing implements King {
static final String DESCRIPTION = "This is the Orc king!";
@Override
public String getDescription() {
return DESCRIPTION;
}
}

65
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@ -1,22 +1,43 @@
package com.iluwatar.abstractfactory;
/**
*
* Concrete factory.
*
*/
public class OrcKingdomFactory implements KingdomFactory {
public Castle createCastle() {
return new OrcCastle();
}
public King createKing() {
return new OrcKing();
}
public Army createArmy() {
return new OrcArmy();
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
/**
*
* OrcKingdomFactory concrete factory.
*
*/
public class OrcKingdomFactory implements KingdomFactory {
public Castle createCastle() {
return new OrcCastle();
}
public King createKing() {
return new OrcKing();
}
public Army createArmy() {
return new OrcArmy();
}
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import org.junit.Before;
import org.junit.Test;
public class AbstractFactoryTest {
private App app = new App();
private KingdomFactory elfFactory;
private KingdomFactory orcFactory;
@Before
public void setUp() {
elfFactory = new ElfKingdomFactory();
orcFactory = new OrcKingdomFactory();
}
@Test
public void king() {
final King elfKing = app.getKing(elfFactory);
assertTrue(elfKing instanceof ElfKing);
assertEquals(ElfKing.DESCRIPTION, elfKing.getDescription());
final King orcKing = app.getKing(orcFactory);
assertTrue(orcKing instanceof OrcKing);
assertEquals(OrcKing.DESCRIPTION, orcKing.getDescription());
}
@Test
public void castle() {
final Castle elfCastle = app.getCastle(elfFactory);
assertTrue(elfCastle instanceof ElfCastle);
assertEquals(ElfCastle.DESCRIPTION, elfCastle.getDescription());
final Castle orcCastle = app.getCastle(orcFactory);
assertTrue(orcCastle instanceof OrcCastle);
assertEquals(OrcCastle.DESCRIPTION, orcCastle.getDescription());
}
@Test
public void army() {
final Army elfArmy = app.getArmy(elfFactory);
assertTrue(elfArmy instanceof ElfArmy);
assertEquals(ElfArmy.DESCRIPTION, elfArmy.getDescription());
final Army orcArmy = app.getArmy(orcFactory);
assertTrue(orcArmy instanceof OrcArmy);
assertEquals(OrcArmy.DESCRIPTION, orcArmy.getDescription());
}
@Test
public void createElfKingdom() {
app.createKingdom(elfFactory);
final King king = app.getKing();
final Castle castle = app.getCastle();
final Army army = app.getArmy();
assertTrue(king instanceof ElfKing);
assertEquals(ElfKing.DESCRIPTION, king.getDescription());
assertTrue(castle instanceof ElfCastle);
assertEquals(ElfCastle.DESCRIPTION, castle.getDescription());
assertTrue(army instanceof ElfArmy);
assertEquals(ElfArmy.DESCRIPTION, army.getDescription());
}
@Test
public void createOrcKingdom() {
app.createKingdom(orcFactory);
final King king = app.getKing();
final Castle castle = app.getCastle();
final Army army = app.getArmy();
assertTrue(king instanceof OrcKing);
assertEquals(OrcKing.DESCRIPTION, king.getDescription());
assertTrue(castle instanceof OrcCastle);
assertEquals(OrcCastle.DESCRIPTION, castle.getDescription());
assertTrue(army instanceof OrcArmy);
assertEquals(OrcArmy.DESCRIPTION, army.getDescription());
}
}

51
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@ -1,13 +1,38 @@
package com.iluwatar.abstractfactory;
import org.junit.Test;
import com.iluwatar.abstractfactory.App;
public class AppTest {
@Test
public void test() {
String[] args = {};
App.main(args);
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.abstractfactory;
import org.junit.Test;
import java.io.IOException;
/**
* Tests that Abstract Factory example runs without errors.
*/
public class AppTest {
@Test
public void test() throws IOException {
String[] args = {};
App.main(args);
}
}

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---
layout: pattern
title: Adapter
folder: adapter
permalink: /patterns/adapter/
categories: Structural
tags:
- Java
- Gang Of Four
- Difficulty-Beginner
---
## Also known as
Wrapper
## Intent
Convert the interface of a class into another interface the clients
expect. Adapter lets classes work together that couldn't otherwise because of
incompatible interfaces.
![alt text](./etc/adapter.png "Adapter")
## Applicability
Use the Adapter pattern when
* you want to use an existing class, and its interface does not match the one you need
* you want to create a reusable class that cooperates with unrelated or unforeseen classes, that is, classes that don't necessarily have compatible interfaces
* you need to use several existing subclasses, but it's impractical to adapt their interface by subclassing every one. An object adapter can adapt the interface of its parent class.
## Real world examples
* [java.util.Arrays#asList()](http://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#asList%28T...%29)
## Credits
* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
* [J2EE Design Patterns](http://www.amazon.com/J2EE-Design-Patterns-William-Crawford/dp/0596004273/ref=sr_1_2)

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<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
realizations="true" associations="true" dependencies="false" nesting-relationships="true">
<class id="1" language="java" name="com.iluwatar.adapter.GnomeEngineeringManager" project="adapter"
file="/adapter/src/main/java/com/iluwatar/adapter/GnomeEngineeringManager.java" binary="false" corner="BOTTOM_RIGHT">
<position height="106" width="224" x="110" y="210"/>
<class-diagram version="1.1.9" icons="true" always-add-relationships="false" generalizations="true" realizations="true"
associations="true" dependencies="false" nesting-relationships="true" router="FAN">
<class id="1" language="java" name="com.iluwatar.adapter.FishingBoat" project="adapter"
file="/adapter/src/main/java/com/iluwatar/adapter/FishingBoat.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="656" y="355"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<interface id="2" language="java" name="com.iluwatar.adapter.Engineer" project="adapter"
file="/adapter/src/main/java/com/iluwatar/adapter/Engineer.java" binary="false" corner="BOTTOM_RIGHT">
<position height="88" width="141" x="110" y="356"/>
<class id="2" language="java" name="com.iluwatar.adapter.Captain" project="adapter"
file="/adapter/src/main/java/com/iluwatar/adapter/Captain.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="228" y="185"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="3" language="java" name="com.iluwatar.adapter.BattleFishingBoat" project="adapter"
file="/adapter/src/main/java/com/iluwatar/adapter/BattleFishingBoat.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="463" y="357"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<interface id="4" language="java" name="com.iluwatar.adapter.BattleShip" project="adapter"
file="/adapter/src/main/java/com/iluwatar/adapter/BattleShip.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="466" y="170"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</interface>
<class id="3" language="java" name="com.iluwatar.adapter.GnomeEngineer" project="adapter"
file="/adapter/src/main/java/com/iluwatar/adapter/GnomeEngineer.java" binary="false" corner="BOTTOM_RIGHT">
<position height="106" width="141" x="374" y="210"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="4" language="java" name="com.iluwatar.adapter.GoblinGlider" project="adapter"
file="/adapter/src/main/java/com/iluwatar/adapter/GoblinGlider.java" binary="false" corner="BOTTOM_RIGHT">
<position height="142" width="130" x="374" y="356"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<realization id="5">
<end type="SOURCE" refId="1"/>
<end type="TARGET" refId="2"/>
<end type="SOURCE" refId="2"/>
<end type="TARGET" refId="4"/>
</realization>
<realization id="6">
<end type="SOURCE" refId="3"/>
<end type="TARGET" refId="2"/>
</realization>
<association id="7">
<end type="SOURCE" refId="1" navigable="false">
<attribute id="8" name="engineer"/>
<multiplicity id="9" minimum="0" maximum="1"/>
<association id="6">
<end type="SOURCE" refId="3" navigable="false">
<attribute id="7" name="boat"/>
<multiplicity id="8" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="2" navigable="true"/>
<end type="TARGET" refId="1" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<realization id="9">
<end type="SOURCE" refId="3"/>
<end type="TARGET" refId="4"/>
</realization>
<association id="10">
<end type="SOURCE" refId="3" navigable="false">
<attribute id="11" name="glider"/>
<end type="SOURCE" refId="2" navigable="false">
<attribute id="11" name="battleship"/>
<multiplicity id="12" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="4" navigable="true"/>

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<?xml version="1.0"?>
<!--
The MIT License
Copyright (c) 2014 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.1.0</version>
<version>1.13.0-SNAPSHOT</version>
</parent>
<artifactId>adapter</artifactId>
<dependencies>
@ -14,5 +38,10 @@
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-core</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>

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package com.iluwatar.adapter;
/**
*
* There are two variations of the Adapter pattern: The class adapter implements
* the adaptee's interface whereas the object adapter uses composition to
* contain the adaptee in the adapter object. This example uses the object
* adapter approach.
*
* The Adapter (GnomeEngineer) converts the interface of the target class
* (GoblinGlider) into a suitable one expected by the client
* (GnomeEngineeringManager).
*
*/
public class App {
public static void main(String[] args) {
Engineer manager = new GnomeEngineeringManager();
manager.operateDevice();
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.adapter;
/**
* An adapter helps two incompatible interfaces to work together. This is the real world definition
* for an adapter. Interfaces may be incompatible but the inner functionality should suit the need.
* The Adapter design pattern allows otherwise incompatible classes to work together by converting
* the interface of one class into an interface expected by the clients.
*
* <p>
* There are two variations of the Adapter pattern: The class adapter implements the adaptee's
* interface whereas the object adapter uses composition to contain the adaptee in the adapter
* object. This example uses the object adapter approach.
*
* <p>
* The Adapter ({@link BattleFishingBoat}) converts the interface of the adaptee class (
* {@link FishingBoat}) into a suitable one expected by the client ( {@link BattleShip} ).
*
* <p>
* The story of this implementation is this. <br>
* Pirates are coming! we need a {@link BattleShip} to fight! We have a {@link FishingBoat} and our
* captain. We have no time to make up a new ship! we need to reuse this {@link FishingBoat}. The
* captain needs a battleship which can fire and move. The spec is in {@link BattleShip}. We will
* use the Adapter pattern to reuse {@link FishingBoat}.
*
*/
public class App {
/**
* Program entry point.
*
* @param args command line args
*/
public static void main(String[] args) {
Captain captain = new Captain(new BattleFishingBoat());
captain.move();
captain.fire();
}
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.adapter;
/**
*
* Adapter class. Adapts the interface of the device ({@link FishingBoat}) into {@link BattleShip}
* interface expected by the client ({@link Captain}). <br>
* In this case we added a new function fire to suit the interface. We are reusing the
* {@link FishingBoat} without changing itself. The Adapter class can just map the functions of the
* Adaptee or add, delete features of the Adaptee.
*
*/
public class BattleFishingBoat implements BattleShip {
private FishingBoat boat;
public BattleFishingBoat() {
boat = new FishingBoat();
}
@Override
public void fire() {
System.out.println("fire!");
}
@Override
public void move() {
boat.sail();
}
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.adapter;
/**
* The interface expected by the client.<br>
* A Battleship can fire and move.
*
*/
public interface BattleShip {
void fire();
void move();
}

55
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.adapter;
/**
* The Captain uses {@link BattleShip} to fight. <br>
* This is the client in the pattern.
*/
public class Captain implements BattleShip {
private BattleShip battleship;
public Captain() {
}
public Captain(BattleShip battleship) {
this.battleship = battleship;
}
public void setBattleship(BattleShip battleship) {
this.battleship = battleship;
}
@Override
public void fire() {
battleship.fire();
}
@Override
public void move() {
battleship.move();
}
}

12
adapter/src/main/java/com/iluwatar/adapter/Engineer.java
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@ -1,12 +0,0 @@
package com.iluwatar.adapter;
/**
*
* Engineers can operate devices.
*
*/
public interface Engineer {
void operateDevice();
}

40
adapter/src/main/java/com/iluwatar/adapter/FishingBoat.java Normal file
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.adapter;
/**
*
* Device class (adaptee in the pattern). We want to reuse this class
*
*/
public class FishingBoat {
public void sail() {
System.out.println("The Boat is moving to that place");
}
public void fish() {
System.out.println("fishing ...");
}
}

24
adapter/src/main/java/com/iluwatar/adapter/GnomeEngineer.java
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@ -1,24 +0,0 @@
package com.iluwatar.adapter;
/**
*
* Adapter class. Adapts the interface of the device (GoblinGlider) into
* Engineer interface expected by the client (GnomeEngineeringManager).
*
*/
public class GnomeEngineer implements Engineer {
private GoblinGlider glider;
public GnomeEngineer() {
glider = new GoblinGlider();
}
@Override
public void operateDevice() {
glider.attachGlider();
glider.gainSpeed();
glider.takeOff();
}
}

20
adapter/src/main/java/com/iluwatar/adapter/GnomeEngineeringManager.java
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@ -1,20 +0,0 @@
package com.iluwatar.adapter;
/**
*
* GnomeEngineering manager uses Engineer to operate devices.
*
*/
public class GnomeEngineeringManager implements Engineer {
private Engineer engineer;
public GnomeEngineeringManager() {
engineer = new GnomeEngineer();
}
@Override
public void operateDevice() {
engineer.operateDevice();
}
}

21
adapter/src/main/java/com/iluwatar/adapter/GoblinGlider.java
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@ -1,21 +0,0 @@
package com.iluwatar.adapter;
/**
*
* Device class (adaptee in the pattern).
*
*/
public class GoblinGlider {
public void attachGlider() {
System.out.println("Glider attached.");
}
public void gainSpeed() {
System.out.println("Gaining speed.");
}
public void takeOff() {
System.out.println("Lift-off!");
}
}

83
adapter/src/test/java/com/iluwatar/adapter/AdapterPatternTest.java Normal file
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.adapter;
import org.junit.Before;
import org.junit.Test;
import java.util.HashMap;
import java.util.Map;
import static org.mockito.Mockito.spy;
import static org.mockito.Mockito.verify;
/**
* Test class
*
*/
public class AdapterPatternTest {
private Map<String, Object> beans;
private static final String BATTLESHIP_BEAN = "engineer";
private static final String CAPTAIN_BEAN = "captain";
/**
* This method runs before the test execution and sets the bean objects in the beans Map.
*/
@Before
public void setup() {
beans = new HashMap<>();
BattleFishingBoat battleFishingBoat = spy(new BattleFishingBoat());
beans.put(BATTLESHIP_BEAN, battleFishingBoat);
Captain captain = new Captain();
captain.setBattleship((BattleFishingBoat) beans.get(BATTLESHIP_BEAN));
beans.put(CAPTAIN_BEAN, captain);
}
/**
* This test asserts that when we use the move() method on a captain bean(client), it is
* internally calling move method on the battleship object. The Adapter ({@link BattleFishingBoat}
* ) converts the interface of the target class ( {@link FishingBoat}) into a suitable one
* expected by the client ({@link Captain} ).
*/
@Test
public void testAdapter() {
BattleShip captain = (BattleShip) beans.get(CAPTAIN_BEAN);
// when captain moves
captain.move();
// the captain internally calls the battleship object to move
BattleShip battleship = (BattleShip) beans.get(BATTLESHIP_BEAN);
verify(battleship).move();
// same with above with firing
captain.fire();
verify(battleship).fire();
}
}

52
adapter/src/test/java/com/iluwatar/adapter/AppTest.java
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@ -1,14 +1,38 @@
package com.iluwatar.adapter;
import org.junit.Test;
import com.iluwatar.adapter.App;
public class AppTest {
@Test
public void test() {
String[] args = {};
App.main(args);
}
}
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.adapter;
import org.junit.Test;
import java.io.IOException;
/**
* Tests that Adapter example runs without errors.
*/
public class AppTest {
@Test
public void test() throws IOException {
String[] args = {};
App.main(args);
}
}

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aggregator-microservices/README.md Normal file
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---
layout: pattern
title: Aggregator Microservices
folder: aggregator-microservices
permalink: /patterns/aggregator-microservices/
categories: Architectural
tags:
- Java
- Spring
---
## Intent
The user makes a single call to the Aggregator, and the aggregator then calls each relevant microservice and collects
the data, apply business logic to it, and further publish is as a REST Endpoint.
More variations of the aggregator are:
- Proxy Microservice Design Pattern: A different microservice is called upon the business need.
- Chained Microservice Design Pattern: In this case each microservice is dependent/ chained to a series
of other microservices.
![alt text](./etc/aggregator-microservice.png "Aggregator Microservice")
## Applicability
Use the Aggregator Microservices pattern when you need a unified API for various microservices, regardless the client device.
## Credits
* [Microservice Design Patterns](http://blog.arungupta.me/microservice-design-patterns/)

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aggregator-microservices/aggregator-service/pom.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<!--
The MIT License
Copyright (c) 2014 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>aggregator-microservices</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.13.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>aggregator-service</artifactId>
<packaging>jar</packaging>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-core</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>${spring-boot.version}</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>

58
aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/Aggregator.java Normal file
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.aggregator.microservices;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.annotation.Resource;
/**
* The aggregator aggregates calls on various micro-services, collects
* data and further publishes them under a REST endpoint.
*/
@RestController
public class Aggregator {
@Resource
private ProductInformationClient informationClient;
@Resource
private ProductInventoryClient inventoryClient;
/**
* Retrieves product data.
*
* @return a Product.
*/
@RequestMapping("/product")
public Product getProduct() {
Product product = new Product();
product.setTitle(informationClient.getProductTitle());
product.setProductInventories(inventoryClient.getProductInventories());
return product;
}
}

39
aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/App.java Normal file
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.aggregator.microservices;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class App {
/**
* Program entry point
*
* @param args command line args
*/
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}

57
aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/Product.java Normal file
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.aggregator.microservices;
/**
* Encapsulates all the data for a Product that clients will request.
*/
public class Product {
/**
* The title of the product.
*/
private String title;
/**
* The inventories of the product.
*/
private int productInventories;
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public int getProductInventories() {
return productInventories;
}
public void setProductInventories(int productInventories) {
this.productInventories = productInventories;
}
}

32
aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/ProductInformationClient.java Normal file
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.aggregator.microservices;
/**
* Interface for the Information micro-service.
*/
public interface ProductInformationClient {
String getProductTitle();
}

53
aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/ProductInformationClientImpl.java Normal file
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.aggregator.microservices;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.springframework.stereotype.Component;
import java.io.IOException;
/**
* An adapter to communicate with information micro-service.
*/
@Component
public class ProductInformationClientImpl implements ProductInformationClient {
@Override
public String getProductTitle() {
String response = null;
try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
HttpGet httpGet = new HttpGet("http://localhost:51515/information");
try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
response = EntityUtils.toString(httpResponse.getEntity());
}
} catch (IOException e) {
e.printStackTrace();
}
return response;
}
}

31
aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/ProductInventoryClient.java Normal file
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.aggregator.microservices;
/**
* Interface to Inventory micro-service.
*/
public interface ProductInventoryClient {
int getProductInventories();
}

53
aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/ProductInventoryClientImpl.java Normal file
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.aggregator.microservices;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.springframework.stereotype.Component;
import java.io.IOException;
/**
* An adapter to communicate with inventory micro-service.
*/
@Component
public class ProductInventoryClientImpl implements ProductInventoryClient {
@Override
public int getProductInventories() {
String response = "0";
try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
HttpGet httpGet = new HttpGet("http://localhost:51516/inventories");
try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
response = EntityUtils.toString(httpResponse.getEntity());
}
} catch (IOException e) {
e.printStackTrace();
}
return Integer.parseInt(response);
}
}

24
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#
# The MIT License
# Copyright (c) 2014 Ilkka Seppälä
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
server.port=50004

67
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.aggregator.microservices;
import org.junit.Before;
import org.junit.Test;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.when;
public class AggregatorTest {
@InjectMocks
private Aggregator aggregator;
@Mock
private ProductInformationClient informationClient;
@Mock
private ProductInventoryClient inventoryClient;
@Before
public void setup() {
MockitoAnnotations.initMocks(this);
}
/**
* Tests getting the data for a desktop client
*/
@Test
public void testGetProduct() {
String title = "The Product Title.";
int inventories = 5;
when(informationClient.getProductTitle()).thenReturn(title);
when(inventoryClient.getProductInventories()).thenReturn(inventories);
Product testProduct = aggregator.getProduct();
assertEquals(title, testProduct.getTitle());
assertEquals(inventories, testProduct.getProductInventories());
}
}

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<?xml version="1.0" encoding="UTF-8"?>
<!--
The MIT License
Copyright (c) 2014 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>aggregator-microservices</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.13.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>information-microservice</artifactId>
<packaging>jar</packaging>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>${spring-boot.version}</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.information.microservice;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/**
* Inventory Application starts container (Spring Boot) and exposes the Inventory micro-service.
*/
@SpringBootApplication
public class InformationApplication {
public static void main(String[] args) {
SpringApplication.run(InformationApplication.class, args);
}
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.information.microservice;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class InformationController {
/**
* Endpoint to retrieve a product's informations.
*
* @return product inventory.
*/
@RequestMapping(value = "/information", method = RequestMethod.GET)
public String getProductTitle() {
return "The Product Title.";
}
}

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#
# The MIT License
# Copyright (c) 2014 Ilkka Seppälä
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
server.port=51515

39
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.information.microservice;
import org.junit.Assert;
import org.junit.Test;
public class InformationControllerTest {
@Test
public void shouldGetProductTitle() {
InformationController infoController = new InformationController();
String title = infoController.getProductTitle();
Assert.assertEquals("The Product Title.", title);
}
}

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<?xml version="1.0" encoding="UTF-8"?>
<!--
The MIT License
Copyright (c) 2014 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>aggregator-microservices</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.13.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>inventory-microservice</artifactId>
<packaging>jar</packaging>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>${spring-boot.version}</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>

38
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.inventory.microservice;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/**
* Inventory Application starts container (Spring Boot) and exposes the Inventory micro-service.
*/
@SpringBootApplication
public class InventoryApplication {
public static void main(String[] args) {
SpringApplication.run(InventoryApplication.class, args);
}
}

42
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.inventory.microservice;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class InventoryController {
/**
* Endpoint to retrieve a product's inventories.
*
* @return product inventory.
*/
@RequestMapping(value = "/inventories", method = RequestMethod.GET)
public int getProductInventories() {
return 5;
}
}

24
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#
# The MIT License
# Copyright (c) 2014 Ilkka Seppälä
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
server.port=51516

38
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
* <p/>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p/>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p/>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.inventory.microservice;
import org.junit.Assert;
import org.junit.Test;
public class InventoryControllerTest {
@Test
public void testGetProductInventories() throws Exception {
InventoryController inventoryController = new InventoryController();
int numberOfInventories = inventoryController.getProductInventories();
Assert.assertEquals(5, numberOfInventories);
}
}

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<?xml version="1.0" encoding="UTF-8"?>
<!--
The MIT License
Copyright (c) 2014 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.13.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>aggregator-microservices</artifactId>
<packaging>pom</packaging>
<modules>
<module>information-microservice</module>
<module>aggregator-service</module>
<module>inventory-microservice</module>
</modules>
</project>

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---
layout: pattern
title: API Gateway
folder: api-gateway
permalink: /patterns/api-gateway/
categories: Architectural
tags:
- Java
- Difficulty-Intermediate
- Spring
---
## Intent
Aggregate calls to microservices in a single location: the API Gateway. The user makes a single
call to the API Gateway, and the API Gateway then calls each relevant microservice.
![alt text](./etc/api-gateway.png "API Gateway")
## Applicability
Use the API Gateway pattern when
* you're also using the Microservices pattern and need a single point of aggregation for your
microservice calls
## Credits
* [microservices.io - API Gateway](http://microservices.io/patterns/apigateway.html)
* [NGINX - Building Microservices: Using an API Gateway](https://www.nginx.com/blog/building-microservices-using-an-api-gateway/)

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<?xml version="1.0" encoding="UTF-8"?>
<!--
The MIT License
Copyright (c) 2014 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>api-gateway</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.13.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>api-gateway-service</artifactId>
<packaging>jar</packaging>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-core</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>${spring-boot.version}</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>

64
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.api.gateway;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.annotation.Resource;
/**
* The ApiGateway aggregates calls to microservices based on the needs of the individual clients.
*/
@RestController
public class ApiGateway {
@Resource
private ImageClient imageClient;
@Resource
private PriceClient priceClient;
/**
* Retrieves product information that desktop clients need
* @return Product information for clients on a desktop
*/
@RequestMapping("/desktop")
public DesktopProduct getProductDesktop() {
DesktopProduct desktopProduct = new DesktopProduct();
desktopProduct.setImagePath(imageClient.getImagePath());
desktopProduct.setPrice(priceClient.getPrice());
return desktopProduct;
}
/**
* Retrieves product information that mobile clients need
* @return Product information for clients on a mobile device
*/
@RequestMapping("/mobile")
public MobileProduct getProductMobile() {
MobileProduct mobileProduct = new MobileProduct();
mobileProduct.setPrice(priceClient.getPrice());
return mobileProduct;
}
}

66
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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.api.gateway;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/**
* With the Microservices pattern, a client may need data from multiple different microservices.
* If the client called each microservice directly, that could contribute to longer load times,
* since the client would have to make a network request for each microservice called. Moreover,
* having the client call each microservice directly ties the client to that microservice - if the
* internal implementations of the microservices change (for example, if two microservices are
* combined sometime in the future) or if the location (host and port) of a microservice changes,
* then every client that makes use of those microservices must be updated.
*
* <p>
* The intent of the API Gateway pattern is to alleviate some of these issues. In the API Gateway
* pattern, an additional entity (the API Gateway) is placed between the client and the
* microservices. The job of the API Gateway is to aggregate the calls to the microservices.
* Rather than the client calling each microservice individually, the client calls the API Gateway
* a single time. The API Gateway then calls each of the microservices that the client needs.
*
* <p>
* This implementation shows what the API Gateway pattern could look like for an e-commerce site.
* The {@link ApiGateway} makes calls to the Image and Price microservices using the
* {@link ImageClientImpl} and {@link PriceClientImpl} respectively. Customers viewing the site on a
* desktop device can see both price information and an image of a product, so the {@link ApiGateway}
* calls both of the microservices and aggregates the data in the {@link DesktopProduct} model.
* However, mobile users only see price information; they do not see a product image. For mobile
* users, the {@link ApiGateway} only retrieves price information, which it uses to populate the
* {@link MobileProduct}.
*/
@SpringBootApplication
public class App {
/**
* Program entry point
*
* @param args
* command line args
*/
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.api.gateway;
/**
* Encapsulates all of the information that a desktop client needs to display a product.
*/
public class DesktopProduct {
/**
* The price of the product
*/
private String price;
/**
* The path to the image of the product
*/
private String imagePath;
public String getPrice() {
return price;
}
public void setPrice(String price) {
this.price = price;
}
public String getImagePath() {
return imagePath;
}
public void setImagePath(String imagePath) {
this.imagePath = imagePath;
}
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.api.gateway;
/**
* An interface used to communicate with the Image microservice
*/
public interface ImageClient {
String getImagePath();
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.api.gateway;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.springframework.stereotype.Component;
import java.io.IOException;
/**
* An adapter to communicate with the Image microservice
*/
@Component
public class ImageClientImpl implements ImageClient{
/**
* Makes a simple HTTP Get request to the Image microservice
* @return The path to the image
*/
@Override
public String getImagePath() {
String response = null;
try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
HttpGet httpGet = new HttpGet("http://localhost:50005/image-path");
try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
response = EntityUtils.toString(httpResponse.getEntity());
}
} catch (IOException e) {
e.printStackTrace();
}
return response;
}
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.api.gateway;
/**
* Encapsulates all of the information that mobile client needs to display a product.
*/
public class MobileProduct {
/**
* The price of the product
*/
private String price;
public String getPrice() {
return price;
}
public void setPrice(String price) {
this.price = price;
}
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.api.gateway;
/**
* An interface used to communicate with the Price microservice
*/
public interface PriceClient {
String getPrice();
}

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.api.gateway;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.springframework.stereotype.Component;
import java.io.IOException;
/**
* An adapter to communicate with the Price microservice
*/
@Component
public class PriceClientImpl implements PriceClient{
/**
* Makes a simple HTTP Get request to the Price microservice
* @return The price of the product
*/
@Override
public String getPrice() {
String response = null;
try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
HttpGet httpGet = new HttpGet("http://localhost:50006/price");
try (CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
response = EntityUtils.toString(httpResponse.getEntity());
}
} catch (IOException e) {
e.printStackTrace();
}
return response;
}
}

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#
# The MIT License
# Copyright (c) 2014 Ilkka Seppälä
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
server.port=50004

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.api.gateway;
import org.junit.Before;
import org.junit.Test;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.when;
public class ApiGatewayTest {
@InjectMocks
private ApiGateway apiGateway;
@Mock
private ImageClient imageClient;
@Mock
private PriceClient priceClient;
@Before
public void setup() {
MockitoAnnotations.initMocks(this);
}
/**
* Tests getting the data for a desktop client
*/
@Test
public void testGetProductDesktop() {
String imagePath = "/product-image.png";
String price = "20";
when(imageClient.getImagePath()).thenReturn(imagePath);
when(priceClient.getPrice()).thenReturn(price);
DesktopProduct desktopProduct = apiGateway.getProductDesktop();
assertEquals(price, desktopProduct.getPrice());
assertEquals(imagePath, desktopProduct.getImagePath());
}
/**
* Tests getting the data for a mobile client
*/
@Test
public void testGetProductMobile() {
String price = "20";
when(priceClient.getPrice()).thenReturn(price);
MobileProduct mobileProduct = apiGateway.getProductMobile();
assertEquals(price, mobileProduct.getPrice());
}
}

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<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.1.9" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
realizations="true" associations="true" dependencies="false" nesting-relationships="true" router="FAN">
<class id="1" language="java" name="com.iluwatar.api.gateway.ApiGateway" project="api-gateway"
file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ApiGateway.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="125" y="87"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="2" language="java" name="com.iluwatar.api.gateway.DesktopProduct" project="api-gateway"
file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/DesktopProduct.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="388" y="109"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<interface id="3" language="java" name="com.iluwatar.api.gateway.ImageClient" project="api-gateway"
file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ImageClient.java" binary="false" corner="BOTTOM_RIGHT">
<position height="81" width="129" x="13" y="197"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</interface>
<class id="4" language="java" name="com.iluwatar.api.gateway.ImageClientImpl" project="api-gateway"
file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ImageClientImpl.java" binary="false" corner="BOTTOM_RIGHT">
<position height="99" width="129" x="13" y="325"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="5" language="java" name="com.iluwatar.api.gateway.MobileProduct" project="api-gateway"
file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/MobileProduct.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="376" y="293"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<interface id="6" language="java" name="com.iluwatar.api.gateway.PriceClient" project="api-gateway"
file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/PriceClient.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="222" y="231"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</interface>
<class id="7" language="java" name="com.iluwatar.api.gateway.PriceClientImpl" project="api-gateway"
file="/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/PriceClientImpl.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="223" y="374"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<association id="8">
<end type="SOURCE" refId="1" navigable="false">
<attribute id="9" name="imageClient"/>
<multiplicity id="10" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="3" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<realization id="11">
<end type="SOURCE" refId="4"/>
<end type="TARGET" refId="3"/>
</realization>
<association id="12">
<end type="SOURCE" refId="1" navigable="false">
<attribute id="13" name="priceClient"/>
<multiplicity id="14" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="6" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<realization id="15">
<end type="SOURCE" refId="7"/>
<end type="TARGET" refId="6"/>
</realization>
<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</classifier-display>
<association-display labels="true" multiplicity="true"/>
</class-diagram>

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<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.1.9" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
realizations="true" associations="true" dependencies="false" nesting-relationships="true" router="FAN">
<class id="1" language="java" name="com.iluwatar.image.microservice.ImageController" project="image-microservice"
file="/image-microservice/src/main/java/com/iluwatar/image/microservice/ImageController.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="87" y="61"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</classifier-display>
<association-display labels="true" multiplicity="true"/>
</class-diagram>

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<?xml version="1.0" encoding="UTF-8"?>
<!--
The MIT License
Copyright (c) 2014 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>api-gateway</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.13.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>image-microservice</artifactId>
<packaging>jar</packaging>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>${spring-boot.version}</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>

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/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.image.microservice;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/**
* ImageApplication starts up Spring Boot, exposing endpoints for the Image microservice through
* the {@link ImageController}.
*/
@SpringBootApplication
public class ImageApplication {
/**
* Microservice entry point
* @param args
* command line args
*/
public static void main(String[] args) {
SpringApplication.run(ImageApplication.class, args);
}
}

43
api-gateway/image-microservice/src/main/java/com/iluwatar/image/microservice/ImageController.java Normal file
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@ -0,0 +1,43 @@
/**
* The MIT License
* Copyright (c) 2014 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.image.microservice;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
/**
* Exposes the Image microservice's endpoints
*/
@RestController
public class ImageController {
/**
* An endpoint for a user to retrieve an image path
* @return An image path
*/
@RequestMapping(value = "/image-path", method = RequestMethod.GET)
public String getImagePath() {
return "/product-image.png";
}
}

24
api-gateway/image-microservice/src/main/resources/application.properties Normal file
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#
# The MIT License
# Copyright (c) 2014 Ilkka Seppälä
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
server.port=50005

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