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# Code Coverage Report generation
To generate the code coverage report, execute the following command:
> mvn clean verify jacoco:report
> 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

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@ -8,6 +8,7 @@
[![License MIT](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/iluwatar/java-design-patterns/master/LICENSE.md)
[![Join the chat at https://gitter.im/iluwatar/java-design-patterns](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
[![Quality Gate](https://sonarcloud.io/api/project_badges/measure?project=com.iluwatar%3Ajava-design-patterns&metric=alert_status)](https://sonarcloud.io/dashboard/index/com.iluwatar%3Ajava-design-patterns)
[![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/1503/badge)](https://bestpractices.coreinfrastructure.org/projects/1503)
# Introduction

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<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>abstract-document</artifactId>
<dependencies>

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@ -34,7 +34,7 @@ Wikipedia says
Translating the kingdom example above. First of all we have some interfaces and implementation for the objects in the kingdom
```java
```
public interface Castle {
String getDescription();
}
@ -74,7 +74,7 @@ public class ElfArmy implements Army {
Then we have the abstraction and implementations for the kingdom factory
```java
```
public interface KingdomFactory {
Castle createCastle();
King createKing();
@ -108,7 +108,7 @@ public class OrcKingdomFactory implements KingdomFactory {
Now we have our abstract factory that lets us make family of related objects i.e. Elven kingdom factory creates Elven castle, king and army etc.
```java
```
KingdomFactory factory = new ElfKingdomFactory();
Castle castle = factory.createCastle();
King king = factory.createKing();
@ -123,7 +123,7 @@ Now, we can design a factory for our different kingdom factories. In this exampl
The client can use FactoryMaker to create the desired concrete factory which, in turn, will produce different concrete objects (Army, King, Castle).
In this example, we also used an enum to parameterize which type of kingdom factory the client will ask for.
```java
```
public static class FactoryMaker {
public enum KingdomType {

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<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>abstract-factory</artifactId>
<dependencies>

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@ -1,39 +0,0 @@
---
layout: pattern
title: Acyclic Visitor
folder: acyclic-visitor
permalink: /patterns/acyclic-visitor/
categories: Behavioral
tags:
- Java
- Difficulty-Intermediate
---
![alt text](./etc/acyclic-visitor.png "Acyclic Visitor")
## Intent
Allow new functions to be added to existing class hierarchies without affecting those hierarchies, and without creating the troublesome dependency cycles that are inherent to the GOF VISITOR Pattern.
## Applicability
This pattern can be used:
* When you need to add a new function to an existing hierarchy without the need to alter or affect that hierarchy.
* When there are functions that operate upon a hierarchy, but which do not belong in the hierarchy itself. e.g. the ConfigureForDOS / ConfigureForUnix / ConfigureForX issue.
* When you need to perform very different operations on an object depending upon its type.
* When the visited class hierarchy will be frequently extended with new derivatives of the Element class.
* When the recompilation, relinking, retesting or redistribution of the derivatives of Element is very expensive.
## Consequences
The good:
* No dependency cycles between class hierarchies.
* No need to recompile all the visitors if a new one is added.
* Does not cause compilation failure in existing visitors if class hierarchy has a new member.
The bad:
* Violates the principle of least surprise or Liskov's Substitution principle by showing that it can accept all visitors but actually only being interested in particular visitors.
* Parallel hierarchy of visitors has to be created for all members in visitable class hierarchy.
## Related patterns
* [Visitor Pattern](../visitor/README.md)
## Credits
* [Acyclic Visitor](http://condor.depaul.edu/dmumaugh/OOT/Design-Principles/acv.pdf)

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<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.2.2" icons="true" 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.acyclicvisitor.ModemVisitor" project="acyclic-visitor"
file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ModemVisitor.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="860" y="67"/>
<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="2" language="java" name="com.iluwatar.acyclicvisitor.Modem" project="acyclic-visitor"
file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Modem.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="327" y="77"/>
<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.acyclicvisitor.ConfigureForUnixVisitor" project="acyclic-visitor"
file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForUnixVisitor.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="124" width="196" x="647" y="225"/>
<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.acyclicvisitor.Zoom" project="acyclic-visitor"
file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Zoom.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="203" y="305"/>
<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="5" language="java" name="com.iluwatar.acyclicvisitor.HayesVisitor" project="acyclic-visitor"
file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/HayesVisitor.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="1019" y="468"/>
<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>
<interface id="6" language="java" name="com.iluwatar.acyclicvisitor.ZoomVisitor" project="acyclic-visitor"
file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ZoomVisitor.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="758" y="467"/>
<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.acyclicvisitor.Hayes" project="acyclic-visitor"
file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Hayes.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="479" y="307"/>
<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="8" language="java" name="com.iluwatar.acyclicvisitor.ConfigureForDosVisitor" project="acyclic-visitor"
file="/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForDosVisitor.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="142" width="192" x="883" y="225"/>
<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>
<generalization id="9">
<end type="SOURCE" refId="7"/>
<end type="TARGET" refId="2"/>
</generalization>
<realization id="10">
<end type="SOURCE" refId="8"/>
<end type="TARGET" refId="6"/>
</realization>
<realization id="11">
<end type="SOURCE" refId="8"/>
<end type="TARGET" refId="5"/>
</realization>
<realization id="12">
<end type="SOURCE" refId="3"/>
<end type="TARGET" refId="6"/>
</realization>
<realization id="13">
<end type="SOURCE" refId="3"/>
<end type="TARGET" refId="1"/>
</realization>
<realization id="14">
<end type="SOURCE" refId="8"/>
<end type="TARGET" refId="1"/>
</realization>
<generalization id="15">
<end type="SOURCE" refId="4"/>
<end type="TARGET" refId="2"/>
</generalization>
<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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<!--
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>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
</parent>
<artifactId>acyclic-visitor</artifactId>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
<!-- https://mvnrepository.com/artifact/org.assertj/assertj-core -->
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>3.9.1</version>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/uk.org.lidalia/slf4j-test -->
<dependency>
<groupId>uk.org.lidalia</groupId>
<artifactId>slf4j-test</artifactId>
<version>1.0.0</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-api</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-engine</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-all</artifactId>
<version>1.9.5</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>

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/**
* The MIT License
* 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
* 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.acyclicvisitor;
/**
* All ModemVisitor interface extends all visitor interfaces. This interface
* provides ease of use when a visitor needs to visit all modem types.
*/
public interface AllModemVisitor extends ZoomVisitor, HayesVisitor{
}

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/**
* The MIT License
* 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
* 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.acyclicvisitor;
/**
* The Acyclic Visitor pattern allows new functions to be added to existing class
* hierarchies without affecting those hierarchies, and without creating the dependency
* cycles that are inherent to the GoF Visitor pattern, by making the Visitor base class
* degenerate
* <p>
* In this example the visitor base class is {@link ModemVisitor}. The base class of the
* visited hierarchy is {@link Modem} and has two children {@link Hayes} and {@link Zoom}
* each one having its own visitor interface {@link HayesVisitor} and {@link ZoomVisitor}
* respectively. {@link ConfigureForUnixVisitor} and {@link ConfigureForDosVisitor}
* implement each derivative's visit method only if it is required
*/
public class App {
/**
* Program's entry point
*/
public static void main(String[] args) {
ConfigureForUnixVisitor conUnix = new ConfigureForUnixVisitor();
ConfigureForDosVisitor conDos = new ConfigureForDosVisitor();
Zoom zoom = new Zoom();
Hayes hayes = new Hayes();
hayes.accept(conDos); // Hayes modem with Unix configurator
zoom.accept(conDos); // Zoom modem with Dos configurator
hayes.accept(conUnix); // Hayes modem with Unix configurator
zoom.accept(conUnix); // Zoom modem with Unix configurator
}
}

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/**
* The MIT License
* 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
* 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.acyclicvisitor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* ConfigureForDosVisitor class implements both zoom's and hayes' visit method
* for Dos manufacturer
*/
public class ConfigureForDosVisitor implements AllModemVisitor {
private static final Logger LOGGER = LoggerFactory.getLogger(ConfigureForDosVisitor.class);
public void visit(Hayes hayes) {
LOGGER.info(hayes + " used with Dos configurator.");
}
public void visit(Zoom zoom) {
LOGGER.info(zoom + " used with Dos configurator.");
}
}

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@ -1,40 +0,0 @@
/**
* The MIT License
* 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
* 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.acyclicvisitor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* ConfigureForUnixVisitor class implements zoom's visit method for Unix
* manufacturer, unlike traditional visitor pattern, this class may selectively implement
* visit for other modems.
*/
public class ConfigureForUnixVisitor implements ZoomVisitor {
private static final Logger LOGGER = LoggerFactory.getLogger(ConfigureForUnixVisitor.class);
public void visit(Zoom zoom) {
LOGGER.info(zoom + " used with Unix configurator.");
}
}

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/**
* The MIT License
* 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
* 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.acyclicvisitor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Hayes class implements its accept method
*/
public class Hayes extends Modem {
private static final Logger LOGGER = LoggerFactory.getLogger(ConfigureForDosVisitor.class);
/**
* Accepts all visitors but honors only HayesVisitor
*/
@Override
public void accept(ModemVisitor modemVisitor) {
if (modemVisitor instanceof HayesVisitor) {
((HayesVisitor) modemVisitor).visit(this);
} else {
LOGGER.info("Only HayesVisitor is allowed to visit Hayes modem");
}
}
/**
* Hayes' modem's toString
* method
*/
@Override
public String toString() {
return "Hayes modem";
}
}

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/**
* The MIT License
* 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
* 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.acyclicvisitor;
/**
* HayesVisitor interface
*/
public interface HayesVisitor extends ModemVisitor {
void visit(Hayes hayes);
}

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/**
* The MIT License
* 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
* 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.acyclicvisitor;
/**
* Modem abstract class
*/
public abstract class Modem {
public abstract void accept(ModemVisitor modemVisitor);
}

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/**
* The MIT License
* 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
* 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.acyclicvisitor;
/**
* ModemVisitor interface does not contain any visit methods so that it does not
* depend on the visited hierarchy. Each derivative's visit method is declared in
* its own visitor interface
*/
public interface ModemVisitor {
// Visitor is a degenerate base class for all visitors.
}

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/**
* The MIT License
* 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
* 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.acyclicvisitor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Zoom class implements its accept method
*/
public class Zoom extends Modem {
private static final Logger LOGGER = LoggerFactory.getLogger(ConfigureForDosVisitor.class);
/**
* Accepts all visitors but honors only ZoomVisitor
*/
@Override
public void accept(ModemVisitor modemVisitor) {
if (modemVisitor instanceof ZoomVisitor) {
((ZoomVisitor) modemVisitor).visit(this);
} else {
LOGGER.info("Only ZoomVisitor is allowed to visit Zoom modem");
}
}
/**
* Zoom modem's toString
* method
*/
@Override
public String toString() {
return "Zoom modem";
}
}

View File

@ -1,39 +0,0 @@
/**
* The MIT License
* 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
* 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.acyclicvisitor;
import org.junit.jupiter.api.Test;
import com.iluwatar.acyclicvisitor.App;
/**
* Tests that the Acyclic Visitor example runs without errors.
*/
public class AppTest {
@Test
public void test() {
String[] args = {};
App.main(args);
}
}

View File

@ -1,75 +0,0 @@
/**
* The MIT License
* 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
* 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.acyclicvisitor;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.groups.Tuple.tuple;
import static org.mockito.Mockito.mock;
import static uk.org.lidalia.slf4jext.Level.INFO;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.Test;
import com.iluwatar.acyclicvisitor.ConfigureForDosVisitor;
import com.iluwatar.acyclicvisitor.Hayes;
import com.iluwatar.acyclicvisitor.HayesVisitor;
import com.iluwatar.acyclicvisitor.Zoom;
import com.iluwatar.acyclicvisitor.ZoomVisitor;
import uk.org.lidalia.slf4jtest.TestLogger;
import uk.org.lidalia.slf4jtest.TestLoggerFactory;
/**
* ConfigureForDosVisitor test class
*/
public class ConfigureForDosVisitorTest {
TestLogger logger = TestLoggerFactory.getTestLogger(ConfigureForDosVisitor.class);
@Test
public void testVisitForZoom() {
ConfigureForDosVisitor conDos = new ConfigureForDosVisitor();
Zoom zoom = new Zoom();
conDos.visit(zoom);
assertThat(logger.getLoggingEvents()).extracting("level", "message").contains(
tuple(INFO, zoom + " used with Dos configurator."));
}
@Test
public void testVisitForHayes() {
ConfigureForDosVisitor conDos = new ConfigureForDosVisitor();
Hayes hayes = new Hayes();
conDos.visit(hayes);
assertThat(logger.getLoggingEvents()).extracting("level", "message").contains(
tuple(INFO, hayes + " used with Dos configurator."));
}
@AfterEach
public void clearLoggers() {
TestLoggerFactory.clear();
}
}

View File

@ -1,65 +0,0 @@
/**
* The MIT License
* 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
* 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.acyclicvisitor;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.groups.Tuple.tuple;
import static uk.org.lidalia.slf4jext.Level.INFO;
import static org.mockito.Mockito.mock;
import uk.org.lidalia.slf4jtest.TestLogger;
import uk.org.lidalia.slf4jtest.TestLoggerFactory;
import org.junit.jupiter.api.Test;
import com.iluwatar.acyclicvisitor.ConfigureForUnixVisitor;
import com.iluwatar.acyclicvisitor.Hayes;
import com.iluwatar.acyclicvisitor.HayesVisitor;
import com.iluwatar.acyclicvisitor.Zoom;
import com.iluwatar.acyclicvisitor.ZoomVisitor;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.Assertions;
/**
* ConfigureForUnixVisitor test class
*/
public class ConfigureForUnixVisitorTest {
TestLogger logger = TestLoggerFactory.getTestLogger(ConfigureForUnixVisitor.class);
@AfterEach
public void clearLoggers() {
TestLoggerFactory.clear();
}
@Test
public void testVisitForZoom() {
ConfigureForUnixVisitor conUnix = new ConfigureForUnixVisitor();
Zoom zoom = new Zoom();
conUnix.visit(zoom);
assertThat(logger.getLoggingEvents()).extracting("level", "message").contains(
tuple(INFO, zoom + " used with Unix configurator."));
}
}

View File

@ -1,60 +0,0 @@
/**
* The MIT License
* 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
* 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.acyclicvisitor;
import static org.mockito.Matchers.eq;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.verifyZeroInteractions;
import org.junit.jupiter.api.Test;
import com.iluwatar.acyclicvisitor.ConfigureForDosVisitor;
import com.iluwatar.acyclicvisitor.ConfigureForUnixVisitor;
import com.iluwatar.acyclicvisitor.Hayes;
import com.iluwatar.acyclicvisitor.HayesVisitor;
/**
* Hayes test class
*/
public class HayesTest {
@Test
public void testAcceptForDos() {
Hayes hayes = new Hayes();
ConfigureForDosVisitor mockVisitor = mock(ConfigureForDosVisitor.class);
hayes.accept(mockVisitor);
verify((HayesVisitor)mockVisitor).visit(eq(hayes));
}
@Test
public void testAcceptForUnix() {
Hayes hayes = new Hayes();
ConfigureForUnixVisitor mockVisitor = mock(ConfigureForUnixVisitor.class);
hayes.accept(mockVisitor);
verifyZeroInteractions(mockVisitor);
}
}

View File

@ -1,59 +0,0 @@
/**
* The MIT License
* 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
* 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.acyclicvisitor;
import static org.mockito.Matchers.eq;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.mock;
import org.junit.jupiter.api.Test;
import com.iluwatar.acyclicvisitor.ConfigureForDosVisitor;
import com.iluwatar.acyclicvisitor.ConfigureForUnixVisitor;
import com.iluwatar.acyclicvisitor.Zoom;
import com.iluwatar.acyclicvisitor.ZoomVisitor;
/**
* Zoom test class
*/
public class ZoomTest {
@Test
public void testAcceptForDos() {
Zoom zoom = new Zoom();
ConfigureForDosVisitor mockVisitor = mock(ConfigureForDosVisitor.class);
zoom.accept(mockVisitor);
verify((ZoomVisitor)mockVisitor).visit(eq(zoom));
}
@Test
public void testAcceptForUnix() {
Zoom zoom = new Zoom();
ConfigureForUnixVisitor mockVisitor = mock(ConfigureForUnixVisitor.class);
zoom.accept(mockVisitor);
verify((ZoomVisitor)mockVisitor).visit(eq(zoom));
}
}

View File

@ -40,7 +40,7 @@ Consider a captain that can only use rowing boats and cannot sail at all.
First we have interfaces `RowingBoat` and `FishingBoat`
```java
```
public interface RowingBoat {
void row();
}
@ -55,7 +55,7 @@ public class FishingBoat {
And captain expects an implementation of `RowingBoat` interface to be able to move
```java
```
public class Captain implements RowingBoat {
private RowingBoat rowingBoat;
@ -73,7 +73,7 @@ public class Captain implements RowingBoat {
Now let's say the pirates are coming and our captain needs to escape but there is only fishing boat available. We need to create an adapter that allows the captain to operate the fishing boat with his rowing boat skills.
```java
```
public class FishingBoatAdapter implements RowingBoat {
private static final Logger LOGGER = LoggerFactory.getLogger(FishingBoatAdapter.class);
@ -93,7 +93,7 @@ public class FishingBoatAdapter implements RowingBoat {
And now the `Captain` can use the `FishingBoat` to escape the pirates.
```java
```
Captain captain = new Captain(new FishingBoatAdapter());
captain.row();
```

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>adapter</artifactId>
<dependencies>

View File

@ -29,7 +29,7 @@
<parent>
<artifactId>aggregator-microservices</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

View File

@ -29,7 +29,7 @@
<parent>
<artifactId>aggregator-microservices</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

View File

@ -29,7 +29,7 @@
<parent>
<artifactId>aggregator-microservices</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

View File

@ -29,7 +29,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>aggregator-microservices</artifactId>

View File

@ -1,178 +0,0 @@
---
layout: pattern
title: Ambassador
folder: ambassador
permalink: /patterns/ambassador/
categories: Structural
tags:
- Java
- Difficulty-Intermediate
---
## Intent
Provide a helper service instance on a client and offload common functionality away from a shared resource.
## Explanation
Real world example
> A remote service has many clients accessing a function it provides. The service is a legacy application and is impossible to update. Large numbers of requests from users are causing connectivity issues. New rules for request frequency should be implemented along with latency checks and client-side logging.
In plain words
> Using the ambassador pattern, we can implement less-frequent polling from clients along with latency checks and logging.
Microsoft documentation states
> An ambassador service can be thought of as an out-of-process proxy that is co-located with the client.
This pattern can be useful for offloading common client connectivity tasks such as monitoring, logging, routing, security (such as TLS), and resiliency patterns in a language agnostic way. It is often used with legacy applications, or other applications that are difficult to modify, in order to extend their networking capabilities. It can also enable a specialized team to implement those features.
**Programmatic Example**
With the above example in mind we will imitate the functionality in a simple manner. We have an interface implemented by the remote service as well as the ambassador service:
```java
interface RemoteServiceInterface {
long doRemoteFunction(int value) throws Exception;
}
```
A remote services represented as a singleton.
```java
public class RemoteService implements RemoteServiceInterface {
private static final Logger LOGGER = LoggerFactory.getLogger(RemoteService.class);
private static RemoteService service = null;2
static synchronized RemoteService getRemoteService() {
if (service == null) {
service = new RemoteService();
}
return service;
}
private RemoteService() {}
@Override
public long doRemoteFunction(int value) {
long waitTime = (long) Math.floor(Math.random() * 1000);
try {
sleep(waitTime);
} catch (InterruptedException e) {
LOGGER.error("Thread sleep interrupted", e)
}
return waitTime >= 200 ? value * 10 : -1;
}
}
```
A service ambassador adding additional features such as logging, latency checks
```java
public class ServiceAmbassador implements RemoteServiceInterface {
private static final Logger LOGGER = LoggerFactory.getLogger(ServiceAmbassador.class);
private static final int RETRIES = 3;
private static final int DELAY_MS = 3000;
ServiceAmbassador() {}
@Override
public long doRemoteFunction(int value) {
return safeCall(value);
}
private long checkLatency(int value) {
RemoteService service = RemoteService.getRemoteService();
long startTime = System.currentTimeMillis();
long result = service.doRemoteFunction(value);
long timeTaken = System.currentTimeMillis() - startTime;
LOGGER.info("Time taken (ms): " + timeTaken);
return result;
}
private long safeCall(int value) {
int retries = 0;
long result = -1;
for (int i = 0; i < RETRIES; i++) {
if (retries >= RETRIES) {
return -1;
}
if ((result = checkLatency(value)) == -1) {
LOGGER.info("Failed to reach remote: (" + (i + 1) + ")");
retries++;
try {
sleep(DELAY_MS);
} catch (InterruptedException e) {
LOGGER.error("Thread sleep state interrupted", e);
}
} else {
break;
}
}
return result;
}
}
```
A client has a local service ambassador used to interact with the remote service:
```java
public class Client {
private ServiceAmbassador serviceAmbassador;
Client() {
serviceAmbassador = new ServiceAmbassador();
}
long useService(int value) {
long result = serviceAmbassador.doRemoteFunction(value);
LOGGER.info("Service result: " + result)
return result;
}
}
```
And here are two clients using the service.
```java
Client host1 = new Client();
Client host2 = new Client();
host1.useService(12);
host2.useService(73);
```
## Applicability
Ambassador is applicable when working with a legacy remote service that cannot
be modified or would be extremely difficult to modify. Connectivity features can
be implemented on the client avoiding the need for changes on the remote service.
* Ambassador provides a local interface for a remote service.
* Ambassador provides logging, circuit breaking, retries and security on the client.
## Typical Use Case
* Control access to another object
* Implement logging
* Implement circuit breaking
* Offload remote service tasks
* Facilitate network connection
## Real world examples
* [Kubernetes-native API gateway for microservices](https://github.com/datawire/ambassador)
## Credits
* [Ambassador pattern](https://docs.microsoft.com/en-us/azure/architecture/patterns/ambassador)
* [Designing Distributed Systems: Patterns and Paradigms for Scalable, Reliable Services](https://books.google.co.uk/books?id=6BJNDwAAQBAJ&pg=PT35&lpg=PT35&dq=ambassador+pattern+in+real+world&source=bl&ots=d2e7GhYdHi&sig=Lfl_MDnCgn6lUcjzOg4GXrN13bQ&hl=en&sa=X&ved=0ahUKEwjk9L_18rrbAhVpKcAKHX_KA7EQ6AEIWTAI#v=onepage&q=ambassador%20pattern%20in%20real%20world&f=false)

View File

@ -1,48 +0,0 @@
<?xml version="1.0" encoding="UTF-8"?>
<!--
The MIT License
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
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>1.21.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>ambassador</artifactId>
<dependencies>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-api</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-engine</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>

View File

@ -1,53 +0,0 @@
/**
* The MIT License
* 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
* 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.ambassador;
/**
*
* The ambassador pattern creates a helper service that sends network requests on behalf of a
* client. It is often used in cloud-based applications to offload features of a remote service.
*
* An ambassador service can be thought of as an out-of-process proxy that is co-located with
* the client. Similar to the proxy design pattern, the ambassador service provides an interface
* for another remote service. In addition to the interface, the ambassador provides extra
* functionality and features, specifically offloaded common connectivity tasks. This usually
* consists of monitoring, logging, routing, security etc. This is extremely useful in
* legacy applications where the codebase is difficult to modify and allows for improvements
* in the application's networking capabilities.
*
* In this example, we will the ({@link ServiceAmbassador}) class represents the ambassador while the
* ({@link RemoteService}) class represents a remote application.
*
*/
public class App {
/**
* Entry point
*/
public static void main(String[] args) {
Client host1 = new Client();
Client host2 = new Client();
host1.useService(12);
host2.useService(73);
}
}

View File

@ -1,42 +0,0 @@
/**
* The MIT License
* 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
* 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.ambassador;
import org.slf4j.LoggerFactory;
import org.slf4j.Logger;
/**
* A simple Client
*/
public class Client {
private static final Logger LOGGER = LoggerFactory.getLogger(Client.class);
private final ServiceAmbassador serviceAmbassador = new ServiceAmbassador();
long useService(int value) {
long result = serviceAmbassador.doRemoteFunction(value);
LOGGER.info("Service result: " + result);
return result;
}
}

View File

@ -1,65 +0,0 @@
/**
* The MIT License
* 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
* 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.ambassador;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import static java.lang.Thread.sleep;
/**
* A remote legacy application represented by a Singleton implementation.
*/
public class RemoteService implements RemoteServiceInterface {
private static final Logger LOGGER = LoggerFactory.getLogger(RemoteService.class);
private static RemoteService service = null;
static synchronized RemoteService getRemoteService() {
if (service == null) {
service = new RemoteService();
}
return service;
}
private RemoteService() {}
/**
* Remote function takes a value and multiplies it by 10 taking a random amount of time.
* Will sometimes return -1. This imitates connectivity issues a client might have to account for.
* @param value integer value to be multiplied.
* @return if waitTime is more than 200ms, it returns value * 10, otherwise -1.
*/
@Override
public long doRemoteFunction(int value) {
long waitTime = (long) Math.floor(Math.random() * 1000);
try {
sleep(waitTime);
} catch (InterruptedException e) {
LOGGER.error("Thread sleep state interrupted", e);
}
return waitTime >= 200 ? value * 10 : -1;
}
}

View File

@ -1,31 +0,0 @@
/**
* The MIT License
* 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
* 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.ambassador;
/**
* Interface shared by ({@link RemoteService}) and ({@link ServiceAmbassador}).
*/
interface RemoteServiceInterface {
long doRemoteFunction(int value) throws Exception;
}

View File

@ -1,84 +0,0 @@
/**
* The MIT License
* 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
* 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.ambassador;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import static java.lang.Thread.sleep;
/**
*
* ServiceAmbassador provides an interface for a ({@link Client}) to access ({@link RemoteService}).
* The interface adds logging, latency testing and usage of the service in a safe way that will not
* add stress to the remote service when connectivity issues occur.
*
*/
public class ServiceAmbassador implements RemoteServiceInterface {
private static final Logger LOGGER = LoggerFactory.getLogger(ServiceAmbassador.class);
private static final int RETRIES = 3;
private static final int DELAY_MS = 3000;
ServiceAmbassador() {}
@Override
public long doRemoteFunction(int value) {
return safeCall(value);
}
private long checkLatency(int value) {
long startTime = System.currentTimeMillis();
long result = RemoteService.getRemoteService().doRemoteFunction(value);
long timeTaken = System.currentTimeMillis() - startTime;
LOGGER.info("Time taken (ms): " + timeTaken);
return result;
}
private long safeCall(int value) {
int retries = 0;
long result = -1;
for (int i = 0; i < RETRIES; i++) {
if (retries >= RETRIES) {
return -1;
}
if ((result = checkLatency(value)) == -1) {
LOGGER.info("Failed to reach remote: (" + (i + 1) + ")");
retries++;
try {
sleep(DELAY_MS);
} catch (InterruptedException e) {
LOGGER.error("Thread sleep state interrupted", e);
}
} else {
break;
}
}
return result;
}
}

View File

@ -1,36 +0,0 @@
/**
* The MIT License
* 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
* 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.ambassador;
import org.junit.jupiter.api.Test;
/**
* Application test
*/
public class AppTest {
@Test
public void test() {
App.main(new String[]{});
}
}

View File

@ -1,40 +0,0 @@
/**
* The MIT License
* 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
* 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.ambassador;
import org.junit.jupiter.api.Test;
/**
* Test for {@link Client}
*/
public class ClientTest {
@Test
public void test() {
Client client = new Client();
long result = client.useService(10);
assert result == 100 || result == -1;
}
}

View File

@ -1,37 +0,0 @@
/**
* The MIT License
* 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
* 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.ambassador;
import org.junit.jupiter.api.Test;
/**
* Test for {@link RemoteService}
*/
public class RemoteServiceTest {
@Test
public void test() {
long result = RemoteService.getRemoteService().doRemoteFunction(10);
assert result == 100 || result == -1;
}
}

View File

@ -1,37 +0,0 @@
/**
* The MIT License
* 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
* 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.ambassador;
import org.junit.jupiter.api.Test;
/**
* Test for {@link ServiceAmbassador}
*/
public class ServiceAmbassadorTest {
@Test
public void test() {
long result = new ServiceAmbassador().doRemoteFunction(10);
assert result == 100 || result == -1;
}
}

View File

@ -29,7 +29,7 @@
<parent>
<artifactId>api-gateway</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>api-gateway-service</artifactId>

View File

@ -29,7 +29,7 @@
<parent>
<artifactId>api-gateway</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

View File

@ -29,7 +29,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>api-gateway</artifactId>

View File

@ -29,7 +29,7 @@
<parent>
<artifactId>api-gateway</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>async-method-invocation</artifactId>
<dependencies>

View File

@ -29,7 +29,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

View File

@ -1,10 +0,0 @@
package com.iluwatar.balking;
import java.util.concurrent.TimeUnit;
/**
* An interface to simulate delay while executing some work.
*/
public interface DelayProvider {
void executeAfterDelay(long interval, TimeUnit timeUnit, Runnable task);
}

View File

@ -25,38 +25,17 @@ package com.iluwatar.balking;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.concurrent.TimeUnit;
/**
* Washing machine class
*/
public class WashingMachine {
private static final Logger LOGGER = LoggerFactory.getLogger(WashingMachine.class);
private final DelayProvider delayProvider;
private WashingMachineState washingMachineState;
/**
* Creates a new instance of WashingMachine
*/
public WashingMachine() {
this((interval, timeUnit, task) -> {
try {
Thread.sleep(timeUnit.toMillis(interval));
} catch (InterruptedException ie) {
ie.printStackTrace();
}
task.run();
});
}
/**
* Creates a new instance of WashingMachine using provided delayProvider. This constructor is used only for
* unit testing purposes.
*/
public WashingMachine(DelayProvider delayProvider) {
this.delayProvider = delayProvider;
this.washingMachineState = WashingMachineState.ENABLED;
washingMachineState = WashingMachineState.ENABLED;
}
public WashingMachineState getWashingMachineState() {
@ -77,8 +56,12 @@ public class WashingMachine {
washingMachineState = WashingMachineState.WASHING;
}
LOGGER.info("{}: Doing the washing", Thread.currentThread().getName());
this.delayProvider.executeAfterDelay(50, TimeUnit.MILLISECONDS, this::endOfWashing);
try {
Thread.sleep(50);
} catch (InterruptedException ie) {
ie.printStackTrace();
}
endOfWashing();
}
/**

View File

@ -24,6 +24,8 @@ package com.iluwatar.balking;
import org.junit.jupiter.api.Test;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import static org.junit.jupiter.api.Assertions.assertEquals;
@ -33,39 +35,31 @@ import static org.junit.jupiter.api.Assertions.assertEquals;
*/
public class WashingMachineTest {
private FakeDelayProvider fakeDelayProvider = new FakeDelayProvider();
private volatile WashingMachineState machineStateGlobal;
@Test
public void wash() {
WashingMachine washingMachine = new WashingMachine(fakeDelayProvider);
washingMachine.wash();
washingMachine.wash();
WashingMachineState machineStateGlobal = washingMachine.getWashingMachineState();
fakeDelayProvider.task.run();
// washing machine remains in washing state
public void wash() throws Exception {
WashingMachine washingMachine = new WashingMachine();
ExecutorService executorService = Executors.newFixedThreadPool(2);
executorService.execute(washingMachine::wash);
executorService.execute(() -> {
washingMachine.wash();
machineStateGlobal = washingMachine.getWashingMachineState();
});
executorService.shutdown();
try {
executorService.awaitTermination(10, TimeUnit.SECONDS);
} catch (InterruptedException ie) {
ie.printStackTrace();
}
assertEquals(WashingMachineState.WASHING, machineStateGlobal);
// washing machine goes back to enabled state
assertEquals(WashingMachineState.ENABLED, washingMachine.getWashingMachineState());
}
@Test
public void endOfWashing() {
public void endOfWashing() throws Exception {
WashingMachine washingMachine = new WashingMachine();
washingMachine.wash();
assertEquals(WashingMachineState.ENABLED, washingMachine.getWashingMachineState());
}
private class FakeDelayProvider implements DelayProvider {
private Runnable task;
@Override
public void executeAfterDelay(long interval, TimeUnit timeUnit, Runnable task) {
this.task = task;
}
}
}

View File

@ -34,7 +34,7 @@ Wikipedia says
Translating our weapon example from above. Here we have the `Weapon` hierarchy
```java
```
public interface Weapon {
void wield();
void swing();
@ -109,7 +109,7 @@ public class Hammer implements Weapon {
And the separate enchantment hierarchy
```java
```
public interface Enchantment {
void onActivate();
void apply();
@ -155,7 +155,7 @@ public class SoulEatingEnchantment implements Enchantment {
And both the hierarchies in action
```java
```
Sword enchantedSword = new Sword(new SoulEatingEnchantment());
enchantedSword.wield();
enchantedSword.swing();

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>bridge</artifactId>
<dependencies>

View File

@ -31,7 +31,7 @@ Wikipedia says
Having said that let me add a bit about what telescoping constructor anti-pattern is. At one point or the other we have all seen a constructor like below:
```java
```
public Hero(Profession profession, String name, HairType hairType, HairColor hairColor, Armor armor, Weapon weapon) {
}
```
@ -42,7 +42,7 @@ As you can see the number of constructor parameters can quickly get out of hand
The sane alternative is to use the Builder pattern. First of all we have our hero that we want to create
```java
```
public final class Hero {
private final Profession profession;
private final String name;
@ -64,7 +64,7 @@ public final class Hero {
And then we have the builder
```java
```
public static class Builder {
private final Profession profession;
private final String name;
@ -109,7 +109,7 @@ And then we have the builder
And then it can be used as:
```java
```
Hero mage = new Hero.Builder(Profession.MAGE, "Riobard").withHairColor(HairColor.BLACK).withWeapon(Weapon.DAGGER).build();
```

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>builder</artifactId>
<dependencies>

View File

@ -30,7 +30,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>business-delegate</artifactId>
<dependencies>

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>caching</artifactId>
<dependencies>

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>callback</artifactId>
<dependencies>

View File

@ -33,7 +33,7 @@ Wikipedia says
Translating our example with orcs from above. First we have the request class
```java
```
public class Request {
private final RequestType requestType;
@ -64,7 +64,7 @@ public enum RequestType {
Then the request handler hierarchy
```java
```
public abstract class RequestHandler {
private static final Logger LOGGER = LoggerFactory.getLogger(RequestHandler.class);
private RequestHandler next;
@ -114,7 +114,7 @@ public class OrcCommander extends RequestHandler {
Then we have the Orc King who gives the orders and forms the chain
```java
```
public class OrcKing {
RequestHandler chain;
@ -134,7 +134,7 @@ public class OrcKing {
Then it is used as follows
```java
```
OrcKing king = new OrcKing();
king.makeRequest(new Request(RequestType.DEFEND_CASTLE, "defend castle")); // Orc commander handling request "defend castle"
king.makeRequest(new Request(RequestType.TORTURE_PRISONER, "torture prisoner")); // Orc officer handling request "torture prisoner"

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>chain</artifactId>
<dependencies>

View File

@ -1,30 +0,0 @@
---
layout: pattern
title: Collection Pipeline
folder: collection-pipeline
permalink: /patterns/collection-pipeline/
categories: Functional
tags:
- Java
- Difficulty-Beginner
- Functional
---
## Intent
Collection Pipeline introduces Function Composition and Collection Pipeline, two functional-style patterns that you can combine to iterate collections in your code.
In functional programming, it's common to sequence complex operations through a series of smaller modular functions or operations. The series is called a composition of functions, or a function composition. When a collection of data flows through a function composition, it becomes a collection pipeline. Function Composition and Collection Pipeline are two design patterns frequently used in functional-style programming.
![alt text](./etc/collection-pipeline.png "Collection Pipeline")
## Applicability
Use the Collection Pipeline pattern when
* When you want to perform a sequence of operations where one operation's collected output is fed into the next
* When you use a lot of statements in your code
* When you use a lot of loops in your code
## Credits
* [Function composition and the Collection Pipeline pattern](https://www.ibm.com/developerworks/library/j-java8idioms2/index.html)
* [Martin Fowler](https://martinfowler.com/articles/collection-pipeline/)
* [Java8 Streams](https://docs.oracle.com/javase/8/docs/api/java/util/stream/package-summary.html)

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@ -1,98 +0,0 @@
<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.2.2" 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.collectionpipeline.App" project="collection-pipeline"
file="/collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/App.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="150" y="100"/>
<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.collectionpipeline.ImperativeProgramming"
project="collection-pipeline"
file="/collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/ImperativeProgramming.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="437" 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>
<class id="3" language="java" name="com.iluwatar.collectionpipeline.Car" project="collection-pipeline"
file="/collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/Car.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="724" y="339"/>
<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.collectionpipeline.CarFactory" project="collection-pipeline"
file="/collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/CarFactory.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="899" y="91"/>
<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.collectionpipeline.FunctionalProgramming"
project="collection-pipeline"
file="/collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/FunctionalProgramming.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="1187" 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>
<enumeration id="6" language="java" name="com.iluwatar.collectionpipeline.Category" project="collection-pipeline"
file="/collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/Category.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="486" y="339"/>
<display autosize="true" stereotype="true" package="true" initial-value="true" 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>
</enumeration>
<class id="7" language="java" name="com.iluwatar.collectionpipeline.Person" project="collection-pipeline"
file="/collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/Person.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="723" y="91"/>
<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="7" navigable="false">
<attribute id="9" name="cars"/>
<multiplicity id="10" minimum="0" maximum="2147483647"/>
</end>
<end type="TARGET" refId="3" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<association id="11">
<end type="SOURCE" refId="3" navigable="false">
<attribute id="12" name="category"/>
<multiplicity id="13" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="6" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<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>

View File

@ -1,76 +0,0 @@
/**
* 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.
*/
package com.iluwatar.collectionpipeline;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* In imperative-style programming, it is common to use for and while loops for
* most kinds of data processing. Function composition is a simple technique
* that lets you sequence modular functions to create more complex operations.
* When you run data through the sequence, you have a collection pipeline.
* Together, the Function Composition and Collection Pipeline patterns enable
* you to create sophisticated programs where data flow from upstream to
* downstream and is passed through a series of transformations.
*
*/
public class App {
private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
/**
* Program entry point.
*
* @param args
* command line args
*/
public static void main(String[] args) {
List<Car> cars = CarFactory.createCars();
List<String> modelsImperative = ImperativeProgramming.getModelsAfter2000(cars);
LOGGER.info(modelsImperative.toString());
List<String> modelsFunctional = FunctionalProgramming.getModelsAfter2000(cars);
LOGGER.info(modelsFunctional.toString());
Map<Category, List<Car>> groupingByCategoryImperative = ImperativeProgramming.getGroupingOfCarsByCategory(cars);
LOGGER.info(groupingByCategoryImperative.toString());
Map<Category, List<Car>> groupingByCategoryFunctional = FunctionalProgramming.getGroupingOfCarsByCategory(cars);
LOGGER.info(groupingByCategoryFunctional.toString());
Person john = new Person(cars);
List<Car> sedansOwnedImperative = ImperativeProgramming.getSedanCarsOwnedSortedByDate(Arrays.asList(john));
LOGGER.info(sedansOwnedImperative.toString());
List<Car> sedansOwnedFunctional = FunctionalProgramming.getSedanCarsOwnedSortedByDate(Arrays.asList(john));
LOGGER.info(sedansOwnedFunctional.toString());
}
}

View File

@ -1,109 +0,0 @@
/**
* 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.
*/
package com.iluwatar.collectionpipeline;
/**
* A Car class that has the properties of make, model, year and category.
*/
public class Car {
private String make;
private String model;
private int year;
private Category category;
/**
* Constructor to create an instance of car.
* @param make the make of the car
* @param model the model of the car
* @param yearOfMake the year of built of the car
* @param category the {@link Category} of the car
*/
public Car(String make, String model, int yearOfMake, Category category) {
this.make = make;
this.model = model;
this.year = yearOfMake;
this.category = category;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((category == null) ? 0 : category.hashCode());
result = prime * result + ((make == null) ? 0 : make.hashCode());
result = prime * result + ((model == null) ? 0 : model.hashCode());
result = prime * result + year;
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
Car other = (Car) obj;
if (category != other.category) {
return false;
}
if (make == null) {
if (other.make != null) {
return false;
}
} else if (!make.equals(other.make)) {
return false;
}
if (model == null) {
if (other.model != null) {
return false;
}
} else if (!model.equals(other.model)) {
return false;
}
if (year != other.year) {
return false;
}
return true;
}
public String getMake() {
return make;
}
public String getModel() {
return model;
}
public int getYear() {
return year;
}
public Category getCategory() {
return category;
}
}

View File

@ -1,47 +0,0 @@
/**
* 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.
*/
package com.iluwatar.collectionpipeline;
import java.util.Arrays;
import java.util.List;
/**
* A factory class to create a collection of {@link Car} instances.
*/
public class CarFactory {
private CarFactory() {
}
/**
* Factory method to create a {@link List} of {@link Car} instances.
* @return {@link List} of {@link Car}
*/
public static List<Car> createCars() {
return Arrays.asList(new Car("Jeep", "Wrangler", 2011, Category.JEEP),
new Car("Jeep", "Comanche", 1990, Category.JEEP),
new Car("Dodge", "Avenger", 2010, Category.SEDAN),
new Car("Buick", "Cascada", 2016, Category.CONVERTIBLE),
new Car("Ford", "Focus", 2012, Category.SEDAN),
new Car("Chevrolet", "Geo Metro", 1992, Category.CONVERTIBLE));
}
}

View File

@ -1,30 +0,0 @@
/**
* 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.
*/
package com.iluwatar.collectionpipeline;
/**
* Enum for the category of car
*/
public enum Category {
JEEP, SEDAN, CONVERTIBLE
}

View File

@ -1,84 +0,0 @@
/**
* 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.
*/
package com.iluwatar.collectionpipeline;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
/**
* Iterating and sorting with a collection pipeline
*
* <p>In functional programming, it's common to sequence complex operations through
* a series of smaller modular functions or operations. The series is called a
* composition of functions, or a function composition. When a collection of
* data flows through a function composition, it becomes a collection pipeline.
* Function Composition and Collection Pipeline are two design patterns
* frequently used in functional-style programming.
*
* <p>Instead of passing a lambda expression to the map method, we passed the
* method reference Car::getModel. Likewise, instead of passing the lambda
* expression car -> car.getYear() to the comparing method, we passed the method
* reference Car::getYear. Method references are short, concise, and expressive.
* It is best to use them wherever possible.
*
*/
public class FunctionalProgramming {
private FunctionalProgramming() {
}
/**
* Method to get models using for collection pipeline.
*
* @param cars {@link List} of {@link Car} to be used for filtering
* @return {@link List} of {@link String} representing models built after year 2000
*/
public static List<String> getModelsAfter2000(List<Car> cars) {
return cars.stream().filter(car -> car.getYear() > 2000)
.sorted(Comparator.comparing(Car::getYear))
.map(Car::getModel).collect(Collectors.toList());
}
/**
* Method to group cars by category using groupingBy
*
* @param cars {@link List} of {@link Car} to be used for grouping
* @return {@link Map} with category as key and cars belonging to that category as value
*/
public static Map<Category, List<Car>> getGroupingOfCarsByCategory(List<Car> cars) {
return cars.stream().collect(Collectors.groupingBy(Car::getCategory));
}
/**
* Method to get all Sedan cars belonging to a group of persons sorted by year of manufacture
*
* @param persons {@link List} of {@link Person} to be used
* @return {@link List} of {@link Car} to belonging to the group
*/
public static List<Car> getSedanCarsOwnedSortedByDate(List<Person> persons) {
return persons.stream().map(Person::getCars).flatMap(List::stream)
.filter(car -> Category.SEDAN.equals(car.getCategory()))
.sorted(Comparator.comparing(Car::getYear)).collect(Collectors.toList());
}
}

View File

@ -1,131 +0,0 @@
/**
* 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.
*/
package com.iluwatar.collectionpipeline;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* Imperative-style programming to iterate over the list and get the names of
* cars made later than the year 2000. We then sort the models in ascending
* order by year.
*
* <p>As you can see, there's a lot of looping in this code. First, the
* getModelsAfter2000UsingFor method takes a list of cars as its parameter. It
* extracts or filters out cars made after the year 2000, putting them into a
* new list named carsSortedByYear. Next, it sorts that list in ascending order
* by year-of-make. Finally, it loops through the list carsSortedByYear to get
* the model names and returns them in a list.
*
* <p>This short example demonstrates what I call the effect of statements. While
* functions and methods in general can be used as expressions, the {@link Collections}
* sort method doesn't return a result. Because it is used as a statement, it
* mutates the list given as argument. Both of the for loops also mutate lists
* as they iterate. Being statements, that's just how these elements work. As a
* result, the code contains unnecessary garbage variables
*/
public class ImperativeProgramming {
private ImperativeProgramming() {
}
/**
* Method to return the car models built after year 2000 using for loops.
* @param cars {@link List} of {@link Car} to iterate over
* @return {@link List} of {@link String} of car models built after year 2000
*/
public static List<String> getModelsAfter2000(List<Car> cars) {
List<Car> carsSortedByYear = new ArrayList<>();
for (Car car : cars) {
if (car.getYear() > 2000) {
carsSortedByYear.add(car);
}
}
Collections.sort(carsSortedByYear, new Comparator<Car>() {
public int compare(Car car1, Car car2) {
return new Integer(car1.getYear()).compareTo(car2.getYear());
}
});
List<String> models = new ArrayList<>();
for (Car car : carsSortedByYear) {
models.add(car.getModel());
}
return models;
}
/**
* Method to group cars by category using for loops
*
* @param cars {@link List} of {@link Car} to be used for grouping
* @return {@link Map} with category as key and cars belonging to that category as value
*/
public static Map<Category, List<Car>> getGroupingOfCarsByCategory(List<Car> cars) {
Map<Category, List<Car>> groupingByCategory = new HashMap<>();
for (Car car: cars) {
if (groupingByCategory.containsKey(car.getCategory())) {
groupingByCategory.get(car.getCategory()).add(car);
} else {
List<Car> categoryCars = new ArrayList<>();
categoryCars.add(car);
groupingByCategory.put(car.getCategory(), categoryCars);
}
}
return groupingByCategory;
}
/**
* Method to get all Sedan cars belonging to a group of persons sorted by year of manufacture using for loops
*
* @param persons {@link List} of {@link Person} to be used
* @return {@link List} of {@link Car} to belonging to the group
*/
public static List<Car> getSedanCarsOwnedSortedByDate(List<Person> persons) {
List<Car> cars = new ArrayList<>();
for (Person person: persons) {
cars.addAll(person.getCars());
}
List<Car> sedanCars = new ArrayList<>();
for (Car car: cars) {
if (Category.SEDAN.equals(car.getCategory())) {
sedanCars.add(car);
}
}
sedanCars.sort(new Comparator<Car>() {
@Override
public int compare(Car o1, Car o2) {
return o1.getYear() - o2.getYear();
}
});
return sedanCars;
}
}

View File

@ -1,44 +0,0 @@
/**
* 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.
*/
package com.iluwatar.collectionpipeline;
import java.util.List;
/**
* A Person class that has the list of cars that the person owns and use.
*/
public class Person {
private List<Car> cars;
/**
* Constructor to create an instance of person.
* @param cars the list of cars owned
*/
public Person(List<Car> cars) {
this.cars = cars;
}
public List<Car> getCars() {
return cars;
}
}

View File

@ -1,79 +0,0 @@
/**
* 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.
*/
package com.iluwatar.collectionpipeline;
import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.junit.jupiter.api.Test;
/**
* Tests that Collection Pipeline methods work as expected.
*/
public class AppTest {
private List<Car> cars = CarFactory.createCars();
@Test
public void testGetModelsAfter2000UsingFor() {
List<String> models = ImperativeProgramming.getModelsAfter2000(cars);
assertEquals(Arrays.asList("Avenger", "Wrangler", "Focus", "Cascada"), models);
}
@Test
public void testGetModelsAfter2000UsingPipeline() {
List<String> models = FunctionalProgramming.getModelsAfter2000(cars);
assertEquals(Arrays.asList("Avenger", "Wrangler", "Focus", "Cascada"), models);
}
@Test
public void testGetGroupingOfCarsByCategory() {
Map<Category, List<Car>> modelsExpected = new HashMap<>();
modelsExpected.put(Category.CONVERTIBLE, Arrays.asList(new Car("Buick", "Cascada", 2016, Category.CONVERTIBLE),
new Car("Chevrolet", "Geo Metro", 1992, Category.CONVERTIBLE)));
modelsExpected.put(Category.SEDAN, Arrays.asList(new Car("Dodge", "Avenger", 2010, Category.SEDAN),
new Car("Ford", "Focus", 2012, Category.SEDAN)));
modelsExpected.put(Category.JEEP, Arrays.asList(new Car("Jeep", "Wrangler", 2011, Category.JEEP),
new Car("Jeep", "Comanche", 1990, Category.JEEP)));
Map<Category, List<Car>> modelsFunctional = FunctionalProgramming.getGroupingOfCarsByCategory(cars);
Map<Category, List<Car>> modelsImperative = ImperativeProgramming.getGroupingOfCarsByCategory(cars);
System.out.println("Category " + modelsFunctional);
assertEquals(modelsExpected, modelsFunctional);
assertEquals(modelsExpected, modelsImperative);
}
@Test
public void testGetSedanCarsOwnedSortedByDate() {
Person john = new Person(cars);
List<Car> modelsExpected = Arrays.asList(new Car("Dodge", "Avenger", 2010, Category.SEDAN),
new Car("Ford", "Focus", 2012, Category.SEDAN));
List<Car> modelsFunctional = FunctionalProgramming.getSedanCarsOwnedSortedByDate(Arrays.asList(john));
List<Car> modelsImperative = ImperativeProgramming.getSedanCarsOwnedSortedByDate(Arrays.asList(john));
assertEquals(modelsExpected, modelsFunctional);
assertEquals(modelsExpected, modelsImperative);
}
}

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>command</artifactId>
<dependencies>

View File

@ -33,7 +33,7 @@ Wikipedia says
Taking our sentence example from above. Here we have the base class and different printable types
```java
```
public abstract class LetterComposite {
private List<LetterComposite> children = new ArrayList<>();
public void add(LetterComposite letter) {
@ -91,7 +91,7 @@ public class Sentence extends LetterComposite {
Then we have a messenger to carry messages
```java
```
public class Messenger {
LetterComposite messageFromOrcs() {
List<Word> words = new ArrayList<>();
@ -122,7 +122,7 @@ public class Messenger {
And then it can be used as
```java
```
LetterComposite orcMessage = new Messenger().messageFromOrcs();
orcMessage.print(); // Where there is a whip there is a way.
LetterComposite elfMessage = new Messenger().messageFromElves();

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>composite</artifactId>
<dependencies>

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Before

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After

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@ -29,7 +29,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<dependencies>

View File

@ -50,37 +50,37 @@ public class Converter<T, U> {
}
/**
* @param dto DTO entity
* @param userDto DTO entity
* @return The domain representation - the result of the converting function application on dto entity.
*/
public final U convertFromDto(final T dto) {
return fromDto.apply(dto);
public final U convertFromDto(final T userDto) {
return fromDto.apply(userDto);
}
/**
* @param entity domain entity
* @param user domain entity
* @return The DTO representation - the result of the converting function application on domain entity.
*/
public final T convertFromEntity(final U entity) {
return fromEntity.apply(entity);
public final T convertFromEntity(final U user) {
return fromEntity.apply(user);
}
/**
* @param dtos collection of DTO entities
* @param dtoUsers collection of DTO entities
* @return List of domain representation of provided entities retrieved by
* mapping each of them with the conversion function
*/
public final List<U> createFromDtos(final Collection<T> dtos) {
return dtos.stream().map(this::convertFromDto).collect(Collectors.toList());
public final List<U> createFromDtos(final Collection<T> dtoUsers) {
return dtoUsers.stream().map(this::convertFromDto).collect(Collectors.toList());
}
/**
* @param entities collection of domain entities
* @param users collection of domain entities
* @return List of domain representation of provided entities retrieved by
* mapping each of them with the conversion function
*/
public final List<T> createFromEntities(final Collection<U> entities) {
return entities.stream().map(this::convertFromEntity).collect(Collectors.toList());
public final List<T> createFromEntities(final Collection<U> users) {
return users.stream().map(this::convertFromEntity).collect(Collectors.toList());
}
}

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@ -21,7 +21,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>cqrs</artifactId>
<dependencies>

View File

@ -30,7 +30,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>dao</artifactId>

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@ -33,7 +33,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>data-bus</artifactId>
<dependencies>

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@ -28,7 +28,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>data-mapper</artifactId>
<dependencies>

View File

@ -28,7 +28,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>data-transfer-object</artifactId>
<dependencies>

View File

@ -36,7 +36,7 @@ Wikipedia says
Let's take the troll example. First of all we have a simple troll implementing the troll interface
```java
```
public interface Troll {
void attack();
int getAttackPower();
@ -66,7 +66,7 @@ public class SimpleTroll implements Troll {
Next we want to add club for the troll. We can do it dynamically by using a decorator
```java
```
public class ClubbedTroll implements Troll {
private static final Logger LOGGER = LoggerFactory.getLogger(ClubbedTroll.class);
@ -97,7 +97,7 @@ public class ClubbedTroll implements Troll {
Here's the troll in action
```java
```
// simple troll
Troll troll = new SimpleTroll();
troll.attack(); // The troll tries to grab you!

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@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>decorator</artifactId>
<dependencies>

View File

@ -30,7 +30,7 @@
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>dependency-injection</artifactId>
<dependencies>

View File

@ -1,26 +0,0 @@
---
layout: pattern
title: Dirty Flag
folder: dirty-flag
permalink: /patterns/dirty-flag/
categories: Other
tags:
- Java
- Difficulty-Beginner
- Performance
---
## Intent
To avoid expensive re-acquisition of resources. The resources retain their identity, are kept in some
fast-access storage, and are re-used to avoid having to acquire them again.
![alt text](./etc/dirty-flag.png "Dirty Flag")
## Applicability
Use the Dirty Flag pattern when
* Repetitious acquisition, initialization, and release of the same resource causes unnecessary performance overhead.
## Credits
* [Design Patterns: Dirty Flag](https://www.takeupcode.com/podcast/89-design-patterns-dirty-flag/)

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@ -1,45 +0,0 @@
<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.2.2" 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.dirtyflag.App" project="dirty-flag"
file="/dirty-flag/src/main/java/com/iluwatar/dirtyflag/App.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="266" y="188"/>
<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.dirtyflag.DataFetcher" project="dirty-flag"
file="/dirty-flag/src/main/java/com/iluwatar/dirtyflag/DataFetcher.java" binary="false" corner="BOTTOM_RIGHT">
<position height="153" width="125" x="66" y="291"/>
<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.dirtyflag.World" project="dirty-flag"
file="/dirty-flag/src/main/java/com/iluwatar/dirtyflag/World.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="379" y="366"/>
<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="4">
<end type="SOURCE" refId="3" navigable="false">
<attribute id="5" name="df"/>
<multiplicity id="6" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="2" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<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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@ -1,54 +0,0 @@
<?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>1.21.0-SNAPSHOT</version>
</parent>
<groupId>com.iluwatar</groupId>
<artifactId>dirty-flag</artifactId>
<version>1.21.0-SNAPSHOT</version>
<name>dirty-flag</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-api</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-engine</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>

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@ -1,82 +0,0 @@
/**
* The MIT License
* Copyright (c) 2014-2016 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.dirtyflag;
import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
/**
*
* This application demonstrates the <b>Dirty Flag</b> pattern. The dirty flag behavioral pattern allows you to avoid
* expensive operations that would just need to be done again anyway. This is a simple pattern that really just explains
* how to add a bool value to your class that you can set anytime a property changes. This will let your class know that
* any results it may have previously calculated will need to be calculated again when theyre requested. Once the
* results are re-calculated, then the bool value can be cleared.
*
* There are some points that need to be considered before diving into using this pattern:- there are some things youll
* need to consider:- (1) Do you need it? This design pattern works well when the results to be calculated are difficult
* or resource intensive to compute. You want to save them. You also dont want to be calculating them several times in
* a row when only the last one counts. (2) When do you set the dirty flag? Make sure that you set the dirty flag within
* the class itself whenever an important property changes. This property should affect the result of the calculated
* result and by changing the property, that makes the last result invalid. (3) When do you clear the dirty flag? It
* might seem obvious that the dirty flag should be cleared whenever the result is calculated with up-to-date
* information but there are other times when you might want to clear the flag.
*
* In this example, the {@link DataFetcher} holds the <i>dirty flag</i>. It fetches and re-fetches from <i>world.txt</i>
* when needed. {@link World} mainly serves the data to the front-end.
*/
public class App {
/**
* Program execution point
*/
public void run() {
final ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
executorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
World world = new World();
List<String> countries = world.fetch();
System.out.println("Our world currently has the following countries:-");
for (String country : countries) {
System.out.println("\t" + country);
}
}
}, 0, 15, TimeUnit.SECONDS); // Run at every 15 seconds.
}
/**
* Program entry point
*
* @param args
* command line args
*/
public static void main(String[] args) {
App app = new App();
app.run();
}
}

View File

@ -1,81 +0,0 @@
/**
* 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.
*/
package com.iluwatar.dirtyflag;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
/**
* A mock database manager -- Fetches data from a raw file.
*
* @author swaisuan
*
*/
public class DataFetcher {
private final String filename = "world.txt";
private long lastFetched;
public DataFetcher() {
this.lastFetched = -1;
}
private boolean isDirty(long fileLastModified) {
if (lastFetched != fileLastModified) {
lastFetched = fileLastModified;
return true;
}
return false;
}
/**
* Fetches data/content from raw file.
*
* @return List of strings
*/
public List<String> fetch() {
ClassLoader classLoader = getClass().getClassLoader();
File file = new File(classLoader.getResource(filename).getFile());
if (isDirty(file.lastModified())) {
System.out.println(filename + " is dirty! Re-fetching file content...");
List<String> data = new ArrayList<String>();
try (BufferedReader br = new BufferedReader(new FileReader(file))) {
String line;
while ((line = br.readLine()) != null) {
data.add(line);
}
} catch (IOException e) {
e.printStackTrace();
}
return data;
}
return new ArrayList<String>();
}
}

View File

@ -1,58 +0,0 @@
/**
* 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.
*/
package com.iluwatar.dirtyflag;
import java.util.ArrayList;
import java.util.List;
/**
*
* A middle-layer app that calls/passes along data from the back-end.
*
* @author swaisuan
*
*/
public class World {
private List<String> countries;
private DataFetcher df;
public World() {
this.countries = new ArrayList<String>();
this.df = new DataFetcher();
}
/**
*
* Calls {@link DataFetcher} to fetch data from back-end.
*
* @return List of strings
*/
public List<String> fetch() {
List<String> data = df.fetch();
countries = data.isEmpty() ? countries : data;
return countries;
}
}

View File

@ -1,40 +0,0 @@
/**
* The MIT License
* 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
* 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 org.dirty.flag;
import java.io.IOException;
import org.junit.jupiter.api.Test;
import com.iluwatar.dirtyflag.App;
/**
* Tests that Dirty-Flag example runs without errors.
*/
public class AppTest {
@Test
public void test() throws IOException {
String[] args = {};
App.main(args);
}
}

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@ -1,54 +0,0 @@
/**
* The MIT License
* 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
* 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 org.dirty.flag;
import static org.junit.jupiter.api.Assertions.assertTrue;
import java.util.List;
import org.junit.jupiter.api.Test;
import com.iluwatar.dirtyflag.DataFetcher;
/**
*
* Application test
*
*/
public class DirtyFlagTest {
@Test
public void testIsDirty() {
DataFetcher df = new DataFetcher();
List<String> countries = df.fetch();
assertTrue(!countries.isEmpty());
}
@Test
public void testIsNotDirty() {
DataFetcher df = new DataFetcher();
df.fetch();
List<String> countries = df.fetch();
assertTrue(countries.isEmpty());
}
}

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@ -27,7 +27,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>double-checked-locking</artifactId>
<dependencies>

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>double-dispatch</artifactId>
<dependencies>

View File

@ -26,7 +26,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<dependencies>

View File

@ -26,7 +26,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<dependencies>

View File

@ -26,7 +26,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<dependencies>

View File

@ -28,7 +28,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>event-aggregator</artifactId>
<dependencies>

View File

@ -29,7 +29,7 @@
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.21.0-SNAPSHOT</version>
<version>1.19.0-SNAPSHOT</version>
</parent>
<artifactId>event-asynchronous</artifactId>
<dependencies>

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