gaspersic/java-design-patterns
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Merge pull request #678 from Tschis/presentations

Browse Source 
Add presentation for Command and Factory Method
This commit is contained in:
Ilkka Seppälä
2017-12-15 21:25:49 +02:00
committed by GitHub
parent 6614d0735e 7e7a0c83f5
commit 11de22bf4a
6 changed files with 437 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
command/README.md
View File

@ -36,6 +36,10 @@ Use the Command pattern when you want to
* implement callback functionality * implement callback functionality
* implement the undo functionality * implement the undo functionality
## Presentations
* [Command Pattern](etc/presentation.html)
## Real world examples ## Real world examples
* [java.lang.Runnable](http://docs.oracle.com/javase/8/docs/api/java/lang/Runnable.html) * [java.lang.Runnable](http://docs.oracle.com/javase/8/docs/api/java/lang/Runnable.html)

BIN
command/etc/diagram.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 56 KiB

243
command/etc/presentation.html Normal file
View File

@ -0,0 +1,243 @@
<!--
The MIT License
Copyright (c) 2017 Rodolfo Forte
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.
-->
<!DOCTYPE html>
<html>
<head>
<title>Design Patterns - Command Presentation</title>
<meta charset="utf-8">
<style>
@import url(https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz);
@import url(https://fonts.googleapis.com/css?family=Droid+Serif:400,700,400italic);
@import url(https://fonts.googleapis.com/css?family=Ubuntu+Mono:400,700,400italic);
body { font-family: 'Droid Serif'; }
h1, h2, h3 {
font-family: 'Yanone Kaffeesatz';
font-weight: normal;
}
.remark-code, .remark-inline-code { font-family: 'Ubuntu Mono'; }
blockquote {
border-left: 0.3em solid rgba(0,0,0,0.5);
padding: 0 15px;
font-style: italic;
}
img {
max-width:100%;
}
</style>
</head>
<body>
<textarea id="source">
class: center, middle
# Command
---
# Also known as
* Action, Transaction
---
# Intent
* Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.
---
# Explanation
* [Wikipedia](https://en.wikipedia.org/wiki/Command_pattern) says:
> In object-oriented programming, the command pattern is a behavioral design pattern in which an object is used to encapsulate all information needed to perform an action or trigger an event at a later time. This information includes the method name, the object that owns the method and values for the method parameters.
<br />
* In plain words:
* Enable the construction of components that are able to delegate, sequence or execute method calls at a time of their choosing;
---
# Explanation
Four terms always associated with the pattern:
* Command
* Object that knows about the receiver and invokes a method of the receiver;
* Receiver
* Object that does the work;
* Invoker
* Knows how to execute a command, and optionally does the bookkeeping about the command execution;
* Client
* Decides which commands to execute at which points, passing the command object to the invoker object;
---
# Example
In our example, a Wizard can cast spells on targets.
* Spell will be the command (implements the Command interface);
* Goblin (a Target object) will be the receiver;
* Wizard will be the invoker;
* App will be the client;
```
//App.java
public static void main(String[] args) {
Wizard wizard = new Wizard();
Goblin goblin = new Goblin();
goblin.printStatus(); //Goblin, [size=normal] [visibility=visible]
wizard.castSpell(new ShrinkSpell(), goblin);
wizard.castSpell(new InvisibilitySpell(), goblin);
goblin.printStatus(); //Goblin, [size=small] [visibility=invisible]
wizard.undoLastSpell();
goblin.printStatus(); //Goblin, [size=small] [visibility=visible]
wizard.redoLastSpell();
goblin.printStatus(); //Goblin, [size=small] [visibility=invisible]
}
```
---
# Diagram
.center[![Diagram](diagram.png)]
---
# Applicability
Use the Command pattern when you want to:
* Parameterize objects by an action to perform;
* You can express such parameterization in a procedural language with a callback function, that is, a function that's registered somewhere to be called at a later point;
* Commands are an object-oriented replacement for callbacks;
<br />
* Specify, queue, and execute requests at different times;
* A Command object can have a lifetime independent of the original request;
* If the receiver of a request can be represented in an address space-independent way, then you can transfer a command object for the request to a different process and fulfill the request there;
---
# Applicability
Use the Command pattern when you want to:
* Support undo;
* The Command's execute() operation can store state for reversing its effects in the command itself;
* The Command interface must have an added unexecute() operation that reverses the effects of a previous call to execute;
* Executed commands are stored in a history list;
* Unlimited-level undo and redo is achieved by traversing this list backwards and forwards calling unexecute() and execute(), respectively;
---
# Applicability
Use the Command pattern when you want to:
* Support logging changes so that they can be reapplied in case of a system crash;
* By augmenting the Command interface with load() and store() operations, you can keep a persistent log of changes;
* Recovering from a crash involves reloading logged commands from disk and re-executing them with the execute operation;
---
# Applicability
Use the Command pattern when you want to:
* Structure a system around high-level operations build on primitive operations;
* Such a structure is common in information systems that support transactions;
* A transaction encapsulates a set of changes to data;
* The Command pattern offers a way to model transactions;
* Commands have a common interface, letting you invoke all transactions the same way;
* The pattern also makes it easy to extend the system with new transactions
---
# Use Cases
* To keep a history of requests;
* Implement callback functionality;
* Implement the undo functionality;
---
# Real world examples
[java.lang.Runnable](http://docs.oracle.com/javase/8/docs/api/java/lang/Runnable.html)
[Netflix Hystrix](https://github.com/Netflix/Hystrix/wiki)
[javax.swing.Action](http://docs.oracle.com/javase/8/docs/api/javax/swing/Action.html)
---
# Credits
* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
---
# Tutorials
* Source code http://java-design-patterns.com/patterns/command/
</textarea>
<script src="https://gnab.github.io/remark/downloads/remark-latest.min.js">
</script>
<script>
var slideshow = remark.create();
</script>
</body>
</html>

6
factory-method/README.md
View File

@ -69,7 +69,11 @@ Use the Factory Method pattern when
* a class wants its subclasses to specify the objects it creates * a class wants its subclasses to specify the objects it creates
* classes delegate responsibility to one of several helper subclasses, and you want to localize the knowledge of which helper subclass is the delegate * classes delegate responsibility to one of several helper subclasses, and you want to localize the knowledge of which helper subclass is the delegate
## Known uses ## Presentations
* [Factory Method Pattern](etc/presentation.html)
## Real world examples
* [java.util.Calendar](http://docs.oracle.com/javase/8/docs/api/java/util/Calendar.html#getInstance--) * [java.util.Calendar](http://docs.oracle.com/javase/8/docs/api/java/util/Calendar.html#getInstance--)
* [java.util.ResourceBundle](http://docs.oracle.com/javase/8/docs/api/java/util/ResourceBundle.html#getBundle-java.lang.String-) * [java.util.ResourceBundle](http://docs.oracle.com/javase/8/docs/api/java/util/ResourceBundle.html#getBundle-java.lang.String-)

BIN
factory-method/etc/diagram1.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 58 KiB

185
factory-method/etc/presentation.html Normal file
View File

@ -0,0 +1,185 @@
<!--
The MIT License
Copyright (c) 2017 Rodolfo Forte
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.
-->
<!DOCTYPE html>
<html>
<head>
<title>Design Patterns - Factory Method Presentation</title>
<meta charset="utf-8">
<style>
@import url(https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz);
@import url(https://fonts.googleapis.com/css?family=Droid+Serif:400,700,400italic);
@import url(https://fonts.googleapis.com/css?family=Ubuntu+Mono:400,700,400italic);
body { font-family: 'Droid Serif'; }
h1, h2, h3 {
font-family: 'Yanone Kaffeesatz';
font-weight: normal;
}
.remark-code, .remark-inline-code { font-family: 'Ubuntu Mono'; }
blockquote {
border-left: 0.3em solid rgba(0,0,0,0.5);
padding: 0 15px;
font-style: italic;
}
img {
max-width:100%;
}
</style>
</head>
<body>
<textarea id="source">
class: center, middle
# Factory Method
---
# Also known as
* Virtual Constructor
---
# Intent
* Define an interface for creating an object, but let subclasses decide which class to instantiate;
* Factory Method lets a class defer instantiation to subclasses;
---
# Explanation
* [Wikipedia](https://en.wikipedia.org/wiki/Factory_method_pattern) says:
> "In class-based programming, the factory method pattern is a creational pattern that uses factory methods to deal with the problem of creating objects without having to specify the exact class of the object that will be created. This is done by creating objects by calling a factory method (either specified in an interface and implemented by child classes, or implemented in a base class and optionally overridden by derived classes) rather than by calling a constructor."
* In plain words:
* It provides a way to delegate the instantiation logic to child classes;
---
# Example
* Blacksmith manufactures weapons;
* Elves require Elvish weapons and Orcs require Orcish weapons;
* Depending on the customer at hand, the right type of blacksmith is summoned and, consequently, the right type of weapon;
---
# Programmatic Example
Considering the blacksmith example, we have a blacksmith interface and some implementations for it:
<br />
```
public interface Blacksmith {
Weapon manufactureWeapon(WeaponType weaponType);
}
public class ElfBlacksmith implements Blacksmith {
public Weapon manufactureWeapon(WeaponType weaponType) {
return new ElfWeapon(weaponType);
}
}
public class OrcBlacksmith implements Blacksmith {
public Weapon manufactureWeapon(WeaponType weaponType) {
return new OrcWeapon(weaponType);
}
}
```
---
# Programmatic Example
Now, as the customers come, the correct type of blacksmith is summoned and weapons are instantiated via the factory method `manufactureWeapon()`:
<br />
```
Blacksmith blacksmith = new ElfBlacksmith();
blacksmith.manufactureWeapon(WeaponType.SPEAR);
blacksmith.manufactureWeapon(WeaponType.AXE);
// Elvish weapons are created
```
---
# Diagram
* The diagram below showcases the example:
.center[![Diagram](diagram1.png)]
---
# Applicability
Use the Factory Method pattern when:
* A class can't anticipate the class of objects it must create;
* A class wants its subclasses to specify the objects it creates;
* Classes delegate responsibility to one of several helper subclasses, and you want to localize the knowledge of which helper subclass is the delegate;
---
# Real world examples
* [java.util.Calendar](http://docs.oracle.com/javase/8/docs/api/java/util/Calendar.html#getInstance--)
* [java.util.ResourceBundle](http://docs.oracle.com/javase/8/docs/api/java/util/ResourceBundle.html#getBundle-java.lang.String-)
* [java.text.NumberFormat](http://docs.oracle.com/javase/8/docs/api/java/text/NumberFormat.html#getInstance--)
* [java.nio.charset.Charset](http://docs.oracle.com/javase/8/docs/api/java/nio/charset/Charset.html#forName-java.lang.String-)
* [java.net.URLStreamHandlerFactory](http://docs.oracle.com/javase/8/docs/api/java/net/URLStreamHandlerFactory.html#createURLStreamHandler-java.lang.String-)
* [java.util.EnumSet](https://docs.oracle.com/javase/8/docs/api/java/util/EnumSet.html#of-E-)
* [javax.xml.bind.JAXBContext](https://docs.oracle.com/javase/8/docs/api/javax/xml/bind/JAXBContext.html#createMarshaller--)
---
# Credits
* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
---
# Tutorials
* Source code http://java-design-patterns.com/patterns/factory-method/
</textarea>
<script src="https://gnab.github.io/remark/downloads/remark-latest.min.js">
</script>
<script>
var slideshow = remark.create();
</script>
</body>
</html>