JDK中的设计模式应用实例

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在JDK(Java Development Kit)类库中，开发人员使用了大量设计模式，正因为如此，我们可以在不修改JDK源码的前提下开发出自己的应用软件，本文列出了部分JDK中的模式应用实例，有兴趣的童鞋可以深入研究，看看前Sun公司的开发人员是如何在实际框架开发中运用设计模式的，，Sunny认为，研究JDK类库中的模式实例也不失为学习如何使用设计模式的一个好方式，。

创建型模式：

(1) 抽象工厂模式(Abstract Factory)

• java.util.Calendar#getInstance()

• java.util.Arrays#asList()

• java.util.ResourceBundle#getBundle()

• java.net.URL#openConnection()

• java.sql.DriverManager#getConnection()

• java.sql.Connection#createStatement()

• java.sql.Statement#executeQuery()

• java.text.NumberFormat#getInstance()

• java.lang.management.ManagementFactory (所有getXXX()方法)

• java.nio.charset.Charset#forName()

• javax.xml.parsers.DocumentBuilderFactory#newInstance()

• javax.xml.transform.TransformerFactory#newInstance()

• javax.xml.xpath.XPathFactory#newInstance()

(2) 建造者模式(Builder)

• java.lang.StringBuilder#append()

• java.lang.StringBuffer#append()

• java.nio.ByteBuffer#put() (CharBuffer, ShortBuffer, IntBuffer,LongBuffer, FloatBuffer和DoubleBuffer与之类似)

• javax.swing.GroupLayout.Group#addComponent()

• java.sql.PreparedStatement

• java.lang.Appendable的所有实现类

(3) 工厂方法模式(Factory Method)

• java.lang.Object#toString() (在其子类中可以覆盖该方法)

• java.lang.Class#newInstance()

• java.lang.Integer#valueOf(String) (Boolean, Byte, Character,Short, Long, Float和 Double与之类似)

• java.lang.Class#forName()

• java.lang.reflect.Array#newInstance()

• java.lang.reflect.Constructor#newInstance()

(4) 原型模式(Prototype)

• java.lang.Object#clone() (支持浅克隆的类必须实现java.lang.Cloneable接口)

(5) 单例模式 (Singleton)

• java.lang.Runtime#getRuntime()

• java.awt.Desktop#getDesktop()

结构型模式：

(1) 适配器模式(Adapter)

•java.util.Arrays#asList()

•javax.swing.JTable(TableModel)

•java.io.InputStreamReader(InputStream)

•java.io.OutputStreamWriter(OutputStream)

•javax.xml.bind.annotation.adapters.XmlAdapter#marshal()

•javax.xml.bind.annotation.adapters.XmlAdapter#unmarshal()

(2) 桥接模式(Bridge)

• AWT (提供了抽象层映射于实际的操作系统)

•JDBC

(3) 组合模式(Composite)

•javax.swing.JComponent#add(Component)

•java.awt.Container#add(Component)

•java.util.Map#putAll(Map)

•java.util.List#addAll(Collection)

•java.util.Set#addAll(Collection)

(4) 装饰模式(Decorator)

•java.io.BufferedInputStream(InputStream)

•java.io.DataInputStream(InputStream)

•java.io.BufferedOutputStream(OutputStream)

•java.util.zip.ZipOutputStream(OutputStream)

•java.util.Collections#checked[List|Map|Set|SortedSet|SortedMap]()

(5) 外观模式(Facade)

•java.lang.Class

•javax.faces.webapp.FacesServlet

(6) 享元模式(Flyweight)

•java.lang.Integer#valueOf(int)

•java.lang.Boolean#valueOf(boolean)

• java.lang.Byte#valueOf(byte)

•java.lang.Character#valueOf(char)

(7) 代理模式(Proxy)

• java.lang.reflect.Proxy

•java.rmi.*

行为型模式：

(1) 职责链模式(Chain of Responsibility)

•java.util.logging.Logger#log()

•javax.servlet.Filter#doFilter()

(2) 命令模式(Command)

• java.lang.Runnable

• javax.swing.Action

(3) 解释器模式(Interpreter)

• java.util.Pattern

• java.text.Normalizer

• java.text.Format

• javax.el.ELResolver

(4) 迭代器模式(Iterator)

• java.util.Iterator

• java.util.Enumeration

(5) 中介者模式(Mediator)

• java.util.Timer (所有scheduleXXX()方法)

• java.util.concurrent.Executor#execute()

• java.util.concurrent.ExecutorService (invokeXXX()和submit()方法)

• java.util.concurrent.ScheduledExecutorService (所有scheduleXXX()方法)

•java.lang.reflect.Method#invoke()

(6) 备忘录模式(Memento)

•java.util.Date

•java.io.Serializable

•javax.faces.component.StateHolder

(7) 观察者模式(Observer)

•java.util.Observer/java.util.Observable

•java.util.EventListener (所有子类)

•javax.servlet.http.HttpSessionBindingListener

•javax.servlet.http.HttpSessionAttributeListener

•javax.faces.event.PhaseListener

(8) 状态模式(State)

•java.util.Iterator

•javax.faces.lifecycle.LifeCycle#execute()

(9) 策略模式(Strategy)

• java.util.Comparator#compare()

• javax.servlet.http.HttpServlet

• javax.servlet.Filter#doFilter()

(10) 模板方法模式(Template Method)

•java.io.InputStream, java.io.OutputStream, java.io.Reader和java.io.Writer的所有非抽象方法

•java.util.AbstractList, java.util.AbstractSet和java.util.AbstractMap的所有非抽象方法

•javax.servlet.http.HttpServlet#doXXX()

(11) 访问者模式(Visitor)

•javax.lang.model.element.AnnotationValue和AnnotationValueVisitor

•javax.lang.model.element.Element和ElementVisitor

•javax.lang.model.type.TypeMirror和TypeVisitor

参见：http://www.iteye.com/news/18725和http://stackoverflow.com/questions/1673841/examples-of-gof-design-patterns。

【作者：刘伟 http://blog.csdn.net/lovelion】

－－－－－－－－－－－－－－－－－－－－－－－蛋疼的分割线－－－－－－－－－－－－－－－－－－－－－－－－－

Creational patterns

Abstract factory ^{_{(recognizeable by creational methods returning the factory itself which in turn can be used to create another abstract/interface type)}}

javax.xml.parsers.DocumentBuilderFactory#newInstance()
javax.xml.transform.TransformerFactory#newInstance()
javax.xml.xpath.XPathFactory#newInstance()

Builder ^{_{(recognizeable by creational methods returning the instance itself)}}

java.lang.StringBuilder#append() (unsynchronized)
java.lang.StringBuffer#append() (synchronized)
java.nio.ByteBuffer#put() (also on CharBuffer, ShortBuffer, IntBuffer, LongBuffer,FloatBuffer and DoubleBuffer)
javax.swing.GroupLayout.Group#addComponent()
All implementations of java.lang.Appendable

Factory method ^{_{(recognizeable by creational methods returning an implementation of an abstract/interface type)}}

java.util.Calendar#getInstance()
java.util.ResourceBundle#getBundle()
java.text.NumberFormat#getInstance()
java.nio.charset.Charset#forName()
java.net.URLStreamHandlerFactory#createURLStreamHandler(String) (Returns singleton object per protocol)

Prototype ^{_{(recognizeable by creational methods returning a different instance of itself with the same properties)}}

java.lang.Object#clone() (the class has to implement java.lang.Cloneable)

Singleton ^{_{(recognizeable by creational methods returning the same instance (usually of itself) everytime)}}

java.lang.Runtime#getRuntime()
java.awt.Desktop#getDesktop()

Structural patterns

Adapter ^{_{(recognizeable by creational methods taking an instance of different abstract/interface type and returning an implementation of own/another abstract/interface type which decorates/overrides the given instance)}}

java.util.Arrays#asList()
java.io.InputStreamReader(InputStream) (returns a Reader)
java.io.OutputStreamWriter(OutputStream) (returns a Writer)
javax.xml.bind.annotation.adapters.XmlAdapter#marshal() and #unmarshal()

Bridge ^{_{(recognizeable by creational methods taking an instance of different abstract/interface type and returning an implementation of own abstract/interface type which delegates/uses the given instance)}}

None comes to mind yet. A fictive example would be new LinkedHashMap(LinkedHashSet<K>, List<V>) which returns an unmodifiable linked map which doesn't clone the items, but uses them. The java.util.Collections#newSetFromMap() and singletonXXX() methods however comes close.

Composite ^{_{(recognizeable by behavioral methods taking an instance of same abstract/interface type into a tree structure)}}

java.awt.Container#add(Component) (practically all over Swing thus)
javax.faces.component.UIComponent#getChildren() (practically all over JSF UI thus)

Decorator ^{_{(recognizeable by creational methods taking an instance of same abstract/interface type which adds additional behaviour)}}

All subclasses of java.io.InputStream, OutputStream, Reader and Writer have a constructor taking an instance of same type.
java.util.Collections, the checkedXXX(), synchronizedXXX() and unmodifiableXXX()methods.
javax.servlet.http.HttpServletRequestWrapper and HttpServletResponseWrapper

Facade ^{_{(recognizeable by behavioral methods which internally uses instances of different independent abstract/interface types)}}

javax.faces.context.FacesContext, it internally uses among others the abstract/interface types LifeCycle, ViewHandler, NavigationHandler and many more without that the enduser has to worry about it (which are however overrideable by injection).
javax.faces.context.ExternalContext, which internally uses ServletContext,HttpSession, HttpServletRequest, HttpServletResponse, etc.

Flyweight ^{_{(recognizeable by creational methods returning a cached instance, a bit the "multiton" idea)}}

java.lang.Integer#valueOf(int) (also on Boolean, Byte, Character, Short and Long)

Proxy ^{_{(recognizeable by creational methods which returns an implementation of given abstract/interface type which in turn delegates/uses a different implementation of given abstract/interface type)}}

java.lang.reflect.Proxy
java.rmi.*, the whole API actually.

^{_{The Wikipedia example is IMHO a bit poor, lazy loading has actually completely nothing to do with the proxy pattern at all.}}

Behavioral patterns

Chain of responsibility ^{_{(recognizeable by behavioral methods which (indirectly) invokes the same method inanother implementation of same abstract/interface type in a queue)}}

java.util.logging.Logger#log()
javax.servlet.Filter#doFilter()

Command ^{_{(recognizeable by behavioral methods in an abstract/interface type which invokes a method in an implementation of a different abstract/interface type which has been encapsulated by the command implementation during its creation)}}

All implementations of java.lang.Runnable
All implementations of javax.swing.Action

Interpreter ^{_{(recognizeable by behavioral methods returning a structurally different instance/type of the given instance/type; note that parsing/formatting is not part of the pattern, determining the pattern and how to apply it is)}}

java.util.Pattern
java.text.Normalizer
All subclasses of java.text.Format
All subclasses of javax.el.ELResolver

Iterator ^{_{(recognizeable by behavioral methods sequentially returning instances of a different type from a queue)}}

All implementations of java.util.Iterator (thus among others also java.util.Scanner!).
All implementations of java.util.Enumeration

Mediator ^{_{(recognizeable by behavioral methods taking an instance of different abstract/interface type (usually using the command pattern) which delegates/uses the given instance)}}

java.util.Timer (all scheduleXXX() methods)
java.util.concurrent.Executor#execute()
java.util.concurrent.ExecutorService (the invokeXXX() and submit() methods)
java.util.concurrent.ScheduledExecutorService (all scheduleXXX() methods)
java.lang.reflect.Method#invoke()

Memento ^{_{(recognizeable by behavioral methods which internally changes the state of the whole instance)}}

java.util.Date (the setter methods do that, Date is internally represented by a long value)
All implementations of java.io.Serializable
All implementations of javax.faces.component.StateHolder

Observer (or Publish/Subscribe) ^{_{(recognizeable by behavioral methods which invokes a method on an instance of another abstract/interface type, depending on own state)}}

java.util.Observer/java.util.Observable (rarely used in real world though)
All implementations of java.util.EventListener (practically all over Swing thus)
javax.servlet.http.HttpSessionBindingListener
javax.servlet.http.HttpSessionAttributeListener
javax.faces.event.PhaseListener

State ^{_{(recognizeable by behavioral methods which changes its behaviour depending on the instance's state which can be controlled externally)}}

javax.faces.lifecycle.LifeCycle#execute() (controlled by FacesServlet, the behaviour is dependent on current phase (state) of JSF lifecycle)

Strategy ^{_{(recognizeable by behavioral methods in an abstract/interface type which invokes a method in an implementation of a different abstract/interface type which has been passed-in as method argument into the strategy implementation)}}

java.util.Comparator#compare(), executed by among others Collections#sort().
javax.servlet.http.HttpServlet, the service() and all doXXX() methods takeHttpServletRequest and HttpServletResponse and the implementor has to process them (and not to get hold of them as instance variables!).
javax.servlet.Filter#doFilter()

Template method ^{_{(recognizeable by behavioral methods which already have a "default" behaviour definied by an abstract type)}}

All non-abstract methods of java.io.InputStream, java.io.OutputStream, java.io.Readerand java.io.Writer.
All non-abstract methods of java.util.AbstractList, java.util.AbstractSet andjava.util.AbstractMap.
javax.servlet.http.HttpServlet, all the doXXX() methods by default sends a HTTP 405 "Method Not Allowed" error to the response. You're free to implement none or any of them.

Visitor ^{_{(recognizeable by two different abstract/interface types which has methods definied which takes each theother abstract/interface type; the one actually calls the method of the other and the other executes the desired strategy on it)}}

javax.lang.model.element.AnnotationValue and AnnotationValueVisitor
javax.lang.model.element.Element and ElementVisitor
javax.lang.model.type.TypeMirror and TypeVisitor

转：

参见：http://www.iteye.com/news/18725和http://stackoverflow.com/questions/1673841/examples-of-gof-design-patterns。

【作者：刘伟 http://blog.csdn.net/lovelion】

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JDK中的设计模式应用实例

Creational patterns

Abstract factory (recognizeable by creational methods returning the factory itself which in turn can be used to create another abstract/interface type)

Builder (recognizeable by creational methods returning the instance itself)

Factory method (recognizeable by creational methods returning an implementation of an abstract/interface type)

Prototype (recognizeable by creational methods returning a different instance of itself with the same properties)

Singleton (recognizeable by creational methods returning the same instance (usually of itself) everytime)

Structural patterns

Adapter (recognizeable by creational methods taking an instance of different abstract/interface type and returning an implementation of own/another abstract/interface type which decorates/overrides the given instance)

Bridge (recognizeable by creational methods taking an instance of different abstract/interface type and returning an implementation of own abstract/interface type which delegates/uses the given instance)

Composite (recognizeable by behavioral methods taking an instance of same abstract/interface type into a tree structure)

Decorator (recognizeable by creational methods taking an instance of same abstract/interface type which adds additional behaviour)

Facade (recognizeable by behavioral methods which internally uses instances of different independent abstract/interface types)

Flyweight (recognizeable by creational methods returning a cached instance, a bit the "multiton" idea)

Proxy (recognizeable by creational methods which returns an implementation of given abstract/interface type which in turn delegates/uses a different implementation of given abstract/interface type)

Behavioral patterns

Chain of responsibility (recognizeable by behavioral methods which (indirectly) invokes the same method inanother implementation of same abstract/interface type in a queue)

Command (recognizeable by behavioral methods in an abstract/interface type which invokes a method in an implementation of a different abstract/interface type which has been encapsulated by the command implementation during its creation)

Interpreter (recognizeable by behavioral methods returning a structurally different instance/type of the given instance/type; note that parsing/formatting is not part of the pattern, determining the pattern and how to apply it is)

Iterator (recognizeable by behavioral methods sequentially returning instances of a different type from a queue)

Mediator (recognizeable by behavioral methods taking an instance of different abstract/interface type (usually using the command pattern) which delegates/uses the given instance)

Memento (recognizeable by behavioral methods which internally changes the state of the whole instance)

Observer (or Publish/Subscribe) (recognizeable by behavioral methods which invokes a method on an instance of another abstract/interface type, depending on own state)

State (recognizeable by behavioral methods which changes its behaviour depending on the instance's state which can be controlled externally)

Strategy (recognizeable by behavioral methods in an abstract/interface type which invokes a method in an implementation of a different abstract/interface type which has been passed-in as method argument into the strategy implementation)

Template method (recognizeable by behavioral methods which already have a "default" behaviour definied by an abstract type)

Visitor (recognizeable by two different abstract/interface types which has methods definied which takes each theother abstract/interface type; the one actually calls the method of the other and the other executes the desired strategy on it)