JDK中的设计模式应用实例

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
take

HttpServletRequest

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.Reader

and

java.io.Writer

.

All non-abstract methods of

java.util.AbstractList

,

java.util.AbstractSet

and

java.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】