Java中的設計模式

時間 2019-11-15

標籤 java 設計模式欄目 Java 简体版

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《設計模式：可複用面向對象軟件的基礎》一書中提出了24中經典的設計模式，這些設計模式被普遍地運用於項目實戰之中。這篇博客的重點並不在於講解這些設計模式以及使用，而主要列舉了在Java Core Libraries中間所用到的設計模式。Java Core Libraries中的API設計基本涵蓋了GOF書中所提到的絕大部分設計模式，能夠說是API設計的典範，很是值得借鑑和學習。java

建立型模式

這些設計模式提供了一種在建立對象的同時隱藏建立邏輯的方式，而不是使用 new 運算符直接實例化對象。這使得程序在判斷針對某個給定實例須要建立哪些對象時更加靈活。設計模式

工廠模式（Factory Pattern）

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)
java.util.EnumSet#of()
javax.xml.bind.JAXBContext#createMarshaller() and other similar methods

抽象工廠模式（Abstract Factory Pattern）

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

單例模式（Singleton Pattern）

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

建造者模式（Builder Pattern）

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()

原型模式（Prototype Pattern）

java.lang.Object#clone()

結構型模式

這些設計模式關注類和對象的組合。繼承的概念被用來組合接口和定義組合對象得到新功能的方式app

適配器模式（Adapter Pattern）

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

橋接模式（Bridge Pattern）

TODOide

過濾器模式（Filter、Criteria Pattern）

組合模式（Composite Pattern）

java.awt.Container#add(Component)
javax.faces.component.UIComponent#getChildren()

裝飾器模式（Decorator Pattern）

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

外觀模式（Facade Pattern）

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.

享元模式（Flyweight Pattern）

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

代理模式（Proxy Pattern）

java.lang.reflect.Proxy
java.rmi.*
javax.ejb.EJB (explanation here)
javax.inject.Inject (explanation here)
javax.persistence.PersistenceContext

行爲型模式

責任鏈模式（Chain of Responsibility Pattern）

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

命令模式（Command Pattern）

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

解釋器模式（Interpreter Pattern）

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

迭代器模式（Iterator Pattern）

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

中介者模式（Mediator Pattern）

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()

備忘錄模式（Memento Pattern）

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

觀察者模式（Observer Pattern）

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

狀態模式（State Pattern）

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

空對象模式（Null Object Pattern）

TODO學習

策略模式（Strategy Pattern）

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()

模板模式（Template Pattern）

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.