java设计模式之代理模式（8）

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代理模式就是，不直接调用目标函数，而是通过一个代理类来调用。

它的类继承关系和装饰模式很类似。但是它们的目的不一样。

代理模式不会增加新的功能，只是在调用和被调用之间加入代理层。而装饰模式旨在增加新功能。

看代码：

package com.pattern.struct.proxy;public interface Subject {public void request();}

package com.pattern.struct.proxy;public class RealSubject implements Subject {@Overridepublic void request() {System.out.println("-------------a");}}

package com.pattern.struct.proxy;public class SubjectProxy implements Subject{private Subject subject;public SubjectProxy(Subject subject){this.subject = subject;}@Overridepublic void request() {doBefor();this.subject.request();doAfter();}private void doBefor(){System.out.println("-----------before------------");}private void doAfter(){System.out.println("-----------after------------");}}

package com.pattern.struct.proxy;public class StartUp {public static void main(String...args){Subject subject = new RealSubject();Subject proxy = new SubjectProxy(subject);proxy.request();}}

java内置了动态代理，常见的AOP事务处理就是使用动态代理实现的。

package com.pattern.struct.proxy.dynamic;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import com.pattern.struct.proxy.Subject;public class SubjectHandler implements InvocationHandler{private Subject subject;public SubjectHandler(Subject subject){this.subject = subject;}@Overridepublic Object invoke(Object obj, Method method, Object[] aobj)throws Throwable {System.out.println("do before...");method.invoke(subject, aobj);System.out.println("do after...");return null;}}

package com.pattern.struct.proxy.dynamic;import java.lang.reflect.Proxy;import com.pattern.struct.proxy.RealSubject;import com.pattern.struct.proxy.Subject;public class StartUp {public static void main(String[] args) {RealSubject realSubject = new RealSubject();Subject subject = (Subject) Proxy.newProxyInstance(realSubject.getClass().getClassLoader(), realSubject.getClass().getInterfaces(), new SubjectHandler(realSubject));subject.request();}}

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