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Intent

Provide a surrogate or placeholder for another object to control access to it.

 

How to

Proxymaintains a reference that lets the proxy access the real subjectprovides an interface identical to Subject's

Subjectdefines the common interface for RealSubject and Proxy

RealSubjectdefines the real object that the proxy represents

Known casedelay initializationasyn callremote proxy (RMI)security validationcache

 

UML

 

样例代码

package org.haha.DesignPatterns.proxy;public class Client { public static void main(String[] args) { Subject subject = new Proxy(); //after long time subject.request(); } }package org.haha.DesignPatterns.proxy;public interface Subject { void request(); }package org.haha.DesignPatterns.proxy;public class Proxy implements Subject { private Subject realSubject; public Proxy() { } public void request() { if (realSubject == null) { realSubject = new RealSubject(); } realSubject.request(); }}package org.haha.DesignPatterns.proxy;public class RealSubject implements Subject { public RealSubject() { //heavyweight initialization } public void request() { //do something }}

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