Java设计模式(14)--代理

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

 

How to
Proxy
maintains a reference that lets the proxy access the real subject
provides an interface identical to Subject's

Subject
defines the common interface for RealSubject and Proxy

RealSubject
defines the real object that the proxy represents

Known case
delay initialization
asyn call
remote proxy (RMI)
security validation
cache

 

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 } }