代理模式

一． 静态代理
1． Subject.java

package com.test;

public abstract class Subject {
	public abstract void request();
}

2． RealSubject.java

package com.test;

public class RealSubject extends Subject {

	@Override
	public void request() {
		System.out.println("real subject");
	}

}

3． ProxySubject.java

package com.test;

public class ProxySubject extends Subject {

	private RealSubject realSubject;
	
	@Override
	public void request() {
		this.PreRequest();
		if(realSubject==null){
			realSubject=new RealSubject();
		}
		realSubject.request();
		this.PostRequest();
	}
	
	private void PreRequest(){
		System.out.println("pre request");
	}
	
	private void PostRequest(){
		System.out.println("post request");
	}

}

4． Client.java

package com.test; 

public class Client {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Subject proxy=new ProxySubject();
		proxy.request();
	}

}

二． 动态代理
1. Subject.java

package com.test.dynamicproxy;

public interface Subject {
	public void request();
}

2. RealSubject.java

package com.test.dynamicproxy;

public class RealSubject implements Subject {

	@Override
	public void request() {
		System.out.println("from real subject");
	}

}

3. ProxySubject.java

package com.test.dynamicproxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

public class ProxySubject implements InvocationHandler {
	
	private Object object;
	
	public ProxySubject(Object object){
		this.object=object;
	}

	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		System.out.println("pre process");
		method.invoke(object, args);
		System.out.println("post process");
		return null;
	}

}

4. Client.java

package com.test.dynamicproxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;

public class Client {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		
		RealSubject realSubject=new RealSubject();
		
		InvocationHandler handler=new ProxySubject(realSubject);
		
		Class<?> clz=realSubject.getClass();
		
		Subject subject=(Subject)Proxy.newProxyInstance(clz.getClassLoader(), clz.getInterfaces(), handler);
		
		subject.request();
	}

}