Proxy动态代理

　　　　Proxy动态代理

package com.test.dynamicproxy;

public interface Subject {

    public void request();
}

package com.test.dynamicproxy;

public class RealSubject implements Subject {

    @Override
    public void request() {
        System.out.println("request() from RealSubject");

    }

}

package com.test.dynamicproxy;

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

public class SubjectInvocationHandler implements InvocationHandler {

    private Object object;
    
    public SubjectInvocationHandler(Object obj) {
        this.object = obj;
    }
    
    @Override
    public Object invoke(Object proxy, Method method, Object[] args)
            throws Throwable {
        method.invoke(object,args);
        return null;
    }

}

package com.test.dynamicproxy;

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

public class Client {
    
    public static void main(String[] args) {
        
        RealSubject real = new RealSubject();
        InvocationHandler ih = new SubjectInvocationHandler(real);
        Class<?> clazz = real.getClass();
        Subject s = (Subject)Proxy.newProxyInstance(clazz.getClassLoader(),clazz.getInterfaces(),ih);
        
        s.request();        //request() from RealSubject
                
        System.out.println(s.getClass().getName());        //$Proxy0
        System.out.println(s instanceof Proxy);        //true
        
        for(Class interf : s.getClass().getInterfaces()){
            System.out.println(interf.getName());        //com.test.dynamicproxy.Subject
        }
        
        
//        System.out.println(s.getClass().getPackage());         //null
//        System.out.println(s.getClass().getSuperclass());    //class java.lang.reflect.Proxy
//        System.out.println(Proxy.class.getPackage());     //package java.lang.reflect, Java Platform API Specification, version 1.6
    }

}

Object java.lang.reflect.Proxy.newProxyInstance(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h) throws IllegalArgumentException

Returns an instance of a proxy class for the specified interfaces that dispatches method invocations to the specified invocation handler. This method is equivalent to:

     Proxy.getProxyClass(loader, interfaces).
         getConstructor(new Class[] { InvocationHandler.class }).
         newInstance(new Object[] { handler });
 

Proxy.newProxyInstance throws IllegalArgumentException for the same reasons that Proxy.getProxyClass does.

Parameters:

loader the class loader to define the proxy class

interfaces the list of interfaces for the proxy class to implement

h the invocation handler to dispatch method invocations to

Returns:

a proxy instance with the specified invocation handler of a proxy class that is defined by the specified class loader and that implements the specified interfaces

Throws:

IllegalArgumentException - if any of the restrictions on the parameters that may be passed to getProxyClass are violated

NullPointerException - if the interfaces array argument or any of its elements are null, or

Client 中   s   extends Proxy implements Subject

s.request() 方法调用流程 ：

s 是 Subject 的 implementation  .s.request() 的实现

s 伪代码：

s extends Proxy implements Subject{

　　InvocationHandler ih;

　　......

　　public void request(){

　　　　ih.invoke(....);

　　}

}