interface Business 
{ 
    void doAction(); 
}
 

class BusinessImplProxy implements Business 
{ 
    private BusinessImpl bi; 
    public void doAction() 
    { 
        if (bi==null) 
        { 
            bi = new BusinessImpl(); 
        } 
        doBefore(); 
        bi.doAction(); 
        doAfter(); 
    } 
    public void doBefore() 
    { 
        System.out.println("前置處理！"); 
    } 
    public void doAfter() 
    { 
        System.out.println("后置處理！"); 
    } 
} 
//測試類 
class Test 
{ 
    public static void main(String[] args) 
    { 
        //引用變量定義為抽象角色類型 
        Business bi = new BusinessImplProxy(); 
        bi.doAction(); 
    } 
}

<span></span>

import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.Proxy;
 import java.lang.reflect.Method;
 //抽象角色：java動態(tài)代理的實現(xiàn)目前只支持接口，不支持抽象類
 interface BusinessFoo
 {
     void foo();
 }
 interface BusinessBar
{
    String bar(String message);
}
//真實角色：真正實現(xiàn)業(yè)務(wù)邏輯方法
class BusinessFooImpl implements BusinessFoo
{
    public void foo()
    {
        System.out.println("BusinessFooImpl.foo()");
    }
}
class BusinessBarImpl implements BusinessBar
{
    public String bar(String message)
    {
        System.out.println("BusinessBarImpl.bar()");
        return message;
    }
}
//動態(tài)角色：動態(tài)生成代理類
class BusinessImplProxy implements InvocationHandler
{
    private Object obj;
    BusinessImplProxy() {
    }
    BusinessImplProxy(Object obj) {
        this.obj = obj;
    }
    public Object invoke(Object proxy,Method method,Object[] args) throws Throwable
    {
        Object result = null;
        doBefore();
        result = method.invoke(obj,args);
        doAfter();
        return result;
    }
    public void doBefore(){
        System.out.println("do something before Business Logic");
    }
    public void doAfter(){
        System.out.println("do something after Business Logic");
    }
    public static Object factory(Object obj)
    {
        Class cls = obj.getClass();
        return Proxy.newProxyInstance(cls.getClassLoader(),cls.getInterfaces(),new BusinessImplProxy(obj));
    }
}
//測試類
public class DynamicProxy
{   
    public static void main(String[] args) throws Throwable
    {
        BusinessFooImpl bfoo = new BusinessFooImpl();
        BusinessFoo bf = (BusinessFoo)BusinessImplProxy.factory(bfoo);
        bf.foo();
        System.out.println();

        BusinessBarImpl bbar = new BusinessBarImpl();
        BusinessBar bb = (BusinessBar)BusinessImplProxy.factory(bbar);
        String message = bb.bar("Hello,World");
        System.out.println(message);
    }
}