java 简单的动态代理例子

package util;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
import java.lang.reflect.Method;
//抽象角色：java动态代理的实现目前只支持接口，不支持抽象类
interface BusinessFoo
{
    void foo();
}
interface BusinessBar
{
   String bar(String message);
}
//真实角色：真正实现业务逻辑方法
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;
   }
}
//动态角色：动态生成代理类
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));
   }
}
//测试类
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);
   }
}