public interface MethodDao { 
   public void sayHello(); 
}

public class MethodImpl implements MethodDao { 
  public void sayHello() 
  { 
    System.out.println("hello world"); 
  } 
}

public class DynamicProxy implements InvocationHandler {
 private Object object;
 /**
 
 * <p>Title: </p>
 * <p>Description: </p>
 * 接受被代理类
 */
 public DynamicProxy(Object object) {
  this.object=object;
  // TODO Auto-generated constructor stub
 }
 /* (non-Javadoc)
  * @see java.lang.reflect.InvocationHandler#invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
  *实现invoke方法,在方法执行之后添加操作
  */
 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
  // TODO Auto-generated method stub
  System.out.println("=====方法执行前=======");
  method.invoke(object, args);
  System.out.println("=====方法执行后=======");
  return null;
 }
}

public class Test { 
  public static void main(String[] args) { 
     MethodDao methodDao=new MethodImpl(); 
     InvocationHandler handler = new DynamicProxy(methodDao); 
     //第一个参数是类加载器，与handler相同; 
     //第二个是参数对象实现的接口,如果没有的话需要使用cdlib 
     //第三个参数是InvocationHandler. 
     //该类返回的其实是MethodImpl类 
     methodDao=(MethodDao) Proxy.newProxyInstance(handler.getClass().getClassLoader(), methodDao.getClass().getInterfaces(), handler); 
     methodDao.sayHello(); 
  } 
   
   
}