代理模式+拦截器

public interface MyTargetInterface {
	public void sayHello();
}

public class MyTarget implements MyTargetInterface {
	public void sayHello() {
		System.out.println("welcome to the struts world!");
	}
}

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

public class MyHandler implements InvocationHandler {
	
	private Object obj;
	
	public void setObj(Object obj) {
		this.obj = obj;
	}

	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		
		System.out.println("before invoke the method...");
		method.invoke(obj, args);
		System.out.println("after invoke the method...");

		return null;
	}

}

import java.lang.reflect.*;

public class MyProxy {
	public Object getMyProxy(Object obj,InvocationHandler target) {
		return Proxy.newProxyInstance(obj.getClass().getClassLoader(),
				obj.getClass().getInterfaces(), target);
	}
}

public class Client {

	public static void main(String[] args) {
		MyTargetInterface mytarget = new MyTarget();
		MyHandler myhandler = new MyHandler();
		myhandler.setObj(mytarget);
		MyProxy myproxy = new MyProxy();		
		MyTargetInterface proxy = (MyTargetInterface)myproxy.getMyProxy(mytarget, myhandler);
		proxy.sayHello();
	}

}