proxy代理模式

	package proxy;
	import java.lang.reflect.InvocationHandler;
	import java.lang.reflect.Method;
	import java.lang.reflect.Proxy;
	class Logic{
	public void logic(){
	Dao dao = Factory.create();
	System.out.println("dynamic proxy's name: "+dao.getClass().getName());
	dao.insert();
	}
	}
	class Factory{
	static Dao create(){
	Dao dao = new JdbcDao();
	MyInvocationHandler hand = new MyInvocationHandler();
	return (Dao)hand.get(dao);
	}
	}
	interface Dao{
	public void update();
	public void insert();
	}
	class JdbcDao implements Dao{
	public void update(){
	System.out.println("in jdbc update");
	}
	public void insert(){
	System.out.println("in jdbc insert");
	}
	}
	class HibernateDao implements Dao{
	public void update(){
	System.out.println("in hibernate update");
	}
	public void insert(){
	System.out.println("in hibernate insert");
	}
	}
	class MyInvocationHandler implements InvocationHandler {
	Object o;
	public Object get(Object o){
	System.out.println("in get method of MyInvocationHandler");
	this.o = o;
	return Proxy.newProxyInstance(o.getClass().getClassLoader(),o.getClass().getInterfaces(),this);
	}
	public Object invoke(Object arg0, Method arg1, Object[] arg2)
	throws Throwable {
	System.out.println("write log before invoke");
	Object result = arg1.invoke(o, arg2);
	System.out.println("write log after invoke");
	return result;
	}
	}
	public class Test {
	public static void main(String[] args) {
	Logic l = new Logic();
	l.logic();
	}
	}

 真么发现代理模式那里好  为什么还要用代理模式  

 

     为什么不写一个类  在类中写一个 方法 里面传一个class类型 用那个类就调用哪个类不就得啦         有知道的还请详解啊