public interface UserDao {    void save();}public class UserDaoImpl implements UserDao {    private String name;        public void save() {        System.out.println("save() is called, name: "+name);    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    }

package com.maple.util;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import com.maple.dao.UserDao;import com.maple.dao.impl.UserDaoImpl;public class ProxyFactory implements InvocationHandler {    private Object target;        public Object createUserDao(Object target){        this.target=target;        return Proxy.newProxyInstance(this.target.getClass().getClassLoader(),                        this.target.getClass().getInterfaces(), this);    }    @Override    public Object invoke(Object proxy, Method method, Object[] args)            throws Throwable {        System.out.println(proxy.getClass().getName());        Object result=null;        UserDaoImpl userDao=(UserDaoImpl)this.target;        if(userDao.getName()!=null){            result=method.invoke(userDao, args);        }else{            System.out.println("the name is null");        }        return result;    }}

@Test    public void test() {        ProxyFactory pf=new ProxyFactory();        UserDaoImpl u=new UserDaoImpl();        u.setName("maple");        UserDao userDao=(UserDao) pf.createUserDao(u);        userDao.save();    }