aop实现

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();
    }