org.springframework.beans.factory.BeanNotOfRequiredTypeException错误

错误信息：org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.dbzhang.demo3.Demo3': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'userDao' must be of type [com.dbzhang.demo3.UserDaoImpl], but was actually of type [com.sun.proxy.$Proxy12]

错误代码：

package com.dbzhang.demo3;

import javax.annotation.Resource;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext3.xml")
public class Demo3 {
    
    @Resource(name="userDao")
    private UserDaoImpl userDao;
    @Test
    public void run(){
        userDao.save();
    }
}

出现这种情况的原因：当使用annotation方式注入spring的bean的时候出现的，这里的spring代理机制采用的是JDK动态代理机制，

其中JDK动态代理机制，只能实现对接口的注入，不能实现类的注入，而UserDaoImpl是一个实现类，不能采用JDK动态代理机制；因此需要改正：

package com.dbzhang.demo3;

import javax.annotation.Resource;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext3.xml")
public class Demo3 {
    
    @Resource(name="userDao")
    private UserDao userDao;
    @Test
    public void run(){
        userDao.save();
    }
}

可以参看如下文章：https://blog.csdn.net/jyp360/article/details/70215002

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