springboot整合mybatis，mapper映射错误

最近学习springboot的整合mybatis中
遇到mapper不能注入成功，在网上上找了2天， 也没能解决

我自己关注过的信息有：

  1. 注意目录结构，所有代码要放到DemoApplication类的同级或者下级目录
  2. StudentMapper.xml文件放到resources， 或者跟StudentMapper.java （interface文件）同一个目录
    先弄一个错误案例供分析，此案例是把mapper的xml放到resources目录中的
    求各位解惑，感谢了

以下是报告错误：

Description:

Field studentMapper in com.example.demo.service.imp.StudentServiceImpl required a bean of type 'com.example.demo.mapper.StudentMapper' that could not be found.

The injection point has the following annotations:
    - @org.springframework.beans.factory.annotation.Autowired(required=true)


Action:

Consider defining a bean of type 'com.example.demo.mapper.StudentMapper' in your configuration.

主要参照一下两篇文章：
SpringBoot框架：https://blog.csdn.net/friggly/article/details/123888590
Mybatis之逆向工程生成代码（简单容易上手）： https://blog.csdn.net/xiaoheihai666/article/details/125664202
利用逆向生成代码之后，目录结构如图：

img

application.properties 文件内容：

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/testdb
spring.datasource.username=root
spring.datasource.password=123456
mybatis.mapper-locations=classpath:mapper/*.xml

StudentServiceImpl.java 文件如下:

package com.example.demo.service.imp;

import com.example.demo.mapper.StudentMapper;
import com.example.demo.model.Student;
import com.example.demo.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class StudentServiceImpl implements StudentService {
    @Autowired
    private StudentMapper studentMapper;

    @Override
    public Student queryStudentById(Integer id) {
        return null;
    }
}

StudentMapper.java 文件内容：

package com.example.demo.mapper;

import com.example.demo.model.Student;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface StudentMapper {
    int deleteByPrimaryKey(Integer id);

    int insert(Student record);

    int insertSelective(Student record);

    Student selectByPrimaryKey(Integer id);

    int updateByPrimaryKeySelective(Student record);

    int updateByPrimaryKey(Student record);
}

StudentMapper.xml的截图：

img

答应我，下次咱们搞个压缩包丢网盘，别搞代码片段了，好吗