SpringBoot 3.2.2 @Autowired注入DeptMapper失败，2.7.5版本正常

错误信息 #

***************************
APPLICATION FAILED TO START
***************************

Description:

Field deptMapper in com.itheima.service.impl.DeptServiceImpl required a bean of type 'com.itheima.mapper.DeptMapper' 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.itheima.mapper.DeptMapper' in your configuration.

问题背景 #

使用SpringBoot 3.2.2启动项目时出现上述错误，但将pom.xml中SpringBoot版本改回2.7.5后，无需修改任何代码即可正常启动。项目结构符合SpringBoot路径规范。

相关代码 #

Controller层 #

package com.itheima.controller;

import com.itheima.pojo.Dept;
import com.itheima.pojo.Result;
import com.itheima.service.DeptService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@Slf4j
@RestController
public class DeptController {
    @Autowired(required = true)
    private DeptService deptService;

    @GetMapping("/depts")
    public Result list() {
        log.info("search all departments");
        List<Dept> deptList = deptService.list();
        return Result.success(deptList);
    }
}

Service接口 #

package com.itheima.service;

import com.itheima.pojo.Dept;

import java.util.List;

public interface DeptService {
    /*search all departments*/
    List<Dept> list();
}

Service实现类 #

package com.itheima.service.impl;

import com.itheima.mapper.DeptMapper;
import com.itheima.pojo.Dept;
import com.itheima.service.DeptService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class DeptServiceImpl implements DeptService {
    @Autowired
    private DeptMapper deptMapper;

    @Override
    public List<Dept> list() {
        return deptMapper.list();
    }
}

MyBatis Mapper接口 #

package com.itheima.mapper;

import com.itheima.pojo.Dept;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;

import java.util.List;

@Mapper
public interface DeptMapper {
    // 查询全部的部门数据
    @Select("select * from dept")
    List<Dept> list();
}

POJO类 #

package com.itheima.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.time.LocalDateTime;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Dept {
    private Integer id;
    private String name;
    private LocalDateTime createTime;
    private LocalDateTime updateTime;
}

原因分析与解决方案 #

SpringBoot 3.x基于Spring Framework 6.x，对依赖版本有严格的兼容性要求：

• MyBatis Starter版本适配问题：SpringBoot 3.2.2需要搭配MyBatis Spring Boot Starter 3.0.x及以上版本，而SpringBoot 2.7.5对应的是MyBatis Starter 2.x版本。如果pom.xml中MyBatis Starter版本未同步升级，会导致MyBatis无法正常扫描@Mapper注解生成Bean。
• 包扫描范围问题：虽然项目结构符合规范，但SpringBoot 3.x在自动配置的扫描逻辑上有细微调整，可尝试在启动类上添加@MapperScan("com.itheima.mapper")注解，强制指定Mapper接口的扫描路径，确保MyBatis能识别并生成代理Bean。

具体解决步骤 #

步骤1：升级MyBatis Starter版本

在pom.xml中确保MyBatis Spring Boot Starter版本与SpringBoot 3.2.2兼容，例如：

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>3.0.3</version> <!-- 适配SpringBoot 3.x的版本 -->
</dependency>

步骤2：添加@MapperScan注解到启动类

在SpringBoot启动类上添加@MapperScan注解，指定Mapper所在的包：

package com.itheima;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.itheima.mapper") // 指定Mapper接口所在包
public class YourApplication {
    public static void main(String[] args) {
        SpringApplication.run(YourApplication.class, args);
    }
}

步骤3：检查JDK版本

SpringBoot 3.x要求JDK 17及以上版本，确保项目运行环境是JDK 17+，否则也可能导致依赖加载异常。

内容的提问来源于stack exchange，提问作者lilpiggie0522