一   导入依赖

       <!--整合mybatis-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.3</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.21</version>
        </dependency>
         <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

二    编写配置文件

appliction.yml中添加如下配置

	spring:
	  datasource:
	    url: jdbc:mysql://127.0.0.1:3306/mydb?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai
	    driver-class-name: com.mysql.cj.jdbc.Driver
	    username: root
	    password: root
	mybatis:
	  mapper-locations: classpath:mybatis/*.xml
	  type-aliases-package: com.msb.pojo

mapper-locations: classpath:mybatis/*.xml  mapper映射文件包扫描

type-aliases-package:实体类别名包扫描

三   编写功能代码

1.在启动类上添加注解@MapperScan("com.msb.mapper")，表示mapper接口所在位置

	@SpringBootApplication
	@MapperScan("com.msb.mapper")
	public class MyApplication {
	    public static void main(String[] args) {
	        SpringApplication.run(MyApplication.class,args);
	    }
	

2 .定义mapper接口

如果不在MyApplication启动类上添加@MapperScan必须在UserMapper接口上添加@Mapper注解。

	//@Mapper
	public interface UserMapper {
	    List<User> selectAll();
	}

3 定义mapper.xml映射文件

在resource下新建mybatis文件夹，mapper.xml文件名没有要求了，不需要和接口名完全对应了，是根据namespace去找接口。但是最好还是和接口名字保持一致

 4 .controller层代码

	@Controller
	@RequestMapping("/user")
	public class UserController {
	
    @Autowired
	    private UserService userService;
	
	    @RequestMapping("/findAll")
	    @ResponseBody
	    public List<User> findAll(){
        return userService.findAll();
    }
	
	}

 5.service层代码

	@Service
	public class UserServiceImpl implements UserService {
	
	    @Autowired
	    private UserMapper userMapper;
	    @Override
	    public List<User> findAll() {
	        return userMapper.findAll();
	    }
	}

6. idea中往往会误报代码错误,如果我们确定代码无问题,可以通过降低idea检查代码的严格程度来消除报错

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