SpringBoot启动报错“Consider defining a bean of type ‘xxx.mapper.UserMapper‘ in your configuration.“

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SpringBoot启动报错“Consider defining a bean of type ‘xxx.mapper.UserMapper‘ in your configuration.“

异常

启动SpringBoot项目报错：

2021-06-25 15:32:39.540 WARN 23108 --- [ main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userController': Unsatisfied dependency expressed through field 'userMapper'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.example.demo.mapper.UserMapper' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} 2021-06-25 15:32:39.541 INFO 23108 --- [ main] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} closing ... 2021-06-25 15:32:39.548 INFO 23108 --- [ main] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} closed 2021-06-25 15:32:39.552 INFO 23108 --- [ main] o.apache.catalina.core.StandardService : Stopping service [Tomcat] 2021-06-25 15:32:39.569 INFO 23108 --- [ main] ConditionEvaluationReportLoggingListener : Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled. 2021-06-25 15:32:39.606 ERROR 23108 --- [ main] o.s.b.d.LoggingFailureAnalysisReporter : *************************** APPLICATION FAILED TO START *************************** Description: Field userMapper in com.example.demo.controller.UserController required a bean of type 'com.example.demo.mapper.UserMapper' 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.UserMapper' in your configuration. 错误代码

UserMapper.java

@Mapper public interface UserMapper { @Select("select * from user where username=#{username}") User selectByUsername(String username); }

这里没有service层，是直接在controller层调用的Mapper类中的方法，所以UserController.java

@Controller public class UserController { @Autowired private UserMapper userMapper; @GetMapping("/mybatis") public String table(String username,Model model){ System.out.println(username); User user = userMapper.selectByUsername(username); System.out.println(user); model.addAttribute("users",new ArrayList<>().add(user)); return "table"; } }

DemoApplication.java

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

application.properties

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

上面的代码为什么要把主启动类DemoApplication和配置文件application.properties的代码拿出来说呢？

因为这是SpringBoot整合Mybatis的代码，所以在Mapper接口类使用的是@Mapper注解。

但如果每个Mapper接口类都添加@Mapper注解比较麻烦，所以用了@MapperScan注解批量扫描Mapper接口类。

可以说冲突了，但事实上并不是，真正的原因是我@MapperScan中的值的路径写错了：

解决

只选择一种注解方式，要么使用@Mapper，要么使用@MapperScan注解，不能都使用。

经过测试，两种方式都能够一起使用，但是使用的时候@MapperScan的属性值（即Mapper接口类所在的路径）一定要正确，否则一定会报错，所以建议只使用一种方式。

只使用@MapperScan

只使用@Mapper

@MapperScan和@Mapper注解一起使用

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