Spring Boot集成MapStruct报错：找不到UserMapper类型Bean

我是Spring Boot新手，遇到了Bean找不到的问题。

相关代码 #

UserService #

@RequiredArgsConstructor 
@Service
public class UserService {
    
    private final UserRepository userRepository;

    private final UserMapper userMapper;

    public UserDto login(CredentialDto credentialDto) {
        User user = userRepository.findBylogin(credentialDto.login())
            .orElseThrow(() -> {
            ApplicationException ex = new ApplicationException();
            ex.setMessage("Unknown user");
            return ex;
        });
        return userMapper.toUserDto(user);
    }
}

UserMapper #

@Mapper(componentModel = "spring")
public interface UserMapper {
    UserDto toUserDto(User user);
}

报错信息 #

描述：
Parameter 1 of constructor in com.example.jwttest.service.UserService required a bean of type 'com.example.jwttest.mappers.UserMapper' that could not be found.

操作建议：
Consider defining a bean of type 'com.example.jwttest.mappers.UserMapper' in your configuration.

• 检查MapStruct依赖是否完整引入
  确保项目构建文件（Maven的pom.xml或Gradle的build.gradle）包含MapStruct核心依赖和注解处理器。以Maven为例：

  <dependencies>
      <dependency>
          <groupId>org.mapstruct</groupId>
          <artifactId>mapstruct</artifactId>
          <version>1.5.5.Final</version> <!-- 使用最新稳定版 -->
      </dependency>
  </dependencies>
  
  <build>
      <plugins>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-compiler-plugin</artifactId>
              <version>3.8.1</version>
              <configuration>
                  <source>17</source> <!-- 匹配你的JDK版本 -->
                  <target>17</target>
                  <annotationProcessorPaths>
                      <path>
                          <groupId>org.mapstruct</groupId>
                          <artifactId>mapstruct-processor</artifactId>
                          <version>1.5.5.Final</version>
                      </path>
                      <!-- 如果使用Lombok，需添加以下依赖 -->
                      <path>
                          <groupId>org.projectlombok</groupId>
                          <artifactId>lombok</artifactId>
                          <version>1.18.30</version>
                      </path>
                      <path>
                          <groupId>org.projectlombok</groupId>
                          <artifactId>lombok-mapstruct-binding</artifactId>
                          <version>0.2.0</version>
                      </path>
                  </annotationProcessorPaths>
              </configuration>
          </plugin>
      </plugins>
  </build>
  

• 确保Spring能扫描到Mapper接口
  如果UserMapper所在包不在Spring Boot启动类的同级或子包下，需要在启动类添加@MapperScan指定Mapper包路径：

  @SpringBootApplication
  @MapperScan("com.example.jwttest.mappers") // 替换为你的Mapper实际包路径
  public class JwtTestApplication {
      public static void main(String[] args) {
          SpringApplication.run(JwtTestApplication.class, args);
      }
  }
  

• 重新编译项目
  MapStruct是编译时生成代理类，修改依赖或配置后执行mvn clean compile（Maven）或gradle clean build（Gradle），确保生成了UserMapperImpl实现类。

• 验证Mapper注解正确性
  确认@Mapper注解来自org.mapstruct.Mapper包，避免引用其他同名注解。

内容的提问来源于stack exchange，提问作者Ali Raza