java - 没有找到类型匹配的 bean ... 来进行依赖...预计至少有 1 个有资格作为 Autowiring 候选者的 bean

Question

这个问题已经被回答过好几次了，但我已经设置了所有注释，并且它似乎已正确连接。

用户服务接口(interface):

public interface UserService {

    User findUserById(Long id);
    User findUserByName(String name);
    List<User> findAllUsers();
    void saveUser(User user);
    void updateUser(User user);
    void deleteUserById(long id);
    void deleteAllUsers();
    public boolean isUserExist(User user);
}

用户服务Impl

@Service
@Transactional
public class UserServiceImpl implements UserService {

    private static final AtomicLong counter = new AtomicLong();

    private static List<User> users;

    static {
        users = populateDummyUsers();
    }

    @Override
    public User findUserById(Long id) {

        for (User user : users) {
            if (user.getId() == id) {
                return user;
            }
        }

        return null;
    }

    @Override
    public User findUserByName(String name) {
        for (User user : users) {
            if (user.getUsername().equalsIgnoreCase(name)) {
                return user;
            }
        }
        return null;
    }

失败的测试用例:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = SpringCrudApplication.class)
@ComponentScan("com.service")
public class ServiceTest {


    private UserService userService;

    @Autowired
    public void setUserService(UserService userService) {
        this.userService = userService;
    }

    @Test
    public void findUserByIdTest() throws Exception {

        long id = (long) 0;
        User userTest = new User(id,"Mike","644 Main St", "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="a8c9d8d8c4cde8cfc5c9c1c486cbc7c5" rel="noreferrer noopener nofollow">[email protected]</a>");

        User user = userService.findUserById(id);

        assert user.getAddress() != null;
        assert user.getEmail() != null;
        assert user.getUsername() != null;

    }

我尝试在 com.service 和 com.serviceImpl 的测试类中使用 componentScan，但没有成功。

完整错误:

org.springframework.beans.factory.UnsatisfiedDependencyException:   
Error creating bean with name 'com.service.test.ServiceTest': 
Unsatisfied dependency expressed through method 'setUserService' 
parameter 0: No qualifying bean of type [com.service.UserService] 
found for dependency [com.service.UserService]: expected at least 1 
bean which qualifies as autowire candidate for this dependency. 
Dependency annotations: {}; nested exception is 
org.springframework.beans.factory.NoSuchBeanDefinitionException: No 
qualifying bean of type [com.service.UserService] found for 
dependency [com.service.UserService]: expected at least 1 bean which 
qualifies as autowire candidate for this dependency. Dependency 
annotations: {}

--------------------解决方案--------------------------------

我必须将 @ComponentScan 添加到主方法中:

@SpringBootApplication
@ComponentScan("com.serviceImpl, com.service")
public class SpringCrudApplication {

    public static void main(String[] args) {

        SpringApplication.run(SpringCrudApplication.class, args);
    }
}

Answer 1

ComnponentScan 必须找到实现，而不是接口(interface)。 因此，如果您的类 UserServiceImpl 位于包 com.serviceImpl 中，则必须扫描此包。

包名看起来很奇怪，包名只能是小写。 因此，请尝试将包重命名为 com.service.impl 并进行扫描。

因为您使用的是@Transactional，所以spring将创建一个实现UserService的代理。所以你只能注入(inject)UserService而不能注入(inject)UserServiceImpl。 检查您的代码，可能您正在尝试在其他地方@Autowire UserServiceImpl。

除了你的异常“没有匹配的类型的bean..”之外，堆栈跟踪中通常还会有一条类似“无法 Autowiring ”的消息，它准确地说明了， spring 尝试在哪里注入(inject)什么类型。