无法自动装配字段spring-boot

Question

需要帮忙，我刚开始学习Spring，但似乎无法找到问题所在：

Application.java - 没有包

@Configuration
//@ComponentScan({"com.mapping","com.accesors","com.controllers"}) --Originaly tried this
@ComponentScan(basePackageClasses={UserDAO.class,Root.class,User.class})
@EnableAutoConfiguration
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

User.java - 包 com.mapping

@Entity
public class User {

    @Id
    @GeneratedValue
    private Long id;
    private String userName;
    private String password;
    //accesors
}

UserDAO.java - 包com.accesors

@Repository
public interface UserDAO extends JpaRepository<User, Long> {

}

Root.java - 包 com.controllers

@Controller
@RequestMapping("/*")
public class Root {

    @Autowired
    UserDAO userDAO;

    @RequestMapping("/")
    @ResponseBody
    public String rootAction(@RequestParam(defaultValue="foo") String name){
        List<User> lst = this.userDAO.findAll();
        for(User u : lst){
            System.out.println(u);
        }
        return "hello, " + name;
    }

}

当我运行这个项目时，似乎出现了以下异常：

堆栈跟踪：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'root': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.accesors.UserDAO com.controllers.Root.userDAO; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.accesors.UserDAO] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:292)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1185)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:475)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:298)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:703)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:760)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:482)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:120)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:691)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:320)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:952)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:941)
    at demo.Application.main(Application.java:14)

据我了解，这意味着@ComponentScan未检测到包。

- Ricardo Garza V.

---

那么是谁实现了UserDao？ - Makoto

@Makoto 没有什么，这是Spring-Data-JPA，请参考http://www.petrikainulainen.net/spring-data-jpa-tutorial/。 - Scary Wombat

如果我没记错的话，Spring-Data-JPA使用切面来在运行时创建类。 - Scary Wombat

Answer 1

如果您的Spring Data存储库不在@EnableAutoConfiguration类的子包中，则需要添加@EnableJpaRepositories（如果实体不在子包中，则同样适用于@EntityScan）。

- Dave Syer

---

这太棒了。我最初认为在@componentScan中包含包就可以解决问题。 但似乎你必须分别在@EnableJpaRepositories和@EntityScan中包含基础包之外的存储库和实体。谢谢。 - Mukul Goel

Answer 2

如果您正在使用SpringRunner测试您的SpringBoot应用程序，请不要忘记包含ComponentScan注释。

@RunWith(SpringRunner.class)    
@SpringBootTest (classes = YourRestController.class )    
@ComponentScan({"your package goes here"})    
@AutoConfigureMockMvc    
@ActiveProfiles("development")    
public class Foo{
}

- Antonio Martin