Spring Boot启动失败--在配置中定义类型为“TopicRepository”的bean

Question

我一直在学习Spring Boot的JavaBrains教程。

我的项目结构如下：

courseapiapp.java：

@SpringBootApplication
@ComponentScan(basePackages = {
    "com.bloodynacho.rishab.topics"
})
@EntityScan("com.bloodynacho.rishab.topics")
public class CourseApiApp {

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

@RestController
public class TopicController {

    @Autowired
    private TopicService topicService;

    @RequestMapping(
        value = "/topics"
    )
    public List<Topic> getAllTopcs() {
        return topicService.getAllTopics();
    }
}

@Service
public class TopicService {

    @Autowired
    private TopicRepository topicRepository;

    public List<Topic> getAllTopics() {
        List<Topic> topics = new ArrayList<>();
        this.topicRepository
            .findAll()
            .forEach(topics::add);
        return topics;
    }
}

topic.java：

@Entity
public class Topic {
    @Id
    private String id;
    private String name;
    private String description;
}

topicrepository.java：

@Repository
public interface TopicRepository extends CrudRepository<Topic, String>{
}

pom.xml：

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.apache.derby</groupId>
        <artifactId>derby</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

***************************
APPLICATION FAILED TO START
***************************

Description:
Field topicRepository in com.bloodynacho.rishab.topics.TopicService required a bean of type 'com.bloodynacho.rishab.topics.TopicRepository' 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.bloodynacho.rishab.topics.TopicRepository' in your configuration.
Process finished with exit code 1

编辑：我读了这篇文章，解释了即使没有实际实现@Autowired接口是如何工作的。我明白解决办法，但我不明白如何解决我的问题。显然，Spring数据的设置和配置方式存在一些问题（如答案中所述）

Answer 1

因为如果您的其他包层次结构在您的主应用程序下面，带有@springbootapplication注释，那么您将被隐式组件扫描覆盖。

因此，一个简单的解决方案可以通过以下两个步骤完成：

1. 将main类的包重命名为com.bloodynacho.rishab.
   （这是我建议main app的完整包名应该是其他包的根。）
2. 删除@componentscan和@entityscan注释。
   （尽管@componentscan与@entityscan不同，但根据我的经验，也可以删除。）