java - Spring : how this field in controller is injected?

Question

我有一个像这样的休息 Controller :

@Slf4j
@RestController
@RequestMapping(...)
public class MyController {

private MyService service;

public MyController(MyService service){
   this.service = service;
}

服务类是一个组件:

@Component
public class MyService{
  ...
}

当我运行程序时，service 字段被正确注入(inject)。但它是如何注入(inject)的(构造函数中的归档ni上都没有 Autowiring 注释)？

我使用的是SpringBoot 2.0。

Answer 1

从 Spring 4.3 版本开始。根据文档( https://docs.spring.io/spring-boot/docs/current/reference/html/using-spring-boot.html#using-boot-spring-beans-and-dependency-injection )，如果 bean 有单个构造函数，则可以省略 @Autowired 注解。

If a bean has one constructor, you can omit the @Autowired, as shown in the following example:

@Service
public class DatabaseAccountService implements AccountService {

    private final RiskAssessor riskAssessor;

    public DatabaseAccountService(RiskAssessor riskAssessor) {
        this.riskAssessor = riskAssessor;
    }

    // ...

}