java - Spring Boot 使用请求范围的 bean 进行依赖注入(inject)

Question

我正在尝试将一个bean依赖注入(inject)到另一个bean中，但我想通过简单地直接 Autowiring 到类中来实现这一点，而不是通过“@Configuration类”。这是 Controller 类:

@Controller
public class RestfulSourceController {

    @Autowired
    Response response;

    @RequestMapping(value="/rest", method=RequestMethod.GET, produces="application/json")
    @ResponseBody
    public Object greeting() {
        return response.getResponse();
    }

}

这里是“@Configuration”类，每个类中都声明了一个 bean

@Configuration
class RequestConfigurationBeans {

    @Autowired
    private ServicesRepository servicesRepo;

    @Autowired
    private HttpServletRequest request;

    @Bean(name = 'requestServiceConfig')
    @Scope(value=WebApplicationContext.SCOPE_REQUEST, proxyMode=ScopedProxyMode.TARGET_CLASS)
    public ServiceModel requestServiceConfig(){
        String serviceName = RequestUtil.getServiceName(this.request)
        ServiceModel serviceModel = servicesRepo.findByName(serviceName)
        return serviceModel
    }

}

和

@Configuration
public class ServletFilterBeans {

    /* I don't want to autowire here, instead I want to autowire in the Response class directly, instead of passing the bean reference into the constructor
    @Autowired
    ServiceModel requestServiceConfig
    */

    @Bean
    @Scope(value=WebApplicationContext.SCOPE_REQUEST, proxyMode=ScopedProxyMode.TARGET_CLASS)
    public Response response(){
        return new Response(/*requestServiceConfig*/);
    }

}

最后是 Response 类:

class Response {

    //I want to Autowire the bean instead of passing the reference to the constructor
    @Autowired
    ServiceModel requestServiceConfig

    Object response

    public Response(/*ServiceModel requestServiceConfig*/){
        //this.requestServiceConfig = requestServiceConfig

        if (requestServiceConfig.getType() == 'rest'){
            this.response = getRestfulSource()
        }

    }


    private Object getRestfulSource(){
        RestTemplate restTemplate = new RestTemplate()
        String url = requestServiceConfig.sourceInfo.get('url')
        return restTemplate.getForObject(url, Object.class)
    }
}

但是，当我像这样设置依赖注入(inject)时，我收到一个空指针异常，因为 Autowiring 的 bean“requestServiceConfig”未实例化。如何使用 Autowiring 来依赖注入(inject) bean，这样我就不必通过构造函数传递对 bean 的引用？

Answer 1

问题是在 Response 的构造函数中使用了 requestServiceConfig。 Autowiring 只能在对象创建后发生，因此这里的依赖关系只能为空。

要解决问题并能够使用 Autowiring ，您可以将代码从构造函数移动到 @PostConstruct 生命周期方法:

@PostConstruct
private void init() {
    if ("rest".equals(this.requestServiceConfig.getType())) {
        this.response = getRestfulSource();
    }
}