使用 spring @RestController 在 null 上返回 HTTP 204

Question

這將返回 200 OK 內容長度：0

@RestController
public class RepoController {
    @RequestMapping(value = "/document/{id}", method = RequestMethod.GET)
    public Object getDocument(@PathVariable long id) {
       return null;
    }

}

簡單地說，我希望它在 null 上返回 204 No Content。

有沒有辦法強制 spring-mvc/rest 在 null 而不是 200 時返回 204？ 我不想改變每個休息方法來返回 ResponseEntity 或類似的東西，只將 null 映射到 204

Answer 1

您可以使用@ResponseStatus注釋。 這樣您就可以擁有一個 void 方法，而不必構建一個 ResponseEntity。

@DeleteMapping(value = HERO_MAPPING)
@ResponseStatus(value = HttpStatus.NO_CONTENT)
public void delete(@PathVariable Long heroId) {
    heroService.delete(heroId);
}

順便說一句，當對象存在時返回 200，否則返回 204，否則對於 API REST 設計來說有點不尋常。 當未找到請求的對象時，返回 404（未找到）是很常見的。 這可以使用 ControllerAdvice 來實現。

在 Spring REST 中，最好使用異常處理程序處理異常，而不是放置邏輯來決定響應狀態等。這是使用 @ControllerAdvice 注釋的示例： http : //www.jcombat.com/spring/exception-handling- in-spring-restful-web-service

Answer 2

當然是的。

選項1 ：

@RestController
public class RepoController {
    @RequestMapping(value = "/document/{id}", method = RequestMethod.GET)
    public Object getDocument(@PathVariable long id, HttpServletResponse response) {
       Object object = getObject();
       if( null == object ){
          response.setStatus( HttpStatus.SC_NO_CONTENT);
       }
       return object ;
    }
}

選項2：

@RestController
public class RepoController {
    @RequestMapping(value = "/document/{id}", method = RequestMethod.GET)
    public Object getDocument(@PathVariable long id) {
       Object object = getObject();
       if ( null == object ){
          return new ResponseEntity<Void>(HttpStatus.NO_CONTENT);
       }

       return object ;
    }
}

可能有錯別字，但你明白了。

Answer 3

我用過濾器解決了這個問題。 它是全球性的，而且很簡單。

package your.package.filter;

import org.springframework.http.HttpStatus;
import org.springframework.web.filter.OncePerRequestFilter;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class NoContentFilter extends OncePerRequestFilter {

    @Override
    protected void doFilterInternal(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, FilterChain filterChain) throws ServletException, IOException {
        filterChain.doFilter(httpServletRequest, httpServletResponse);
        if (httpServletResponse.getContentType() == null ||
                httpServletResponse.getContentType().equals("")) {
            httpServletResponse.setStatus(HttpStatus.NO_CONTENT.value());
        }
    }
}

並在您的 web.xml 中添加以下內容

<filter>
    <filter-name>restNoContentFilter</filter-name>
    <filter-class>your.package.filter.NoContentFilter</filter-class>
</filter>

<filter-mapping>
    <filter-name>restNoContentFilter</filter-name>
    <url-pattern>/rest/*</url-pattern>
</filter-mapping>

Answer 4

你可以試試這個：

@RestController
public class RepoController {

    @RequestMapping(value = "/document/{id}", method = RequestMethod.GET)
    public ResponseEntity<String> getDocument(@PathVariable long id) {

       if(noError) {
           ............
           return new ResponseEntity<String>(HttpStatus.OK); 
       }
       else {
           return new ResponseEntity<String>(HttpStatus.BAD_REQUEST);
       }
   }
}

你需要改變 HttpStatus.BAD_REQUEST 與 204 代碼狀態的等價物

Answer 5

問題很老，但對於那些需要全局答案並擁有 Spring 4+ 的人，您可以創建一個 ResponseBodyAdvice，根據控制器響應更改響應代碼。 以下示例為所有 @RestController 類執行此操作：

@ControllerAdvice(annotations = { RestController.class })
public class NullToNoContentResponseBodyAdvice
    implements ResponseBodyAdvice<Object>
{
    /**
     * {@inheritDoc}
     */
    @Override
    public Object beforeBodyWrite(final Object p_responseBodyObject, final MethodParameter p_methodParameter,
                                  final MediaType p_mediaType, final Class<? extends HttpMessageConverter<?>> p_class,
                                  final ServerHttpRequest p_serverHttpRequest,
                                  final ServerHttpResponse p_serverHttpResponse)
    {
        // ------------------------- DECLARE -------------------------- //

        if (p_responseBodyObject == null)
        {
            p_serverHttpResponse.setStatusCode(HttpStatus.NO_CONTENT);
        }

        // Always return object unchanged or it will break response
        return p_responseBodyObject;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean supports(final MethodParameter p_methodParameter, final Class<? extends HttpMessageConverter<?>> p_class)
    {
        return AbstractGenericHttpMessageConverter.class.isAssignableFrom(p_class);
    }
}

Answer 6

相同的答案，但由 AOP 解決：

@Aspect
public class NoContent204HandlerAspect {

  @Pointcut("execution(public * xx.xxxx.controllers.*.*(..))")
  private void anyControllerMethod() {
  }

  @Around("anyControllerMethod()")
  public Object handleException(ProceedingJoinPoint joinPoint) throws Throwable {

    Object[] args = joinPoint.getArgs();

    Optional<HttpServletResponse> response = Arrays.asList(args).stream().filter(x -> x instanceof HttpServletResponse).map(x -> (HttpServletResponse)x).findFirst();

    if (!response.isPresent())
      return joinPoint.proceed();

    Object retVal = joinPoint.proceed();
    if (retVal == null)
      response.get().setStatus(HttpStatus.NO_CONTENT.value());

    return retVal;
  }
}

Answer 7

您可以自定義HttpMessageConverter來支持這一點，正如我所做的那樣，將spring.http.converters.preferred-json-mapper=gson到application.properties配置文件，結果建議如下：

@ControllerAdvice
public class CommonResultAdvice implements ResponseBodyAdvice<Object> {
@Override
public boolean supports(MethodParameter methodParameter, Class<? extends HttpMessageConverter<?>> aClass) {
    return true;
}

@Override
public Object beforeBodyWrite(Object o, MethodParameter methodParameter, MediaType mediaType, Class<? extends HttpMessageConverter<?>> aClass, ServerHttpRequest serverHttpRequest, ServerHttpResponse serverHttpResponse) {

    if (null == o) {
    //set http code
        serverHttpResponse.setStatusCode(HttpStatus.NO_CONTENT);
        return BaseResult.success();
    }

    if (o instanceof String) {
        ObjectMapper mapper = new ObjectMapper();
        try {
            return mapper.writeValueAsString(BaseResult.success(o));
        } catch (JsonProcessingException ignore) {
        }
    }

    if (o instanceof BaseResult) {
        return o;
    }
    return BaseResult.success(o);
}

}

或者像這樣自定義一個HttpMessageConverter ：

@Configuration
public class BeanConfiguration {
@Bean
public HttpMessageConverter resultToJsonConverter() {
    return new GsonHttpMessageConverter();
}
}

希望能幫到你。 :)