无法在 Spring Boot 中拦截和操作 HttpServletResponse

Question

我需要Base64解码 Spring Boot 服务收到的每个 JSON 请求负载。Base64在使用 HTTPPOST方法发布之前，JSON 有效负载将在客户端进行编码。此外，我还需要Base64在呈现给调用客户端应用程序之前对 JSON 响应进行编码。

我需要通过使用处理程序拦截器来减少样板代码。我已经通过使用拦截器实现了操作的请求/传入分支，但尚未为响应分支实现这一点。我已经发布了下面的代码片段。拦截响应和 base64 编码的代码在拦截器类的 postHandle 方法中。

我在这里做错了什么？

拦截器类：

public class Base64ResponseEncodingInterceptor implements HandlerInterceptor {   
    private static final String DECODED_REQUEST_ATTRIB = "decodedRequest";
    private static final String POST = "POST";


    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView arg3) throws Exception {
          try {
              if (POST.equalsIgnoreCase(request.getMethod())) {
                    CharResponseWrapper res = new CharResponseWrapper(response);
                    res.getWriter();
                    byte[] encoded = Base64.encodeBase64(res.toString().getBytes());
                    byte[] encoded = Base64.encodeBase64(response.getHeader(ENCODED_RESPONSE_ATTRIB).getBytes());
                    response.getWriter().write(new String(encoded));
              }
          } catch (Exception e) {
              throw new Exception(e.getMessage());
          }
    }


    // preHandle and afterCompletion methods
    // Omitted 
}

CharResponseWrapper上面使用的类：

public class CharResponseWrapper extends HttpServletResponseWrapper {

    protected CharArrayWriter charWriter;

    protected PrintWriter writer;

    protected boolean getOutputStreamCalled;

    protected boolean getWriterCalled;


    public CharResponseWrapper(HttpServletResponse response) {
        super(response);
        charWriter = new CharArrayWriter();
    }


    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        if (getWriterCalled) {
            throw new IllegalStateException("getWriter already called");
        }
        getOutputStreamCalled = true;
        return super.getOutputStream();
    }


    @Override
    public PrintWriter getWriter() throws IOException {
        if (writer != null) {
            return writer;
        }
        if (getOutputStreamCalled) {
            throw new IllegalStateException("getOutputStream already called");
        }
        getWriterCalled = true;
        writer = new PrintWriter(charWriter);
        return writer;
    }


    @Override
    public String toString() {
        String s = null;
        if (writer != null) {
            s = charWriter.toString();
        }
        return s;
    }
}

注册拦截器的 JavaConfig 类：

@Configuration
@EnableJpaRepositories(repositoryBaseClass = BaseRepositoryBean.class, basePackages = "")
@EntityScan(basePackages = { "com.companyname", "com.companyname.productname"})
public class RestConfig extends WebMvcConfigurerAdapter {


      @Override
      public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new Base64ResponseEncodingInterceptor());
      }

}

使用拦截器的控制器类（此处仅显示了工作请求段）：

@Autowired
HttpServletRequest request;

String decodedRequest = null;

@ModelAttribute("decodedRequest")
public void getDecodedParam(){
    decodedRequest = (String) request.getAttribute("decodedRequest");
} 

postHandle方法中的代码不起作用。它要么HttpServletResponse是null要么我收到一条异常消息：

getOutputStream 已调用

更新：解决直接在 ResponseBodyAdvice 中读取响应的解决方案 在控制器类中，我添加了以下内容：

@RestController
@RequestMapping("/api/ipmanager")
public class IPProfileRestController extends AbstractRestController {

    @Autowired
    HttpServletResponse response;

   String encodedResponse = null;

   @ModelAttribute("encodedResponse")
    public void getEncodedResponse(){
       response.setHeader("encodedResponse", StringUtils.EMPTY);
    } 

    @RequestMapping(value = "/time", method = { RequestMethod.POST }, produces = { MediaType.APPLICATION_JSON_VALUE, MediaType.TEXT_PLAIN_VALUE }, consumes = {
            MediaType.APPLICATION_JSON_VALUE })
    public @ResponseBody String saveAccessClientTime(@RequestBody String ecodedRequest) {

        // Some code here

        String controllerResponse = prettyJson(iPProfileResponse);
        response.setHeader("encodedResponse", controllerResponse);
        return controllerResponse;
    }
}

我在ResponseBodyAdvice 中有以下内容

@ControllerAdvice
public class Base64EncodedResponseBodyAdvice implements ResponseBodyAdvice<Object> {

    @Override
    public boolean supports(MethodParameter returnType, 
                            Class<? extends HttpMessageConverter<?>> converterType) {
        return true;
    }

    @Override
    public Object beforeBodyWrite(Object body,
                                  MethodParameter returnType,
                                  MediaType selectedContentType,
                                  Class<? extends HttpMessageConverter<?>> converterType,
                                  ServerHttpRequest request,
                                  ServerHttpResponse response) {

        String body1 = StringUtils.EMPTY;
        // Encode the response and return

        List<String> listOfHeaderValues = response.getHeaders().get("encodedResponse");

        body1=new String(Base64.encodeBase64(listOfHeaderValues.get(0).getBytes()));

        return body1;
    }

}

Answer 1

正如Spring MVC 文档所述：

的postHandle方法HandlerInterceptor并不总是非常适合@ResponseBody与ResponseEntity方法一起使用。在这种情况下，HttpMessageConverter在postHandle调用之前写入并提交响应，这使得无法更改响应，例如添加标头。相反，应用程序可以实现ResponseBodyAdvice并将其声明为 @ControllerAdvicebean 或直接在 RequestMappingHandlerAdapter.

话虽如此：

我在这里做错了什么？

由于响应已经提交，您无法更改它。为了更改响应，您应该注册一个ResponseBodyAdvice<T>并将您的响应编码逻辑放在那里：

@ControllerAdvice
public class Base64EncodedResponseBodyAdvice implements ResponseBodyAdvice<Object> {
    @Override
    public boolean supports(MethodParameter returnType, 
                            Class<? extends HttpMessageConverter<?>> converterType) {
        return true;
    }

    @Override
    public Object beforeBodyWrite(Object body,
                                  MethodParameter returnType,
                                  MediaType selectedContentType,
                                  Class<? extends HttpMessageConverter<?>> converterType,
                                  ServerHttpRequest request,
                                  ServerHttpResponse response) {

        // Encode the response and return
    }
}