Spring Boot中读取HttpServletRequest请求体后如何转发同请求至另一端点

方法一：自定义HttpServletRequestWrapper缓存请求体（Servlet环境） #

核心思路：通过包装类缓存已读取的请求体，后续调用getInputStream()/getReader()时直接返回缓存内容

• 实现步骤：
  1. 编写自定义请求包装类，继承HttpServletRequestWrapper：

     public class CachedBodyHttpServletRequest extends HttpServletRequestWrapper {
         private byte[] cachedBody;
     
         public CachedBodyHttpServletRequest(HttpServletRequest request) throws IOException {
             super(request);
             // 读取原始请求体并缓存
             this.cachedBody = StreamUtils.copyToByteArray(request.getInputStream());
         }
     
         @Override
         public ServletInputStream getInputStream() throws IOException {
             return new CachedServletInputStream(this.cachedBody);
         }
     
         @Override
         public BufferedReader getReader() throws IOException {
             return new BufferedReader(new InputStreamReader(new ByteArrayInputStream(this.cachedBody)));
         }
     
         // 实现自定义ServletInputStream
         private static class CachedServletInputStream extends ServletInputStream {
             private final ByteArrayInputStream inputStream;
     
             public CachedServletInputStream(byte[] cachedBody) {
                 this.inputStream = new ByteArrayInputStream(cachedBody);
             }
     
             @Override
             public int read() throws IOException {
                 return inputStream.read();
             }
     
             @Override
             public boolean isFinished() {
                 return inputStream.available() == 0;
             }
     
             @Override
             public boolean isReady() {
                 return true;
             }
     
             @Override
             public void setReadListener(ReadListener listener) {
                 throw new UnsupportedOperationException("不支持该操作");
             }
         }
     }
     

  2. 编写Filter替换原始请求：

     @WebFilter(filterName = "CachedBodyFilter", urlPatterns = "/*")
     public class CachedBodyFilter implements Filter {
         @Override
         public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
             HttpServletRequest httpRequest = (HttpServletRequest) request;
             // 用包装类替换原始请求
             CachedBodyHttpServletRequest cachedRequest = new CachedBodyHttpServletRequest(httpRequest);
             chain.doFilter(cachedRequest, response);
         }
     }
     

  3. 启动类添加@ServletComponentScan注解，让Filter生效。

方法二：Spring Cloud Gateway专属方案（响应式环境） #

如果使用Spring Cloud Gateway，不要直接操作原生Servlet API，改用WebFlux提供的响应式API处理

• 编写全局过滤器缓存请求体：

  @Component
  public class RequestBodyCacheFilter implements GlobalFilter, Ordered {
      @Override
      public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
          return exchange.getRequest().getBody()
                  .cache() // 缓存请求体，支持重复订阅
                  .flatMap(dataBuffer -> {
                      // 读取请求体并存入数据库
                      byte[] bodyBytes = new byte[dataBuffer.readableByteCount()];
                      dataBuffer.read(bodyBytes);
                      String requestBody = new String(bodyBytes);
                      // 执行数据库存储逻辑
                      // ...
  
                      // 重新构建请求，将缓存的请求体放回
                      ServerHttpRequest newRequest = exchange.getRequest().mutate()
                              .body(BodyInserters.fromValue(bodyBytes))
                              .build();
                      return chain.filter(exchange.mutate().request(newRequest).build());
                  });
      }
  
      @Override
      public int getOrder() {
          return Ordered.HIGHEST_PRECEDENCE; // 确保过滤器最先执行
      }
  }
  

关键注意事项 #

• Servlet环境下，Filter的执行顺序必须优先于所有需要读取请求体的组件，保证请求被提前包装。
• 处理大请求体时，避免内存溢出，可改用临时文件存储缓存内容。
• Spring Cloud Gateway中禁止混用原生Servlet API，否则会破坏响应式流程，导致后续无法读取请求体。

内容的提问来源于stack exchange，提问作者Ankitha N