解决spring cloud gateway 获取body内容并修改的问题

/**
 * @author tengdj
 * @date 2019/8/13 11:08
 * 设备接口验签，解密
 **/
@Slf4j
public class TerminalSignFilter implements GatewayFilter, Ordered {

 private static final String AES_SECURTY = "XXX";
 private static final String MD5_SALT = "XXX";

 @Override
 public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
 exchange.getAttributes().put("startTime", System.currentTimeMillis());
 if (exchange.getRequest().getMethod().equals(HttpMethod.POST)) {
  //重新构造request，参考ModifyRequestBodyGatewayFilterFactory
  ServerRequest serverRequest = ServerRequest.create(exchange, HandlerStrategies.withDefaults().messageReaders());
  MediaType mediaType = exchange.getRequest().getHeaders().getContentType();
  //重点
  Mono<String> modifiedBody = serverRequest.bodyToMono(String.class).flatMap(body -> {
  //因为约定了终端传参的格式，所以只考虑json的情况，如果是表单传参，请自行发挥
  if (MediaType.APPLICATION_JSON.isCompatibleWith(mediaType) || MediaType.APPLICATION_JSON_UTF8.isCompatibleWith(mediaType)) {
   JSONObject jsonObject = JSONUtil.toJO(body);
   String paramStr = jsonObject.getString("param");
   String newBody;
   try{
   newBody = verifySignature(paramStr);
   }catch (Exception e){
   return processError(e.getMessage());
   }
   return Mono.just(newBody);
  }
  return Mono.empty();
  });
  BodyInserter bodyInserter = BodyInserters.fromPublisher(modifiedBody, String.class);
  HttpHeaders headers = new HttpHeaders();
  headers.putAll(exchange.getRequest().getHeaders());
  //猜测这个就是之前报400错误的元凶，之前修改了body但是没有重新写content length
  headers.remove("Content-Length");
  //MyCachedBodyOutputMessage 这个类完全就是CachedBodyOutputMessage，只不过CachedBodyOutputMessage不是公共的
  MyCachedBodyOutputMessage outputMessage = new MyCachedBodyOutputMessage(exchange, headers);
  return bodyInserter.insert(outputMessage, new BodyInserterContext()).then(Mono.defer(() -> {
  ServerHttpRequest decorator = this.decorate(exchange, headers, outputMessage);
  return returnMono(chain, exchange.mutate().request(decorator).build());
  }));
 } else {
  //GET 验签 
  MultiValueMap<String, String> map = exchange.getRequest().getQueryParams();
  if (!CollectionUtils.isEmpty(map)) {
  String paramStr = map.getFirst("param");
  try{
   verifySignature(paramStr);
  }catch (Exception e){
   return processError(e.getMessage());
  }
  }
  return returnMono(chain, exchange);
 }
 }

 @Override
 public int getOrder() {
 return 1;
 }

 private Mono<Void> returnMono(GatewayFilterChain chain,ServerWebExchange exchange){
 return chain.filter(exchange).then(Mono.fromRunnable(()->{
  Long startTime = exchange.getAttribute("startTime");
  if (startTime != null){
  long executeTime = (System.currentTimeMillis() - startTime);
  log.info("耗时：{}ms" , executeTime);
  log.info("状态码：{}" , Objects.requireNonNull(exchange.getResponse().getStatusCode()).value());
  }
 }));
 }

 private String verifySignature(String paramStr) throws Exception{
 log.info("密文{}", paramStr);
 String dParamStr;
 try{
  dParamStr = AESUtil.decrypt(paramStr, AES_SECURTY);
 }catch (Exception e){
  throw new Exception("解密失败！");
 }
 log.info("解密得到字符串{}", dParamStr);
 String signature = SignUtil.sign(dParamStr, MD5_SALT);
 log.info("重新加密得到签名{}", signature);
 JSONObject jsonObject1 = JSONUtil.toJO(dParamStr);
 if (!jsonObject1.getString("signature").equals(signature)) {
  throw new Exception("签名不匹配！");
 }
 return jsonObject1.toJSONString();
 }

 private Mono processError(String message) {
  /*exchange.getResponse().setStatusCode(HttpStatus.UNAUTHORIZED);
  return exchange.getResponse().setComplete();*/
 log.error(message);
 return Mono.error(new Exception(message));
 }

 ServerHttpRequestDecorator decorate(ServerWebExchange exchange, HttpHeaders headers, MyCachedBodyOutputMessage outputMessage) {
 return new ServerHttpRequestDecorator(exchange.getRequest()) {
  public HttpHeaders getHeaders() {
  long contentLength = headers.getContentLength();
  HttpHeaders httpHeaders = new HttpHeaders();
  httpHeaders.putAll(super.getHeaders());
  if (contentLength > 0L) {
   httpHeaders.setContentLength(contentLength);
  } else {
   httpHeaders.set("Transfer-Encoding", "chunked");
  }
  return httpHeaders;
  }
  public Flux<DataBuffer> getBody() {
  return outputMessage.getBody();
  }
 };
 }
}

spring:
 cloud:
  gateway:
   routes:
   - id: header
    uri: http://localhost:8888/header
    filters:
    - AddRequestHeader=NewHeader, Bar
    - AddRequestParameter=NewParam, Param
    predicates:
    - Path=/header