How do I get the request body in the global filter method?

[venkatnpedada]

How do I get the request body in the global filter method?

Spring boot 2.1.6
Spring Cloud 2.1.2

Based on this comment (#747 (comment)), I tried to replicate the code, but with spring cloud 2.1.2 some of the classes are removed (CachedBodyOutputMessage)

[ryanjbaxter]

See https://github.com/spring-cloud/spring-cloud-gateway/blob/master/spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/factory/rewrite/ModifyRequestBodyGatewayFilterFactory.java

[venkatnpedada]

Thanks @ryanjbaxter, but with Spring Cloud 2.1.2, CachedBodyOutputMessage class is private, so I can not use the code as it is - https://github.com/spring-cloud/spring-cloud-gateway/blob/master/spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/factory/rewrite/ModifyRequestBodyGatewayFilterFactory.java#L91

[ryanjbaxter]

Fair point, but it doesnt mean you can't copy that class if you need it (I realize that is not ideal).

@spencergibb maybe we should make that class public?

[spencergibb]

we could I guess.

[voidbean]

I used the old version of ReadBodyPredicateFactory to implement this function.
https://github.com/spring-cloud/spring-cloud-gateway/blob/dc4181bbb0/spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/handler/predicate/ReadBodyPredicateFactory.java
And it like this in my global filter:

        return DataBufferUtils.join(exchange.getRequest().getBody())
                .flatMap(dataBuffer -> {
                    DataBufferUtils.retain(dataBuffer);
                    Flux<DataBuffer> cachedFlux = Flux.defer(() -> Flux.just(dataBuffer.slice(0, dataBuffer.readableByteCount())));
                    ServerHttpRequest mutatedRequest = new ServerHttpRequestDecorator(exchange.getRequest()) {
                        @Override
                        public Flux<DataBuffer> getBody() {
                            return cachedFlux;
                        }
                    };
                    ServerWebExchange build = exchange.mutate().request(mutatedRequest).build();
                    return Mono.just(build)
                            .map(ex -> {
                                ServerRequest.create(ex, MESSAGE_READERS)
                                        .bodyToMono(String.class)
                                        .subscribe(
                                                bodyString -> {
                                                    ex.getAttributes().put("requestBody",bodyString);
                                                }
                                        );
                                return ex;
                            })
                            .doOnNext(objectValue -> {
                                exchange.getAttributes().put(CACHE_REQUEST_BODY_OBJECT_KEY, objectValue);
                                exchange.getAttributes().put(CACHED_REQUEST_BODY_KEY, cachedFlux);
                            });
                }).defaultIfEmpty(exchange).flatMap(webExchange -> Mono.just(exchange));

But if you post a request withi empty body,it will cause "Only one connection receive subscriber allowed".So I copied the DataBufferUtils#join and rewrite it to avoid the empty body.

        Mono<DataBuffer> dataBufferMono = Flux.from(exchange.getRequest().getBody()).collectList().filter((list) -> {
            if(list.isEmpty()){
                list.add(new NettyDataBufferFactory(ByteBufAllocator.DEFAULT).allocateBuffer(0));
            }
            return true;
        }).map((list) -> {
            return ((DataBuffer)list.get(0)).factory().join(list);
        }).doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release);
dataBufferMono.flatMap(dataBuffer->(...))

[endypark]

Did not find any good method so far.
You could read the body in customed GlobalFilter，but could not modify the body.
you could @bean r.readBody( sssss ) with DSL , then you could read the body by exchange.getAttribute("cachedRequestBodyObject");

(remember, you could not modify and reset the body. Or I am fool, so did not find the way)

the only method to modify the body content is use Java DSL r.path("/aaa").filters( f -> f.modifyRequestBody( xxxxxx )).uri("lb://aaa") for each route, I did not find any method for all routes ( or default-filters) so far.

[ScarWar]

I use this code to parse the body

private static final String CACHED_REQUEST_BODY_OBJ = "cached_request_body_obj";

private static List<HttpMessageReader<?>> messageReaders =
        HandlerStrategies.withDefaults().messageReaders();

/**
 * This method is inspired by {@link ReadBodyPredicateFactory}
 *
 * @param exchange the current exchange
 * @param inClass  the class to parse the body to
 * @param <T>      the type the body is parsed to
 * @return Mono of type T of the parsed body
 */
static public <T> Mono<T> readBody(ServerWebExchange exchange, Class<T> inClass) {
  T bodyObject = exchange.getAttribute(CACHED_REQUEST_BODY_OBJ);

  return bodyObject != null
          ? Mono.just(bodyObject)
          : getBody(exchange, inClass);
}

private static <T> Mono<T> getBody(ServerWebExchange exchange, Class<T> inClass) {
  return ServerWebExchangeUtils.cacheRequestBodyAndRequest(
          exchange,
          request -> ServerRequest.create(exchange.mutate()
                  .request(request)
                  .build(), messageReaders)
                  .bodyToMono(inClass)
  ).doOnNext(bodyObject -> exchange.getAttributes()
          .put(CACHED_REQUEST_BODY_OBJ, bodyObject)
  );

Sadly it does not work as a standalone. It only works when I use the readBody predicate before as a dummy.

.readBody(inClass, o -> true)
.filters(f -> f
        .filter((exchange, chain) -> {
          return readBody(exchange, inClass)
                  // Do logic with body
                  .then(chain.filter(exchange));
        }))
.uri("http://exmaple.com"))

without it I get

java.lang.IllegalStateException: Only one connection receive subscriber allowed.

The ability to use the request body for custom logic in not a nice-to-have feature but rather a necessity.

[spring-projects-issues]

Closing due to age of the question. If you would like us to look at this issue, please comment and we will look at re-opening the issue.