Modify Request Body for a GET request

We currently have custom code for modifying request body which works but I want to move to the standard ModifyRequestBodyGatewayFilterFactory.

We have a scenario where Spring Cloud Gateway received a GET request and we need call an internal GraphQL api with a POST and a request body.

ModifyRequestBodyGatewayFilterFactory works great if there is a body present in the original request but doesn’t apply the rewriteFunction when there is no body on GET requests.

I am using v2.1.2.RELEASE and I have hacked together a change to ModifyRequestBodyGatewayFilterFactory which works for me:

Mono<?> modifiedBody = serverRequest.bodyToMono(inClass)
        .defaultIfEmpty("") //added this line
        .flatMap(o -> config.rewriteFunction.apply(exchange, o));

I appreciate that the ModifyRequestBodyGatewayFilterFactory is beta, but would it be possible to support adding a body for GET requests in the future?

[spencergibb]

I’m not sure I like the edit.

I think I prefer this (closer to what was there prior to the edit).

.switchIfEmpty((Mono) config.rewriteFunction.apply(exchange, null)); //added this line

I don’t like the idea of having a body with an empty string. I also think it might need to be opt-in since it is very unusual.

[gberche-orange]

I’m not sure this exactly covers the use-case of this issue, but I worked around empty body in usage of modifyRequestBody by testing for null the original body and returning Mono.empty() when null body.

.modifyRequestBody(String.class, String.class,
							(webExchange, originalBody) -> {
								if (originalBody != null) {
                                                                       //modify body
                                                                       [...]
									return Mono.just(originalBody);
								} else {
									return Mono.empty();
								}
							})

and submitted https://github.com/spring-cloud/spring-cloud-gateway/pull/2000