Spring HTTP Interface Clients should return ResponseEntity even if a 40X or 50X error occurs

Affects: Spring Web 6.1.X

Given a simple method in FooInterface such as

  @GetExchange("/foo")
  Mono<ResponseEntity<Foo>> getFoo();

with a 'standard' WebClient backing it.

The factory is also 'generic':

    HttpServiceProxyFactory factory = HttpServiceProxyFactory
      .builderFor(WebClientAdapter.create(webClient))
      .build();

    return factory.createClient(FooInterface.class);

When the client is used and a 40X or 50X response occurs, then the WebClient throws a WebClientResponseException - which is unexpected - as I would think that having specified Mono<ResponseEntity<Foo>> as the return type would have returned a ResponseEntity with status 40X or 50X (acknowledging the reactive component of this).

Looking at the factory code, it is aware of the return type, and therefore I would expect a response that is consistent with the declared return type - in other words, a Mono<ResponseEntity<Foo>>.

I have not found a way to work around this - meaning obtaining a behavior consistent with the return type - in the same manner that exchange() would work. This is another odd part of this, as exchange() is deprecated and we now work with exchangeToMono() - which is distinctly a client feature that seems too low level to be a part of HTTP interface clients. So maybe - works as designed?

Instead, I've had to use the normal handling of errors to 'coerce' the behavior I want for a given method. With this, I can do what I want, but it seems this may be a bug - or something that can be clarified in the documentation.

Comment From: simonbasle

@amoffet the official way around this is to customize the underlying WebClient, as described in the HTTP interface client documentation's error handling section