Spring Webflux : Webclient : Get body on error

Question

I am using the webclient from spring webflux, like this :

WebClient.create()
            .post()
            .uri(url)
            .syncBody(body)
            .accept(MediaType.APPLICATION_JSON)
            .headers(headers)
            .exchange()
            .flatMap(clientResponse -> clientResponse.bodyToMono(tClass));

It is working well. I now want to handle the error from the webservice I am calling (Ex 500 internal error). Normally i would add an doOnError on the "stream" and isu the Throwable to test the status code,

But my issue is that I want to get the body provided by the webservice because it is providing me a message that i would like to use.

I am looking to do the flatMap whatever happen and test myself the status code to deserialize or not the body.

Answer 1

I prefer to use the methods provided by the ClientResponse to handle http errors and throw exceptions:

WebClient.create()
         .post()
         .uri( url )
         .body( bodyObject == null ? null : BodyInserters.fromValue( bodyObject ) )
         .accept( MediaType.APPLICATION_JSON )
         .headers( headers )
         .exchange()
         .flatMap( clientResponse -> {
             //Error handling
             if ( clientResponse.statusCode().isError() ) { // or clientResponse.statusCode().value() >= 400
                 return clientResponse.createException().flatMap( Mono::error );
             }
             return clientResponse.bodyToMono( clazz )
         } )
         //You can do your checks: doOnError (..), onErrorReturn (..) ...
         ...

In fact, it's the same logic used in the DefaultResponseSpec of DefaultWebClient to handle errors. The DefaultResponseSpec is an implementation of ResponseSpec that we would have if we made a retrieve() instead of exchange().