Auto-configure WebClient

[philwebb]

We need a WebClient story to replace RestTemplate in the reactive world.

[snicoll]

I gave some thoughts to that one. If we want to make things consistent, we probably need a WebClientBuilder that takes the converters and other things Spring Boot may auto-configure in the future. It is then a matter of updating @AutoconfigureWebClient.

I don't think we have custom converters support at the moment. When is that scheduled @bclozel ?

[bclozel]

WebClientBuilder is probably the best choice here.
Now about converters, we're in the process or reworking that bit in Framework, since we noticed that sharing an ObjectMapper instance between encoders/decoders can involve a lot of configuration. We should probably wait for SPR-15247 to be fixed before we start writing code in the message encoders/decoders auto-configuration, for both client and server.

[joshiste]

Please also take the WebTestClient into account.

I expected, that the WebTestClient uses the autoconfigured ObjectMapper from the application context, but it doesn't.

Currently adding a new Jackson module to the WebTestClient is a bit tedious and renders the preconfigured WebTestClient useless.

my current solution:

    @Autowired
    private ObjectMapper mapper;

  ...

        webClient = WebTestClient.bindToServer()
                                 .baseUrl("http://localhost:" + port)
                                 .exchangeStrategies(ExchangeStrategies.builder().defaultCodecs((configurer) -> {
                                     configurer.jackson2Decoder(new Jackson2JsonDecoder(mapper));
                                     configurer.jackson2Encoder(new Jackson2JsonEncoder(mapper));
                                 }).build())
                                 .build();

[bclozel]

Oops - I think this one is duplicates by #9577 and #9522 - those are already solved and documented.