Document auto-configuration of underlying HTTP client when using WebClient or RestTemplate

[martin-mfg]

Hello,

I am using Spring Boot 2.7. If org.apache.httpcomponents:httpclient is on the class path, Spring Boot uses it automatically inside RestTemplate, as expected. This behaviour is decribed in #16706, but I didn't find documentation about this in any "official" place.
I suggest documenting this somewhere.

Thanks!

[wilkinsona]

Thanks for the suggestion. We briefly document the underlying client that we'll use with WebClient but we don't do the same for RestTemplate. In both cases, I think it would be better if we documented things more clearly as we do for JDBC connection pools.

[julaij]

@wilkinsona I want to work on it and do the documentation, in what page should the documentation go? Please let me know.

[wilkinsona]

Thanks for the offer, @julaij. The source for the existing documentation is https://github.com/spring-projects/spring-boot/blob/2.7.x/spring-boot-project/spring-boot-docs/src/docs/asciidoc/io/rest-client.adoc. Please let us know if you have any questions.

[wilkinsona]

It has been almost two months now so I'm going to take care of this one. It will be good to have this documented, particularly as we're about to add RestTemplate-support for Jetty's client and the JDK's HTTP client.