Document non trivial WebClient configurations [SPR-15778]

[spring-projects-issues]

Abhijit Sarkar opened SPR-15778 and commented

I'm looking to migrate to WebClient from Apache HttpClient that currently has the following configurations. I could not find any of these using the WebClient.

1. Custom javax.net.ssl.SSLContext: I'm accepting all certificates but logging when a certificate fails validation; details in this SO thread.
2. Socket and connection timeouts
3. Retrieving the redirect URLs, if any: HttpClient remembers all the redirect URLs.
4. Caching (Apache has a CachingHttpClients): I'm not very concerned if this feature is not built in the WebClient because I can use Spring cache abstraction. I'd just like to know whether the client has first-class support for caching or not.

In general, when using RestTemplate, there's a whole bunch of ClientHttpRequestFactory implementations to choose from, or customize upon. How do I achieve such flexibility with WebClient so that if I want to switch out the underlying HTTP client, I can?

---

Affects: 5.0 RC2

Referenced from: commits f9e1913

[spring-projects-issues]

Arjen Poutsma commented

Most of these questions are related to Reactor Netty, currently being the only WebClient backend we provide, and as such are best answered there. But I will attempt to answer regardless, and make sure these answers end up in the reference documentation.

1. Custom javax.net.ssl.SSLContext: I'm accepting all certificates but logging when a certificate fails validation; details in this SO thread.

When constructing a ReactorClientHttpConnector, you can use the HttpClientOptions.Builder to further customize it.
For instance, to customize the Netty SslContext:

SslContext sslContext = ...
ReactorClientHttpConnector connector = new ReactorClientHttpConnector(builder -> {
	builder.sslContext(sslContext);
});
WebClient webClient = WebClient.builder()
		.clientConnector(connector)
		.build();

2. Socket and connection timeouts

These are also configured at the Reactor Netty level.

3. Retrieving the redirect URLs, if any: HttpClient remembers all the redirect URLs.

I am not sure what you mean by "remembers all the redirect URLs", but WebClient does not follow Location headers (yet). This might be a customisable feature we add it the future.

4. Caching (Apache has a CachingHttpClients): I'm not very concerned if this feature is not built in the WebClient because I can use Spring cache abstraction. I'd just like to know whether the client has first-class support for caching or not.

It does not.

In general, when using RestTemplate, there's a whole bunch of ClientHttpRequestFactory implementations to choose from, or customize upon. How do I achieve such flexibility with WebClient so that if I want to switch out the underlying HTTP client, I can?

As stated above, we currently only provide a Reactor Netty-based ClientHttpConnector, but there are plans to add a Jetty-based one as well, see #19658.

[spring-projects-issues]

Abhijit Sarkar commented

Thanks for your response. Unfortunately, I don't have the bandwidth to test these out immediately (the devil is always in the details), so I'll take the instructions on face value.