Helidon Webclient does not seem to work with a proxy

Question

I am facing some trouble with the WebClient when using proxy, i.e. the code below does not work

WebClient webClient = WebClient.builder().baseUri("BASEURL").proxy(getProxy()).build();
Single<WebClientResponse> res = webClient.get().path("/MY/SUB/PATH").addHeader("Authorization", "Bearer " + MY_TOKEN).request();
WebClientResponse webClientRes = res.get();
String resContent = webClientRes.content().as(String.class).get();


public Proxy getProxy(){
    return Proxy.builder().type(Proxy.ProxyType.HTTP).host(host).port(port).password("SECRET_PASSWORD".toCharArray()).username(username).build();
}

However the if we use Apache HttpClient the code works (working code below)

HttpHost proxy = new HttpHost(host, port);
CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
credentialsProvider.setCredentials(new AuthScope(proxy), new UsernamePasswordCredentials(username, "SECRET_PASSWORD"));
HttpGet request = new HttpGet("BASEURL" + "/MY/SUB/PATH");
request.setHeader(HttpHeaders.AUTHORIZATION, "Bearer " + MY_TOKEN);
CloseableHttpClient httpClient = HttpClients.custom().setProxy(proxy).setDefaultCredentialsProvider(credentialsProvider).build();
String resContent = EntityUtils.toString(httpClient.execute(request).getEntity());

could anyone let us know if we are overlooking something basic? We are using helidon MP 2.5.2

Answer 1

When you set a proxy in WebClient, it will use absolute URI in the request because of changes made in https://github.com/helidon-io/helidon/issues/2302 and https://github.com/helidon-io/helidon/issues/3438. The use of absolute URI was implemented because of section 5.1.2 Request-URI in https://www.w3.org/Protocols/rfc2616/rfc2616-sec5.html which states:

The absoluteURI form is REQUIRED when the request is being made to a proxy.

The problem is that some hosts have issue processing a request with absolute URI as they expect relative URI instead. I have encountered while working on issue https://github.com/helidon-io/helidon/issues/4644 where my testcase has a client that is connecting to KeyCloak as an OIDC server, and KeyCloak will return a 404 because it cannot handle the absoluteURI.

There is a special Webclient config property called relative-uris that you can use to force the request URI to use the relative form rather than absolute. So you can try adding config() in your WebClient.builder() and set that property like this:

.config(Config.create(ConfigSources.create(Map.of("relative-uris", "true")))

where Config needs to be imported as io.helidon.config.Config and ConfigSources as io.helidon.config.ConfigSources. As an alternative, you can also add something like this in your application.yaml:

force-relative-uris:
   relative-uris: true

and add config() in the WebClient.builder() like this:

.config(config.get("force-relative-uris"))

where config is instantiated prior to WebClient.builder() like this:

Config config = Config.create();

In the upcoming Helidon v2.5.5 (and v3.0.3), there will be a new relativeUris(boolean relativeUris) in WebClient.builder() so that you don’t have to use config() as in my examples above, which is slightly cumbersome.