Add automatic support in WebClient for JVM http.proxyHost and related properties

[tjquinno]

Environment Details

• Helidon Version: 3.x
• Helidon SE or Helidon MP
• JDK version:
• OS:
• Docker version (if applicable):

---

Problem Description

The standard Java system properties http.proxyHost, http.proxyPort, and http.nonProxyHosts (and the https counterparts) govern proxy behavior generally, but not in Helidon's web client.

The request is for Helidon to "intelligently" use those settings automatically, if they exist, in preparing web clients. Presumably, if the developer explicitly sets proxy behavior (via code or configuration) for a web client then, for that client, Helidon would ignore the JVM system property settings.

[AshwinPrabhuB]

"Java Networking and Proxies" has some general conventions described, which most Java developers be habituated to expect OOTB.

Currently, devs have to fall in line by wiring these standard variables into WebClient configuration via ${http.proxyHost} tokens. So why not make this behavior default, and let devs customize/override it via configuration source precedence patterns?

[romain-grecourt]

We should support environment variables too (E.g. http[s]_proxy, no_proxy).
The Proxy configuration class should also have a way to turn off the detection from system properties and environement variables. See this file for inspiration: https://github.com/helidon-io/helidon-build-tools/blob/8cd09fb8e285afc438597ad4b347a5f75add434c/common/common/src/main/java/io/helidon/build/common/Proxies.java#L32

[tomas-langer]

We should already be supporting this through Proxy.ProxyType.SYSTEM - this uses the Java proxy setup and is already in 3.x

[tjquinno]

Tomas, I think the request is that the Proxy.ProxyType.SYSTEM behavior should be the default (unless the developer specifics otherwise, of course) and not require the developer to explicitly choose it, the thought being that Java developers will expect the standard Java system properties to work without taking any further steps.

[tomas-langer]

Created #7274 for Helidon 4.x

[jbescos]

It was merged already