RFR: 8359709: java.net.HttpURLConnection sends unexpected "Host" request header in some cases after JDK-8344190

[Daniel Fuchs]

On Tue, 17 Jun 2025 06:55:38 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

> Can I please get a review for this change which addresses a regression that was introduced in `HttpURLConnection` in Java 24 when we cleaned up the code by removing the references to SecurityManager APIs.
> 
> When a HTTP request is issued through `java.net.HttpURLConnection`, then the request URL is used to determine the `Host` header to set in the request. By default, the application cannot set a `Host` header to a different value. However the JDK allows a system property to be enabled to allow applications to explicitly set a `Host` request header when issuing the request.
> 
> Due to an oversight in the change that was done in https://bugs.openjdk.org/browse/JDK-8344190, the `Host` header that is set by the application, may not get used for that request causing this regression. Turns out we don't have tests in this area to catch this issue.
> 
> The commit in this PR fixes the regression and also introduces a new jtreg test which reproduces the issue and verifies the fix.
> 
> I've also checked the original change which introduced this regression https://github.com/openjdk/jdk/pull/22232 to see if there's anything else that needs attention. I haven't stopped anything else.

src/java.base/share/classes/sun/net/www/protocol/http/HttpURLConnection.java line 624:

> 622:                 host += ":" + String.valueOf(port);
> 623:             }
> 624:             if (requests.findValue("Host") == null) {

Should we use `setIfNotSet` here like for "Accept" below?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25844#discussion_r2152281066