RFR 8174151: URLClassLoader no longer uses custom URLStreamHandler for jar URLs

[Alan Bateman]

On 13/02/2017 22:52, Paul Sandoz wrote:

> Hi,
>
> Please review.
>
>    http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8174151-url-class-path-loader/webrev/index.html
>
> This is a nasty edge case when a URLStreamHandler is registered (via the system property) to process jar: URLs.
>
> The support for multi-release JAR files changed the implementation of ClassLoader.findResource such that the to be returned jar: URLs would not be operated on, and therefore the jar: URLStreamHandler would not be queried [*]. If the returned jar: URL is operated on by the caller then the jar: URLStreamHandler would (of course) be queried.
>
> This is arguably an implementation detail but it does change long term established behaviour in a very delicate area.
>
> While i find it unpalatable to do so this patch restores the previous behaviour, if a custom jar: URLStreamHandler is registered. The compromise is such a custom jar: URLStreamHandler needs to explicitly support multi-release JAR files.
>
This is really ugly but I think the changes are okay/safe. Initially I 
thought it might be simpler to just use URL.handlers but the API allows 
someone to create a URL with a different URLStreamHandler.

-Alan