RFR: 7903373: Add ability to customize test execution using main wrapper plugin [v17]

[Jonathan Gibbons]

On Thu, 16 Feb 2023 21:51:00 GMT, Leonid Mesnik <lmesnik at openjdk.org> wrote:

>> The fix adds support of a plugin that customizes test execution.
>
> Leonid Mesnik has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 59 commits:
> 
>  - merge
>  - CHANGELOG.md updated
>  - Renamed TestThreadFactoryProvider.java
>  - fixed i28n
>  - Updated plugin to implement standard ThreadFactory.
>  - removed spaces
>  - updated docs and copyrights
>  - Added new file.
>  - Renamed MainWrapper to TestThreadFactory.
>  - removed DriverTest.java
>  - ... and 49 more: https://git.openjdk.org/jtreg/compare/2f5f2693...f4e9cc63

src/share/classes/com/sun/javatest/regtest/agent/TestThreadFactoryHelper.java line 68:

> 66:             }
> 67:             loader = new URLClassLoader(urls.toArray(new URL[urls.size()]), loader);
> 68:         }

In the `othervm` case, this code will presumably just be called once, but in the `agentvm` case, won't it be called once per test, and since the class loader is never closed, (see [URLCLassLoader.close](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/net/URLClassLoader.html#close())) won't that lead to a leak of any resources that might be involved ... especially any zip/jar files that might be opened?

Is it not worth trying to cache and reuse the loader?

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PR: https://git.openjdk.org/jtreg/pull/136