RFR: 8336654: [lworld] Tests depending on sun.awt.AppContext can fail when run with migrated classes [v5]

[Sergey Bylokhov]

On Tue, 6 Jan 2026 18:25:50 GMT, Phil Race <prr at openjdk.org> wrote:

>> The problem is that Boolean will be a value type in the future (Project Valhalla)
>> and so it can't be the referent of a Reference.
>> 
>> In this code, the abstract class that creates the Reference accepts a generic type so isn't in control of what it receives.
>> 
>> The concrete class that extends the generic class has no idea what the super class implementation does,
>> so has no way to know that it might do something that is invalid for  a value type.
>> 
>> That's an interesting observation for Valhalla (that the code that does something inappropriate for a value type
>> isn't the source of the value type) but I don't think we need to be concerned
>> about that here because we can see reasons to do this anyway.
>> 
>> The specific classes exist because a nominal singleton for the VM may need to be private to an AppContext.
>> This is  a concept from applets but also from webstart where we have a single JVM that may be running code
>> from different origins that needs to be partitioned and sand boxed.
>> 
>> This concept is obsolete now as applets and webstart are no longer supported, and the Security Manager
>> is disabled, further undermining any way to support partitioning.
>> 
>> This specific case of a Boolean created from the value of a Java System Property looks like it never needed
>> this partitioning, so the minimal fix is to stop using RecyclableSingleton for it, and just cache the value of that.
>> 
>> The next  level of fix is to note that since AppContext is obsolete, there is no need for RecyclableSingleton
>> to use AppContext specific values, making RecyclableSingleton just a lazy initialization mechanism for the singleton.
>> 
>> Given that removing the obsolete AppContext is on the TBD list - and some JDK components have already
>> removed per-AppContext code - and we'd probably come back to this in JDK 25 anyway it seems best
>> to get it over with.
>> 
>> That does mean that one other place in sun.awt.ImageCache needed to be updated too.
>> 
>> Also one test that explicitly checked that AppContexts were used for UI instances is obsolete and removed.
>> 
>> Note that RecyclableSingleton also offers some lazy initialisation benefit, and is widely used in Aqua,
>> so going further and removing that probably isn't something we want to do at all, and certainly not here.
>
> Phil Race has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8336654

Marked as reviewed by serb (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/22868#pullrequestreview-3637285154