Race condition & memory leak in TypedFilter

[jglick]

After starting a controller I got an “angry Jenkins” and in the log I saw

java.lang.NullPointerException: Cannot invoke "java.lang.Boolean.booleanValue()" because the return value of "java.util.Map.get(Object)" is null

coming from the line for staplerCache.get(clazz). This is not all that surprising, since it was a (non-Concurrent) HashMap, and I suppose this cache could be used from multiple page loading threads, so it would be expected to happen occasionally.

Also HashMap rather than WeakHashMap meant that the keys were held strongly. Probably not an issue for Jenkins, assuming this refers only to plugin classes, since plugins cannot be unloaded, but still a bad practice.

CacheValue handles both issues and is simpler to boot.

Testing done

Existing test passes.

Proposed changelog entries

• Fix a rare race condition rendering pages soon after startup.

Proposed upgrade guidelines

N/A

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[jglick]

(hide WS)

[MarkEWaite]

This PR is now ready for merge. We will merge it after approximately 24 hours if there is no negative feedback.

/label ready-for-merge