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https://issues.apache.org/jira/browse/OGNL-20?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13108027#comment-13108027
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Adrian Crum commented on OGNL-20:
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Daniel: It appears that you are trying to implement a generic Object cache. If
the cached objects are mutable, then the legacy cache and the read-write-lock
cache will not work - because there is the potential for more than one instance
of the object being created and returned. So, you would have threads using
different "versions" of the object. That potential problem is what the
ConcurrentHashMap.putIfAbsent method solves - it insures that only one copy of
the object is returned.
> Performance - Replace synchronized blocks with ReentrantReadWriteLock
> ---------------------------------------------------------------------
>
> Key: OGNL-20
> URL: https://issues.apache.org/jira/browse/OGNL-20
> Project: OGNL
> Issue Type: Improvement
> Environment: ALL
> Reporter: Greg Lively
> Attachments: Bench Results.txt, Caching_Mechanism_Benchmarks.patch
>
>
> I've noticed a lot of synchronized blocks of code in OGNL. For the most part,
> these synchronized blocks are controlling access to HashMaps, etc. I believe
> this could be done far better using ReentrantReadWriteLocks.
> ReentrantReadWriteLock allows unlimited concurrent access, and single threads
> only for writes. Perfect in an environment where the ratio of reads is far
> higher than writes; which is typically the scenario for caching. Plus the
> access control can be tuned for reads and writes; not just a big
> synchronized{} wrapping a bunch of code.
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