[
https://issues.apache.org/jira/browse/OGNL-20?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13108134#comment-13108134
]
Adrian Crum commented on OGNL-20:
---------------------------------
Daniel: The DCL design pattern does not enforce a singleton pattern, and it has
concurrency issues also. Again, please read the books I recommended.
Also, the concurrency issue I described has nothing to do with the thread
safety of the cached object. Let's use this class as an example:
{code}
public class Counter {
private int count = 0;
public synchronized void increment() {
this.count++;
}
public synchronized int getCount() {
return this.count;
}
}
{code}
An application starts two threads and each one runs the same process that gets
a Count instance from the cache and then calls increment() four times. After
the two threads terminate, the application gets a Count instance from the cache
and calls getCount(). The value returned is 4. Not what a developer would
expect (8). Yet the Count class is thread-safe.
> 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.
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira
