Sebb created JCS-115:
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             Summary: JDBCDiskCachePoolAccessManager is thread hostile
                 Key: JCS-115
                 URL: https://issues.apache.org/jira/browse/JCS-115
             Project: Commons JCS
          Issue Type: Bug
            Reporter: Sebb
            Priority: Critical


JDBCDiskCachePoolAccessManager is currently designed as a singleton.

However, it contains a mutable field, props, with a protected setter.

This just does not work in a multi-threaded environment.

It looks like the reason for the singleton is to share a the HashMap of 
JDBCDiskCachePoolAccess instances.

So one possible fix would be to make the HashMap static instead of using a 
singleton, replace getInstance with a public constructor.
AFAICT this won't affect garbage collection of the pool as there is no way to 
clear the singleton reference. 

Another would be to eliminate the props field, adding it as a parameter to 
methods that need it.

It looks as though the props field is only used when creating the entry for the 
map, so it should be supplied at the same time as the pool name. It does not 
appear to be possible to delete a pool entry once created, so a given set of 
props can only be used once to create a pool of a given name.

In any case, the setter for props should be removed and the field should be 
made final (if it is kept).

Note: this was found when investigating JCS-114 - one of the tests fails to 
invoke JDBCDiskCachePoolAccessManager.setProps



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