[jira] Commented: (DERBY-3401) Removing a ConnectionEventListener from a PooledConnection during its connectionClosed() callback causes other ConnectionEventListener callbacks to be missed

["Knut Anders Hatlen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DERBY-3401?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12598325#action_12598325 ] 

Knut Anders Hatlen commented on DERBY-3401:
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I think this is also a problem for the statement event listeners (JDBC 4.0 feature).

> Removing a ConnectionEventListener from a PooledConnection during its connectionClosed() callback causes other ConnectionEventListener callbacks to be missed
> -------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-3401
>                 URL: https://issues.apache.org/jira/browse/DERBY-3401
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC
>    Affects Versions: 10.4.1.3
>            Reporter: Daniel John Debrunner
>            Priority: Minor
>
> A ConnectionEventListener should be able to remove itself as a listener during a callback without affecting any other callbacks.
> DataSourceTest.subtestPooledRemoveListenerOnClose() tests the scenario but calls to it will be commented out in the fixture testPooledReuseOnClose() (using this bug number).
> Issue is that such a remove will modify the eventListener Vector in EmbedPooledConnection while it is being enumerated over.
> An idea for a fix would be to first change the Vector over to a new-style collection, such as an implementation of List, then work off a copy of the collection when calling the callbacks. I don't think eventListener needs to be a synchronized collection, its access should be already synchronized on EmbedPooledConnection.
> I imagine that a similar issue exists for adding a new callback during callback processing, fixing this bug would fix that issue as well though no tests have been written for the add case.

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