Bug #108415 NullPointerException in AbstractQuery::stopQueryTimer

Description:
When the MySQL server dies while queries are being run, the MySQL Connector/J 8.0.30 occasionally fails with a NullPointerException in AbstractQuery::stopQueryTimer, rather than a more useful CommunicationsException.

See https://github.com/mikevink/mysql_connector_j_8_npe/blob/github/readme.md for a more detailed description of the issue.

How to repeat:
See https://github.com/mikevink/mysql_connector_j_8_npe for a sample project that reproduces the issue.

Suggested fix:
The simplest solution would be to add a null-check to AbstractQuery::stopQueryTimer:

if (this.session != null) {
    this.session.getCancelTimer().purge();
}

Hello Markus,

Thank you for the bug report.
Verified as described.

Regards,
Ashwini Patil

I have created a PR to fix this: https://github.com/mysql/mysql-connector-j/pull/92

Contribution submitted via Github - Fix for Bug #108415 - Occasional NPE when server dies 
(*) Contribution by Anthony Milbourne (Github amilbourne, mysql-connector-j/pull/92): This just adds a very simple null-check guard as suggested in the bug report here:
https://bugs.mysql.com/bug.php?id=108415

I have not added a test as this is a very small change and probably not worth the overhead of a test.  Also, this is my first contribution and I have no idea how to test this.

I confirm the code being submitted is offered under the terms of the OCA, and that I am authorized to contribute it.

Contribution: git_patch_1176870298.txt (text/plain), 1.07 KiB.

Duplicated by Bug#112211.

Posted by developer:
 
Added the following entry to the Connector/J 9.1.0 changelog: 

"When a QueryTimer was set, if a session failed, Connector/J returned a NullPointerException. With this fix, a SQL Exception is returned instead. Thanks to Ashwini Patil for contributing to the patch."

Posted by developer:
 
Updated the changelog entry to the following: 

"When a QueryTimer was set, if a session failed, Connector/J returned a NullPointerException. With this fix, a SQL Exception is returned instead. Thanks to Ashwini Patil for contributing to the patch. Thanks to Anthony Milbourne for contributing to the patch."

Posted by developer:
 
Updated the changelog entry to the following: 

"When a QueryTimer was set, if a session failed, Connector/J returned a NullPointerException. With this fix, a SQL Exception is returned instead. Thanks to Anthony Milbourne for contributing to this patch."