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From "Grzegorz Borkowski (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DBCP-332) Closing BasicDataSource doesn't deregister JDBC driver, causing memory leak
Date Mon, 24 May 2010 10:56:25 GMT

    [ https://issues.apache.org/jira/browse/DBCP-332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12870567#action_12870567
] 

Grzegorz Borkowski commented on DBCP-332:
-----------------------------------------

I've discovered one problem with unregistering SQL driver in BasicDataSource.close() method:
if you create the BasicDataSource, retrieve connection, close connection, than close BDS,
and than create new instance of BDS, and try to obtain connection, it will not work: it will
complain that it can't find proper driver for given URL. I haven't had time to investigate
it, but I guess that driver registration is done somehow statically, at class loading. So
after you deregister driver and create new instance of BDS, driver is not registered again,
because no classlodin is done at that moment. That's my guess at least. As a solution, the
BDS could try to register manually the driver (using java.sql.DriverManager.registerDriver)
whenever first attempt to obtain driver fails.

> Closing BasicDataSource doesn't deregister JDBC driver, causing memory leak
> ---------------------------------------------------------------------------
>
>                 Key: DBCP-332
>                 URL: https://issues.apache.org/jira/browse/DBCP-332
>             Project: Commons Dbcp
>          Issue Type: Bug
>    Affects Versions: 1.3, 1.4
>            Reporter: Grzegorz Borkowski
>             Fix For: 1.3.1, 1.4.1
>
>
> BasicDataSource's method close() doesn't deregister JDBC driver. This causes permgen
memory leaks in web server environments, during context reloads. For example, using Tomcat
6.0.26 with Spring, and BasicDataSource declared in Spring context, there is a message printed
at web application reload:
> SEVERE: A web application registered the JBDC driver [com.mysql.jdbc.Driver] but failed
to unregister it when the web application was stopped. To prevent a memory leak, the JDBC
Driver has been forcibly unregistered.
> I was able to fix it by overriding close method this way:
> {code}
> public class XBasicDataSource extends BasicDataSource {
>     @Override
>     public synchronized void close() throws SQLException {
>         DriverManager.deregisterDriver(DriverManager.getDriver(url));
>         super.close();
>     }
> }
> {code}
> but I think it should be probably the default behavior of BasicDataSource. Or perhaps
there should be some flag/setting on BasicDataSource, named "deregisterDriverAtClose" or so.

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