JDBC Datasource Memory Leak in Tomcat 7

When shutting down Tomcat 7 using the JDBC datasource, users may encounter a warning message similar to the below:

SEVERE: The web application [/my_webapp] appears to have started a thread named [MySQL Statement Cancellation Timer] but has failed to stop it. This is very likely to create a memory leak.

Addressing the JDBC Driver Registration Issue

To resolve the issue related to unregistering the JDBC driver, ensure that the destroy-method is properly configured within the element in context.xml. The correct configuration should be:

Resolving the MySQL Statement Cancellation Timer Error

To address the error related to the MySQL Statement Cancellation Timer thread, follow these steps:

1. Move the MySQL Connector/Driver to tomcat/lib: Place the MySQL Connector/Driver JAR file in the tomcat/lib directory instead of deploying it within the WAR file. This prevents the creation of multiple instances of the driver upon each WAR deployment.
2. Add a Shutdown Hook to Tomcate: Introduce a shutdown hook to gracefully close the thread. Edit the web.xml file and add the following initialization parameter:

shutdownHookcom.example.MyShutdownHook

Create the MyShutdownHook class to execute upon Tomcat shutdown:

public class MyShutdownHook implements Shutdownable {
    @Override
    public void shutdown() {
        // Logic to properly close the MySQL Statement Cancellation Timer thread
    }
}

By implementing the above solutions, memory leaks related to JDBC datasource usage and the MySQL Statement Cancellation Timer issue can be effectively mitigated in Tomcat 7.