Why Does Tomcat Forcibly Unregister My JDBC Driver, and How Can I Prevent It?

JDBC Driver Forcibly Unregistered: Memory Leak Prevention

When encountering the error "To prevent a memory leak, the JDBC Driver has been forcibly unregistered," it indicates that a JDBC driver was improperly handled upon web application shutdown. This issue arose with Tomcat versions 6.0.24 and later due to a memory leak detection feature.

Cause of the Error

Service-level JDBC drivers loaded via the class path auto-register during web application startup. However, if the driver fails to deregister itself properly during shutdown, it can lead to memory leaks. Tomcat automatically unregisters these drivers to prevent this issue.

Resolution

• Ignore the Warning: Tomcat has already taken the necessary corrective action, mitigating any potential memory leaks.
• Downgrade Tomcat (Not Recommended): Versions 6.0.23 and earlier will not display this warning, but they may still be susceptible to memory leaks.
• Move the JDBC Driver to Tomcat's Lib Folder: Place the driver in Tomcat's shared "/lib" folder and configure a connection pooled datasource to manage the driver. Avoid using Tomcat's DBCP as it does not properly deregister drivers on close. Consider using alternative connection pools such as HikariCP or Tomcat JDBC Pool.
• Manually Register and Deregister the Driver: If you cannot move the driver to Tomcat's "/lib" folder, you can manually register and deregister the driver using a ServletContextListener.

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