Why is Tomcat Forcibly Unregistering My JDBC Driver, and How Can I Prevent It?

JDBC Driver Auto-Registration and De-Registration in Tomcat

When deploying a web application, users may encounter the following error message during shutdown:

SEVERE: A web application registered the JBDC driver [oracle.jdbc.driver.OracleDriver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.

Understanding the Issue

Since Tomcat version 6.0.24, a memory leak detection feature has been implemented. This feature detects JDBC 4.0 compatible drivers that auto-register themselves during web application startup using the ServiceLoader API but fail to auto-deregister during shutdown. To prevent memory leaks, Tomcat forcibly unregisters these drivers.

Possible Solutions

• Ignore the Warning: Tomcat has already taken appropriate action to prevent memory leaks. You can ignore the message as it is an informational warning.
• Move JDBC Driver to Tomcat's /lib Folder: Place the JDBC driver in Tomcat's /lib folder and use a connection pooled datasource to manage the driver. This ensures proper registration and de-registration of the driver.
• Use a Different Connection Pool: If using DBCP for connection pooling, consider switching to a different connection pool such as HikariCP or Tomcat JDBC Pool, which handle driver de-registration more effectively.
• Downgrade to Tomcat 6.0.23 or Older: Downgrading to an older version of Tomcat would suppress the warning, but it would also prevent Tomcat from performing memory leak detection.

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