[WARNING] [] [javax.enterprise.web.util] [tid: _ThreadID=18 _ThreadName=RunLevelControllerThread-1473348595597] [timeMillis: 1473348603791] [levelValue: 900] [[ The web application [unknown] registered the JDBC driver [com.mysql.cj.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.]] [/pre]
The GlassFish warning means that your application registered the JDBC driver, but did not unregister it during undeployment. When the application is redeployed, the old version is undeployed and the above warning is thrown. It should not affect newly deployed applications.
It you undeploy all applications, restart the server and deploy your application, you should not see the warning.
1. First undeploy all applications
2. Restart the server
3. deploy application