How to resoleve memory leak when using Tomcat and Oracle database

There are Servlet applications on tomcat, but when tomcat is stopped

The following memory leak warning is output.

A memory leak actually runs out of DB server resources and goes down A phenomenon has occurred.

Could you tell me about the countermeasures?

Thank you.

【Tomcat logs】

19-Jan-2021 17:03:26.920 alert [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads Web application [ap1] start a named [xxxxx] thread, but it failed to stop.This is very likely to cause a memory leak. Thread stack trace:

 java.lang.Object.wait(Native Method)

 java.lang.Object.wait(Object.java:502)

 java.util.TimerThread.mainLoop(Timer.java:526)

 java.util.TimerThread.run(Timer.java:505)