Mysql8 didn't detect any abnormality.

[ABin-Huang]

I use mysql8 to test the second connection, and I can get it normally and get the data.
I don't know if it's because of different databases. Can you provide an error message or a screenshot report?

[panchenko]

This is a about a tomcat-jdbc connection pool,
it does not check if returned connection is already closed - https://bz.apache.org/bugzilla/show_bug.cgi?id=64083
I am trying to fix that with apache/tomcat#235

How a database connection could be closed depends on the real setup/database.
In this repo - a real life situation how that can happen with PostgreSQL.