In our test environment, it was observed that there are too many queries were getting fired to the database server,
What does "too many" mean here? Is it just more than you like to see in your log file, or is there some objective problem?
These look like housekeeping queries which are executed by a connection pooler each time a connection is checked out of the pool (or perhaps checked back in). However, they don't seem to be the housekeeping queries which pgbouncer itself uses. I don't think that JDBC automatically issues them either, although that might depend on your configuration. So I think that leaves Tomcat as the most likely culprit. Tomcat does offer a connection pool. Are you using it?