How does the close() method work when working with a database connection pool?

When calling close() on a connection obtained from the pool:

1. The connection is not physically closed.
2. It is returned back to the connection pool.
3. The pool may perform a validity check on the connection before reusing it.
4. If the connection is invalid (e.g., timeout on the database side), the pool may close it and, if necessary, create a new one.
5. The connection becomes available for other clients to obtain from the pool.

This helps avoid the overhead of creating and closing a physical connection for each request.