As described in the JDBC 4 spec, sections 11.2, 11.7, and 3.1.
These are the methods which let app servers listen for connection and statement closure and invalidation events.
Section 11.2 of the JDBC 4 spec explains connection events: Connection pool managers which implement the ConnectionEventListener interface can register themselves to listen for "connectionClosed" and fatal "connectionErrorOccurred" events. App servers can use these events to help them manage the recycling of connections back to the connection pool.
Section 11.7 of the JDBC 4 spec explains statement events: Statement pools which implement StatementEventListener can register themselves to listen for "statementClosed" and "statementErrorOccurred" events. Again, this helps statement pools manage the recycling of statements back to the pool.