You have to validate the connection.
If you use Oracle it is likely that you use Oracle´s Universal Connection Pool. The following assumes that you do so.
The easiest way to validate the connection is to tell Oracle that the connection must be validated while borrowing it. This can be done with
pool.setValidateConnectionOnBorrow(true);
But it works only if you hold the connection for a short period. If you borrow the connection for a longer time, it is likely that the connection gets broken while you hold it. In that case you have to validate the connection explicitly with
if (connection == null || !((ValidConnection) connection).isValid())
See the Oracle documentation for further details.