Toplink JPA: jdbc connection access required

Question

I have a strong reason why direct access to the connections used by Toplink JPA is required: for each connection I need to execute
- a "set role" to grant permissions,
- "set lock mode" to prevent hangups,
- "set isolation" to get the correct transaction type,
- possibly a "set explain on" to get query costs info,
- and a "set constraints all deferred" to have constraints checked at commit time, not earlier.
Can the Toplink pooling mechanism be replaced?

Answer 1

You can use either an external data source from your container or an JDBC data source for that matter but you cannot replace the internal connection pool. Although one option may be to use a wrapped connection pool of your own I would first recommend looking at the SessionEventListener callbacks. Implementing this interface and registering it using a SessionCustomizer (persistence unit property) would allow you to be notified and get access to the JDBC connection when acquired and released from either pooling mechanism.
Here is an example:
public class JDBCConnectionListener extends SessionEventAdapter implements SessionCustomizer {
     * This method is used when this class is configured as the session customizer
     * in the persistence unit properties.
    public void customize(Session session) {
        session.getEventManager().addListener(this);
     * This event is raised after a connection is acquired from a connection pool.
    public void postAcquireConnection(SessionEvent event) {
        DatabaseAccessor da = (DatabaseAccessor)event.getResult();
        Connection con = da.getConnection();
        PreparedStatement statement;
        try {
            event.getSession().log(SessionLog.FINE, SessionLog.SQL, "POST-ACQUIRE> SELECT SYSDATE FROM DUAL");
            statement = con.prepareStatement("SELECT SYSDATE FROM DUAL");
            ResultSet rs = statement.executeQuery();
            rs.close();
        } catch (SQLException e) {
            // TODO
     * This event is raised before a connection is released into a connection pool.
    public void preReleaseConnection(SessionEvent event) {
}Doug