Advanced Queuing - Oracle

Dequeue Features
}
Exception Handling
/* Dequeue the message */
message = bookedorders_q.dequeue(deq_option, Order.getFactory());
obj_payload = message.getObjectPayload();
deq_order = (Order)(obj_payload.getPayloadData());
/* for simplicity, assume order has a single item */
order_item = deq_order.getItems().getElement(0);
book = order_item.getItem();
/* assume search_inventory searches inventory for the book
* if we don't find the book in the warehouse, abort transaction
*/
if(search_inventory(book) != true)
db_conn.rollback();
else
process_order(deq_order);
}
catch (AQException aqex)
{
System.out.println("Exception-1: " + aqex);
}
catch (Exception ex)
{
System.out.println("Exception-2: " + ex);
}
AQ provides four integrated mechanisms to support exception handling in
applications: EXCEPTION_QUEUES, EXPIRATION, MAX_RETRIES and RETRY_
DELAY.
An exception_queue is a repository for all expired or unserviceable messages.
Applications cannot directly enqueue into exception queues. Also, a multiconsumer
exception queue cannot have subscribers associated with it. However, an
application that intends to handle these expired or unserviceable messages can
dequeue from the exception queue. The exception queue created for messages
intended for a multiconsumer queue must itself be a multiconsumer queue. Like
any other queue, the exception queue must be enabled for dequeue using the
8-80 Oracle9i Application Developer’s Guide - Advanced Queuing