Advanced Queuing - Oracle

}
Message Grouping
}
catch (Exception ex)
{
System.out.println("Exception :" + ex);
}
Enqueue Features
Messages belonging to one queue can be grouped to form a set that can only be
consumed by one user at a time. This requires that the queue be created in a queue
table that is enabled for transactional message grouping (see "Creating a Queue
Table" on page 9-4 in Chapter 9, "Administrative Interface"). All messages belonging
to a group have to be created in the same transaction and all messages created in
one transaction belong to the same group. With this feature, you can segment
complex messages into simple messages.
For example, messages directed to a queue containing invoices can be constructed
as a group of messages starting with the header message, followed by messages
representing details, followed by the trailer message. Message grouping is also
useful if the message payload contains complex large objects such as images and
video that can be segmented into smaller objects.
The general message properties (priority, delay, expiration) for the messages in a
group are determined solely by the message properties specified for the first
message (head) of the group, irrespective of which properties are specified for
subsequent messages in the group.
The message grouping property is preserved across propagation. However, it is
important to note that the destination queue where messages have to be propagated
must also be enabled for transactional grouping. There are also some restrictions
you need to keep in mind if the message grouping property is to be preserved while
dequeuing messages from a queue enabled for transactional grouping (see
"Dequeue Methods" on page 8-58 and "Modes of Dequeuing" on page 8-69 for
additional information).
Scenario
In the BooksOnLine application, message grouping can be used to handle new
orders. Each order contains a number of books ordered one by one in succession.
Items ordered over the Web exhibit similar behavior.
In the following example, each enqueue corresponds to an individual book that is
part of an order and the group/transaction represents a complete order. Only the
A Sample Application Using AQ 8-51