Advanced Queuing - Oracle

Propagation Features
Note that AQ does not support propagation from Object queues that have BFILE or
REF attributes in the payload.
Scenario
In the BooksOnLine application, the company may wish to send promotional
coupons along with the book orders. These coupons are generated depending on
the content of the order, and other customer preferences. The coupons are images
generated from some multimedia database, and are stored as LOBs.
When the order information is sent to the shipping warehouses, the coupon
contents are also sent to the warehouses. In the following code, order_typ is
enhanced to contain a coupon attribute of LOB type. The code demonstrates how
the LOB contents are inserted into the message that is enqueued into OE_
bookedorders_que when an order is placed. The message payload is first
constructed with an empty LOB. The place holder (LOB locator) information is
obtained from the queue table and is then used in conjunction with the LOB
manipulation routines, such as DBMS_LOB.WRITE(), to fill the LOB contents. The
example has additional examples regarding for enqueue and dequeue of messages
with LOBs as part the payload.
A COMMIT is issued only after the LOB contents are filled in with the appropriate
image data. Propagation automatically takes care of moving the LOB contents along
with the rest of the message contents. The following code also shows a dequeue at
the destination queue for reading the LOB contents from the propagated message.
The LOB contents are read into a buffer that can be sent to a printer for printing the
coupon.
PL/SQL (DBMS_AQADM Package): Example Code
/* Enhance the type order_typ to contain coupon field (lob field): */
CREATE OR REPLACE TYPE order_typ AS OBJECT (
orderno NUMBER,
status VARCHAR2(30),
ordertype VARCHAR2(30),
orderregion VARCHAR2(30),
customer customer_typ,
paymentmethod VARCHAR2(30),
items orderitemlist_vartyp,
total NUMBER,
coupon BLOB);
/
/* lob_loc is a variable of type BLOB,
buffer is a variable of type RAW,
8-112 Oracle9i Application Developer’s Guide - Advanced Queuing