O'Reilly - Java Message Service

Java Message Service
When a JMS consumer declares a message selector for a particular
destination, the selector is applied only to messages delivered to that
consumer. Every JMS client can have a different selector specified
for each of its consumers.
What happens to messages that are not selected for delivery to the consumer by its
message selector? This depends on the message model used. In the pub/sub model, the
message is simply not delivered to that consumer, but it is delivered to other consumers.
This is true of both nondurable and durable subscriptions. In the p2p model, the messages
remain in the queue, so other consumers of the queue can see them, but they are not visible
to the consumer that used the message selector.
3.3.1 Message Selector Examples
Here are three complex selectors used in hypothetical environments. Although you will
have to use your imagination a little, the purpose of these examples is to convey the power
of the message selectors. When a selector is declared, the identifier always refers to a
property name or JMS header name in the message. For example, the selector "'username
!= 'William'" assumes that there is a property in the message named username, which can
be compared to the value 'William'.
Managing claims in an HMO
Due to some fraudulent claims, an automatic process is implemented that will audit
all claims submitted by patients who are employees of the ACME manufacturing
company with visits to chiropractors, psychologists, and dermatologists:
String selector =
"PhysicianType IN ('Chiropractor', 'Psychologist', 'Dermatologist') "
+ "AND PatientGroupID LIKE 'ACME%'";
TopicSubscriber subscriber =
session.createSubscriber(topic, selector,false);
Selecting recipients for a catalog mailing
An online retailer wants to deliver a special catalog to any customer that orders more
then $500.00 worth of merchandise where the average price per item ordered is
greater than $75.00 and the customer resides in one of several states. The retailer
creates a special application that subscribes to the order processing topic and
processes catalog deliveries for only those customers that meet the defined criteria:
String selector =
"TotalCharge > 500.00 AND ((TotalCharge / ItemCount) >= 75.00) "
+ "AND State IN ('MN', 'WI', 'MI', 'OH')";
TopicSubscriber subscriber =
session.createSubscriber(topic, selector,false);
41