O'Reilly - Java Message Service

Java Message Service
uses a JMS transaction either to place all of the orders (commit) or to cancel them
(rollback).
Before getting into the details of the example, run the version of the wholesaler and retailer
applications in this chapter. Start the Wholesaler and Retailer applications in separate
command windows:
java chap6.Wholesaler localhost username password
java chap6.Retailer localhost username password
First, we will study the case in which all the prices are acceptable. We start with acceptable
price reductions for both items. When prompted by the Wholesaler application, enter:
Surfboards, 999.99, 499.99
Wetsuits, 299.99, 149.99
When you enter these new prices, the Retailer should indicate that it is purchasing 1000
surfboards. You shouldn't see anything in the Wholesaler window to indicate that it
received the order, because the Retailer is using a transacted session to send the "Buy
Order" messages. The Wholesaler won't receive the message until the Retailer commits
the session. Now go back to the Wholesaler and type "end".
While the Retailer is using transactions in this example, the Wholesaler is not. When you
type in the word "end" on the command line, Wholesaler sends a message to Retailer
indicating that it is finished with its group of messages, as shown in this excerpt from
Wholesaler's command-line processing loop:
...
while ( true ){
String dealDesc = stdin.readLine( );
if ( dealDesc != null && dealDesc.length( ) > 0 ){
if ( dealDesc.substring(0,3).equalsIgnoreCase("END") ){
wholesaler.sendSequenceMarker( "END_SEQUENCE" );
} else {
...
Wholesaler.sendSequenceMarker( ) simply creates a message, sets a property on it, and
publishes it:
private void sendSequenceMarker(String sequenceMarker){
try {
javax.jms.StreamMessage message = session.createStreamMessage( );
message.setStringProperty("SEQUENCE_MARKER",sequenceMarker);
}
publisher.publish(
message,
javax.jms.DeliveryMode.PERSISTENT,
javax.jms.Message.DEFAULT_PRIORITY,
1800000);
} catch ( javax.jms.JMSException jmse ){
jmse.printStackTrace( );
}
This message has no body. We set the user-defined property "SEQUENCE_MARKER", which the
receiving application uses to know when the group of "Hot Deals" messages is completed.
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