O'Reilly - Java Message Service

4.1.1 Running the B2B Application
Java Message Service
Before looking at the code, let's look at how the application works. As with the Chat
application, the Wholesaler class includes a main( ) method so it can be run as a
standalone Java application. It's executed from the command line as follows:
java chap4.B2B.Wholesaler localhost username password
username and password are the authentication information for the client. The Retailer
class can be executed in the same manner:
java chap4.B2B.Retailer localhost username password
Start your JMS server, then run one instance of a Wholesaler client and a Retailer client in
separate command windows. In the Wholesaler client you are prompted to enter an item
description, an old price, and a new price. Enter the following as shown:
Bowling Shoes, 100.00, 55.00
Upon hitting the Enter key, you should see the Retailer application display information on
the screen indicating that it has received a price change notice. You should then see the
Wholesaler indicating that it has received a "buy" order from the Retailer. Here's the
complete interaction with the Wholesaler and the Retailer: [1]
[1] WHOLESALER and RETAILER are usernames you have set up when configuring your JMS
server. passwd1 and passwd2 are the passwords you've assigned to those usernames. If you are
using an evaluation version of a JMS provider, it may not be necessary to set up usernames and
passwords; check your vendor's documentation for more information.
java chap4.B2B.Wholesaler localhost WHOLESALER passwd1
Enter: Item, Old Price, New Price
e.g., Bowling Shoes, 100.00, 55.00
Bowling Shoes, 100.00, 55.00
Order received - 1000 Bowling Shoes from DurableRetailer
-----------------------
java chap4.B2B.Retailer localhost RETAILER passwd2
Retailer application started.
Received Hot Buy: Bowling Shoes, 100.00, 55.00
Buying 1000 Bowling Shoes
Here's what happened. The Wholesaler publishes a price quotation on a topic, "Hot Deals,"
which is intended for one or more Retailers. The Retailers subscribe to the "Hot Deals"
topic in order to receive price quotes. The Retailer application has no interaction with a
live user. Instead, it has an autoBuy( ) method that examines the old price and the new
price. If the new price represents a reduction of greater than ten percent, the Retailer
sends a message back to the Wholesaler on the "Buy Order" topic, telling it to purchase
1,000 items. In JMS terms, the Wholesaler is a producer of the "Hot Deals" topic and a
consumer of the "Buy Order" topic. Conversely, the Retailer is a consumer of the "Hot
Deals" topic and a producer of the "Buy Order" topic, as illustrated in Figure 4.1.
54