Patterns: Implementing Self-Service in an SOA Environment

Chapter 11. JMS scenario 363

򐂰 Enterprise Service Bus

The ESB is implemented using the service integration bus. The bus provides

the transport mechanism for the default messaging provider. Messages sent

to MailService are placed on a queue defined to the bus. A mediation will be

added to transform the format of the message payload from text to XML. This

mediation activity is transparent to the applications. If, in the future, a different

mail service is used and it requires something other than XML, the only

change required is in the mediation activity on the bus.

򐂰 Mail Sender

This component uses an EJB message-driven bean to receive the message

from the queue and the Java Mail API to send the e-mail to MailService.

򐂰 MailService

Our SMTP server, that sends the e-mail to the customer.

򐂰 XlateToXML

This component is a mediation application. When a message arrives at the

bus, this application transforms the message. The Mail Sender MDB receives

the transformed message.

This scenario illustrates the following application pattern using messaging

technology:

򐂰 Directly Integrated Single Channel application pattern

ITSOMart places a message on a queue. Mediation takes place to transform

the message into a new format. The Mail service retrieves the message and

sends an e-mail to the user.

11.2 System design overview

In this scenario, the ITSOMart application will be connected to an enterprise-tier

application (MailService) using JMS.

11.2.1 Component model

The ITSOMart will send a notification message to the customer when the

registration process is complete. The application does this by generating a JMS

message for MailService. The message contains the e-mail text to be sent.

MailService is expecting XML format so a mediation is added to the bus that

transforms the message to the proper format.

Figure 11-2 on page 364 shows the component model for the scenario.