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: