Decoupling the Database Adapter Service

In the previous section, we saw how the Mediator has decoupled the PatientAppointmentService from the File Adapter Service. AppointmentRequests that are received by the File Adapter Service are still passed to the PatientAppointmentService. However, changes in the filenaming convention or the record structure do not have any impact on the PatientAppointmentService and the BPEL process that implements it. It does not even matter to the service if we introduce alternative channels for receiving appointment requests, such as a database to have them created from a web application, an FTP server, or a JMS queue: The Mediator insulates the PatientAppointmentService from such new developments. Of course, this may lead to changes in the Mediator—the routing rules or mappings—but such changes are fairly easy to apply.

We would like to achieve the same level of decoupling for the outgoing calls to the Database Adapter Services from the PatientDataService BPEL process.