19.3. Creating Transactional Web Services

A participant is a software entity which is driven by the transaction manager on behalf of a Web service. When a web service wants to participate in a particular transaction, it must enroll a participant to act as a proxy for the service in subsequent negotiations with the coordinator. The participant implements an API appropriate to the type of transaction it is enrolled in, and the participant model selected when it is enrolled. For example, a Durable2PC participant, as part of a WS-Atomic Transaction, implements the Durable2PCParticipant interface. The use of participants allows the transactional control management aspects of the Web service to be factored into the participant implementation, while staying separate from the the rest of the Web service's business logic and private transactional data management.

The creation of participants is not trivial, since they ultimately reflect the state of a Web service’s back-end processing facilities, an aspect normally associated with an enterprise’s own IT infrastructure. Implementations must use one of the following interfaces, depending upon the protocol it will participate within: com.arjuna.wst11.Durable2PCParticipant, com.arjuna.wst11.Volatile2PCParticipant, com.arjuna.wst11.BusinessAgreementWithParticipantCompletionParticipant, or com.arjuna.wst11.BusinessAgreementWithCoordinatorCompletionParticipant.