In this chapter, we have learned about different types of events and managing the events from BPEL processes within the SOA environment. We have explained the events and the difference between the event-driven approach and operation invocations. We have briefly mentioned the Event Driven Architecture. We have learned that a BPEL process can react on business events, message events, and alarm events. Business events are events with a well-defined business meaning, which are explicitly triggered by a process, service, or other software component. Message events are triggered by operation invocations on port types. Alarm events are triggered by deadline or duration expressions.

A BPEL process can be event-driven, which means that it will be triggered by a business event. A BPEL process can also trigger a business event, which will result in executing all processes, services, and other components subscribed to this type of event.

A BPEL process can react on events using event handlers. Event handlers monitor the specified message or alarm events simultaneously while the BPEL process is executing. This enables a BPEL process to react on events such as cancelation messages or timeouts.

A BPEL process can also react on events in asynchronous invocations. When waiting for callbacks, it is often useful to use the <pick> activity to be able to wait for different messages and for alarm events.

Now that you have learned how to handle events, we move ahead to learn about compensations.