Associate a Conversation with a Process Instance

When resolving @BusinessProcessScoped beans, or injecting process variables, we rely on an existing association between an active CDI scope and a process instance. camunda-engine-cdi provides the org.camunda.bpm.engine.cdi.BusinessProcess bean for controlling the association, most prominently:

• the startProcessBy*(…)-methods, mirroring the respective methods exposed by the RuntimeService allowing to start and subsequently associate a business process,
• resumeTaskById(String taskId), allowing to associate the task with the provided Id (and by extension, the corresponding process instance).
  Once a unit of work (for example a UserTask) is completed, the completeTask() method can be called to disassociate the conversation/request from the process instance. This signals the engine that the current task is completed and makes the process instance proceed.

Note that the BusinessProcess-bean is a bean, which means that the exposed methods can be invoked using expression language, for example from a JSF page. The following JSF2 snippet begins a new conversation and associates it with a user task instance, the Id of which is passed as a request parameter (e.g., ):

Declaratively Controlling the Process

Depending on the configuration of the Camunda engine, the code of the annotated method and the starting of the process instance will be combined in the same transaction. The -annotation works in the same way:

The annotation offers the possibility to end the current conversation. The default behavior is to end the conversation after the call to the engine returns. Ending the conversation can be disabled, as shown in the example above.

Work with @BusinessProcessScoped Beans

Sometimes, we want to work with process scoped beans, in the absence of an association with a process instance, for example before starting a process. If no process instance is currently active, instances of BusinessProcessScoped beans are temporarily stored in a local scope (i.e., the Conversation or the Request, depending on the context.). If this scope is later associated with a business process instance, the bean instances are flushed to the process instance.