ProcessInstanceId as a variable

[ykphuah]

I have a start action that have a form, which I start using startProcessInstanceByKey. The next in the flow is an email task. I want to attach the ProcessInstanceId (as sort of a request id) in the subject of the email task.

I have tried using ${processInstanceId} but it says its an invalid variable.
I can't find a way to set the processInstanceId as a variable after I have started it.

Is there any other recommendation to have a unique "request id" for each process?

[ollib]

try ${execution.processInstanceId}

http://activiti.org/userguide/index.html#apiExpressions

[ykphuah]

Thanks! Worked perfect. Missed out that section of the user guide.