null pointer exception when finishing user task

chrisokelly — Wed, 27 Jun 2012 03:09:20 GMT

Hi,I know I have posted several topics in this forum in the past few days, so sorry for what may be seen by some as spam. I am attempting to create an advanced workflow in activiti to manage document expiry.I have removed most of the actual logic from the definition, replacing it with log messages s

Re: null pointer exception when finishing user task

chrisokelly — Thu, 28 Jun 2012 02:38:11 GMT

Got this solved now. The issue here came from a basic misunderstanding of what is meant by a border event, but some reading on the activiti website cleared things up. Boundary timers should not be attached to script tasks, essentially because the script task finishes and then tries to progress to the next task pretty much immediately (if I understand correctly), which causes the timer not to be persisted properly. I was using boundary timer events connected to script tasks where I wanted the workflow to wait without leaving a user task about. What I didn't know (mainly, I suppose, because the only workflow I had seen which used timed events at all was the one in Jeff Potts tutorial, which IS a boundary timer event, correctly attached to a user task) was that there is also a intermediate timer event, which is exactly what I wanted - ie progress to x point, wait until y then proceed. I kept a text file of some of the stupid mistakes I made coming up with my first workflow and some of what I learnt, so, on the off-chance someone will arrive here from google with the same or similar issues (hello future people! I am talking across time!) here it is-

Workflows - A learning experience:

When referring to groups (ie - for pooled tasks), the group identifier listed in the admin console is NOT the group authority. The group should be referred to by the group authority: "GROUP_{groupIdentifier}". If I add a group, with display name corporate and identifier GROUP_corporate, I still need to refer to it with GROUP_GROUP_corporate

it appears digits (0-9) in the ID field of a workflow element invalidate the XML and prevent alfresco from parsing the workflow.

In general, boundary timers should ONLY be connected to user tasks, and then only if there is another flow for the user to follow on completing the task manually.if attached to a script task, you will see a Java.lang.nullPointerException. the correct usage is - timer set to cancel action: true (if the user does not act before x time continue to y task), even then there should almost always be another flow available for the user to follow if they DO act before x time.

Every once in a while in the eclipse graphical editor, the Exclusive gateway element decides to add an empty default property (unless you have specified a default flow already). This causes the xml to be invalid and alfresco will not start on deployment. Open the bpmn (or bpmn20.xml) file with a text editor and remove default=''.

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null pointer exception when finishing user task

Re: null pointer exception when finishing user task