topic Re: Dynamic assignment in Alfresco Archive

Dynamic assignment

hmartim — Wed, 06 Apr 2011 14:36:25 GMT

Hi,an excellent extension of the Activiti is the possibility of defining "activiti:assignee" and "activiti:candidateUsers" of a UserTask via a Spring bean operation like "$ {ldapService.findManagerForEmployee (loan)}" or "$ {ldapService.findAllSales ()}".This allows dynamic definition of resources f

Re: Dynamic assignment

frederikherema1 — Fri, 08 Apr 2011 08:25:18 GMT

Hi,

Nothing built in into the engine to re-calculate the assignee/candidates, only happens when task is created. You could however write your own logic that , when manager changes for example, you query all tasks that are assigned to that person (taskService.createTaskQuery().assignee("manager").list()) and update the assignee to the new one…

Re: Dynamic assignment

hmartim — Fri, 08 Apr 2011 13:25:08 GMT

That would be an interesting way if there was only one case to treat, as the example of the employee's manager. But there are several cases with different logics.

Since these logical, which can be complex, would be encapsulated in the called beans operations, the replay would be simpler than externally treat each event and update the internal structure of the Actitivi database.

Is there a way through the engine api to get the string definition for assignment (assignee or candidateUsers) of a UserTask? So, I could recover through the engine the unfinished tasks, retrieve that string definition of each task (like "ldapService.findManagerForEmployee(10)") and make this run externally.

Thanks,
Hudson.

Re: Dynamic assignment

frederikherema1 — Fri, 08 Apr 2011 13:37:02 GMT

You can get hold of the TaskDefinition, which contains an assigneeExpression. You can evaluate the assigneeExpression (Expression) with the ExpressionManager, against an VariableScope (eg. DelegateExecution). Not sure how you would handle this outside of activiti-context (when no execution is available)…

Bear in mind, TaskDefinition and it's expressions is all internal stuff so can't be 100% sure of backward compatibility

@see org.activiti.engine.impl.bpmn.behavior.UserTaskActivityBehavior.TaskDefinition
@see org.activiti.engine.impl.el.ExpressionManager

Re: Dynamic assignment

hmartim — Fri, 08 Apr 2011 14:23:02 GMT

I figured something like this:

Periodically (at night, for example), retrieve unfinished tasks with TaskService.createTaskQuery ().<…>. list()

For each task, retrieve the key of its definition with task.getTaskDefinitionKey()

Retrieve the task definition using the recovered key (How to do it via api?)

For tasks with a dynamic assignment, evaluate the assigneeExpression (Expression) with the ExpressionManager (How to do it via api?) and call the bean to retrieve the user in this new time.

If it was different from today's, update it via api.

This is correct?

Thanks.

Re: Dynamic assignment

frederikherema1 — Mon, 11 Apr 2011 07:28:20 GMT

That's indeed a way of doing this, without intruding into the engine. Getting the taskDefinition requires casting to impl classes:


ProcessDefinitionEntity procDef  = (ProcessDefinitionEntity) ((ReposityServiceImpl)repositoryService).getDeployedProcessDefinition(processDefinitionId);
tDef = procDef.getTaskDefinition("userTask");

No guarantees on backward compatibility

Re: Dynamic assignment

hmartim — Mon, 11 Apr 2011 17:03:36 GMT

I'll try this way then.

Thank you for your replies!

Re: Dynamic assignment

jsher — Thu, 16 Jun 2011 14:38:50 GMT

Hi

I would like to add a TaskListener to all tasks without having to require all process designers to specify the listener in xml, ie. a 'standard' task listener which will ensure that some standard behaviour for all user tasks, eg. notify creation of user task instances to various external listening apps/guis/etc

Getting access to the process definitions at runtime (as shown in previous replies) and adding our standard task listener seems like one way to do this, but as this relies on accessing Activiti internals I am wary of going down this route. A couple of questions then..
1. Is there a better way to do this ?
2. If not, how risky is it to rely on these 'internals' from point of view of future compatibility.

Thanks
James

Re: Dynamic assignment

frederikherema1 — Thu, 16 Jun 2011 14:47:20 GMT

Try the BPMNListener approach I suggested a while back… see:

http://forums.activiti.org/en/viewtopic.php?f=6&t=1189&p=4839&hilit=ParseListener#p4839

This way you can, on every task that is used in Activiti, add your listeners without having to define them on each and every process.

Re: Dynamic assignment

jsher — Thu, 16 Jun 2011 15:12:39 GMT

That's great -thanks Frederik.

Just to clarify my understanding of how this works… At process deployment time (ProcessRepository.deployProcess) the BPMN parser will invoke parseUserTask() for all registered BpmnParseListener's. The listener adds TaskListener and Activiti persists this along with the process definition. Is this how it goes ?

How to register the listener ? ProcessEngineConfigurationImpl.? - setPreParseListeners, setPostParseListeners, setCustomPreBPMNParseListeners, setCustomPostBPMNParseListeners ?

Regards
James

Re: Dynamic assignment

frederikherema1 — Fri, 17 Jun 2011 06:27:41 GMT

Yes, you're right, the parsers are applied when the process is deployed OR when it's fetched from the DB (when not in cache). So all process-definitions that are used by activiti are guaranteed to have these listeners applied…

The Pre and Post-methods control when the listeners are called: before the activiti-ones or after (eg. a lot of the history is done using parseListeners). Both setXXParseListener and setCustomXXXBPMNParseLIsteners will work.

Re: Dynamic assignment

heymjo — Fri, 17 Jun 2011 14:00:50 GMT

this is a very interesting extension point so i was trying it out :


public class AssignmentCheckParseListener implements BpmnParseListener{
…
    public void parseUserTask(Element userTaskElement, ScopeImpl scope, ActivityImpl activity) {
        activity.addExecutionListener(TaskListener.EVENTNAME_ASSIGNMENT, new ExecutionListener() {
            public void notify(DelegateExecution execution) throws Exception {
                System.out.println("@@@@@@@@@@@@" + execution.getId());
            }
        });
    }
….

and my spring configuration bean


    ….
    <property name="preParseListeners">
      <util:list>
        <bean class="my.AssignmentCheckParseListener"/>
      </util:list>
    </property>
  </bean>

From debug stepping i see that my parselistener is invoked correctly for each user task in the workflow. But during execution, the executionlistener is not fired when the task gets claimed, odd.

Also, would such an executionlistener be the proper way of re-checking the candidate groups at the moment of assignment ? My aim is to throw an exception when the task is picked up by a user who no longer is part of the task's candidategroup.

Re: Dynamic assignment

heymjo — Fri, 17 Jun 2011 14:27:47 GMT

<yawn> ignore my post it's friday afternoon.

the correct way to add the tasklistener is this


    public void parseUserTask(Element userTaskElement, ScopeImpl scope, ActivityImpl activity) {
        TaskDefinition taskDefinition = ((UserTaskActivityBehavior) activity.getActivityBehavior()).getTaskDefinition();

        taskDefinition.addTaskListener(TaskListener.EVENTNAME_ASSIGNMENT,
                new TaskListener() {
                    public void notify(DelegateTask delegateTask) {
                        System.out.println("@@@@@@@@@@@@@" + delegateTask.getName());
                    }
                });
    }

Re: Dynamic assignment

ronald_van_kuij — Sun, 19 Jun 2011 10:07:59 GMT

Thanks for investigating this yourself a little more AND reporting back (after getting it to work) wished that more people would do this.

Re: Dynamic assignment

frederikherema1 — Mon, 20 Jun 2011 12:22:46 GMT

Glad it works!