How to "unget" an instance via Papi from External Interactive activity?

Question

Using ALBPM5.7, am trying to create a java app to implement an external interactive activity following this general process:
1. poll for next "gettable" instance in desired process/task (in order of priority, receivedtime)
2. call Get the instance to reserve it to current user
3. call prepareExternalActivity for instance to get arguments from FBL
4. do some work on the instance
5. call commitExternalActivity to pass args back in to FBL
I have created something like the following code snippet based sample code from the PAPI docs:
// get the instance to be worked, assumes previously found the "next" one based on priority/recievedtime to variable ii
Filter filter = ProcessService.createFilter();
filter.setSearchScope(new SearchScope(ParticipantScope.ALL, StatusScope.ALL, null));
filter.addAttribute(VarDefinition.getDefaultVarDefinition(VarDefinition.INSTANCE_NUMBER), Comparison.IS, ii.getInstanceIn());
InstanceInfo[] instances = new InstanceInfo[0];
instances = papiSession.getInstancesByFilter( new String[] { processId }, filter );
if ( instances.length == 0 ) return null;
Arguments arguments = Arguments.create();
arguments = session.prepareExternalActivity(instance.getId(), instance.getActivityName(), Arguments.create());
String info = (String) arguments.getArgument("preArgOut");
// do some work...
arguments = Arguments.create();
arguments.putArgument("comArgIn", info);
session.commitExternalActivity(instance.getId(), instance.getActivityName(), arguments);
I have a question, though. If, during the "do some work" step the user cannot finish for any reason, how do I cancel the "get" (or "unget" it) on the instance so that it remains in the same activity for the next user to work?
Thanks,
Todd

Answer 1

More info...
If I dump the instanceInfo object (converted to xml using the com.thoughtworks.xstream library), I get the xml below. While the Status shows as 1 (=Running), the isExecuting is "false". For this same instance (ii), since there is only one task (TaskIn=0), the call to abortActivity is:
papiSession.abortActivity(ii.getId(), ii.getActivityName(), 0);
Which yields the "Instance '/ExtInterTest#Default-1.2/110619/0' is not running." exception.
I have previously "selected" the instance prior to calling prepareExternalActivity, but at this point instanceCanBeUnselected(ii) is false.
...not sure what to try next. Is there possibly some way to raise an exception from the papi client back to the engine that would allow me to abort the activity from within the process flow (e.g. just put it back to available at the ExternalInteractive activity that was not completed)?
------------------------ xml dump of instanceInfo object ------------------------
<fuego.papi.impl.InstanceInfoImpl>
<instanceIn__d>110619</instanceIn__d>
<processIn__d>229</processIn__d>
<threadIn__d>0</threadIn__d>
<creationTime__d>
<microSeconds__d>1240499309197000</microSeconds__d>
</creationTime__d>
<roleId>Unattended</roleId>
<HIGH>4</HIGH>
<HIGHEST>5</HIGHEST>
<LOW>2</LOW>
<LOWEST>1</LOWEST>
<NORMAL>3</NORMAL>
<activityName__d>Task1</activityName__d>
<author__d>-1</author__d>
<cThreads>0</cThreads>
<description__d>ExtInterTest110619</description__d>
<externalVariables__d>
<long>110619</long>
<string></string>
</externalVariables__d>
<internalState__d>12289</internalState__d>
<isExecuting__d>false</isExecuting__d>
<nAttachments>0</nAttachments>
<nNotes>0</nNotes>
<nThreads__d>0</nThreads__d>
<numberOfChanges>105</numberOfChanges>
<parentThreadIn__d>-1</parentThreadIn__d>
<participantIn__d>0</participantIn__d>
<pendingTaskIn__d>-1</pendingTaskIn__d>
<priority__d>3</priority__d>
<receptionTime__d>
<microSeconds__d>1240508930000000</microSeconds__d>
</receptionTime__d>
<roleIn__d>50000496</roleIn__d>
<status__d>1</status__d>
<taskInfo__d>
<fuego.papi.impl.InstanceInfoImpl_-TaskInfo>
<participantId__d>unattended</participantId__d>
<retryCounter__d>0</retryCounter__d>
<status__d>48</status__d>
<taskIn__d>0</taskIn__d>
<valid__d>true</valid__d>
</fuego.papi.impl.InstanceInfoImpl_-TaskInfo>
</taskInfo__d>
</fuego.papi.impl.InstanceInfoImpl>