NPE when completing task with non-null assignee

[rhafner]

I'm hitting a NPE when attempting to complete a task after claiming it with a non-null userId on version 5.13.

Example:
taskService.claim(taskId, "user1");
taskService.complete(taskId);

Digging into the source a bit I see the following comment in GetIdentityLinksForTaskCmd. java suggesting this might be a known issue. However, I was unable to find an issue in JIRA for it.

    // assignee is not part of identity links in the db.
    // so if there is one, we add it here.
    // @Tom: we discussed this long on skype and you agreed 😉
    // an assignee *is* an identityLink, and so must it be reflected in the API
    //
    // Note: we cant move this code to the TaskEntity (which would be cleaner),
    // since the task.delete cascased to all associated identityLinks
    // and of course this leads to exception while trying to delete a non-existing identityLink

The NPE occurs because GetIdentityLinksForTaskCmd.java creates an ASSIGNEE IdentityLink with a null id when a Task's assignee property is not null. This IdentityLink is then passed to DbSqlSession.delete which performs a sameIdentity() check on the IdentityLink resulting in a NPE on the equals call due to persistentObject.getId() being null.

DbSqlSession.java
    @Override
    public boolean sameIdentity(PersistentObject other) {
      return persistentObject.getClass().equals(other.getClass())
          && persistentObject.getId().equals(other.getId());
    }

Some questions:
1) Has there been any further discussion regarding this issue?
2) Is there a resolution?
3) Any reason null id's can't be considered different for the sameIdentity check?

Including the full StackTrace for reference:

java.lang.NullPointerException
   at org.activiti.engine.impl.db.DbSqlSession$CheckedDeleteOperation.sameIdentity(DbSqlSession.java:209)
   at org.activiti.engine.impl.db.DbSqlSession.delete(DbSqlSession.java:134)
   at org.activiti.engine.impl.persistence.entity.IdentityLinkEntityManager.deleteIdentityLink(IdentityLinkEntityManager.java:31)
   at org.activiti.engine.impl.persistence.entity.IdentityLinkEntityManager.deleteIdentityLinksByProcInstance(IdentityLinkEntityManager.java:89)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.removeIdentityLinks(ExecutionEntity.java:1226)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.remove(ExecutionEntity.java:839)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationProcessEnd.eventNotificationsCompleted(AtomicOperationProcessEnd.java:62)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:56)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:49)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationActivityEnd.eventNotificationsCompleted(AtomicOperationActivityEnd.java:54)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:56)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:49)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.end(ExecutionEntity.java:340)
   at org.activiti.engine.impl.bpmn.behavior.NoneEndEventActivityBehavior.execute(NoneEndEventActivityBehavior.java:24)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationActivityExecute.execute(AtomicOperationActivityExecute.java:44)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionNotifyListenerStart.eventNotificationsCompleted(AtomicOperationTransitionNotifyListenerStart.java:52)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:56)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:49)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionCreateScope.execute(AtomicOperationTransitionCreateScope.java:49)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionNotifyListenerTake.execute(AtomicOperationTransitionNotifyListenerTake.java:66)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionDestroyScope.execute(AtomicOperationTransitionDestroyScope.java:116)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionNotifyListenerEnd.eventNotificationsCompleted(AtomicOperationTransitionNotifyListenerEnd.java:36)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:56)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.pvm.runtime.AbstractEventAtomicOperation.execute(AbstractEventAtomicOperation.java:49)
   at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:87)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:532)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:527)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.take(ExecutionEntity.java:367)
   at org.activiti.engine.impl.bpmn.behavior.BpmnActivityBehavior.performOutgoingBehavior(BpmnActivityBehavior.java:105)
   at org.activiti.engine.impl.bpmn.behavior.BpmnActivityBehavior.performDefaultOutgoingBehavior(BpmnActivityBehavior.java:54)
   at org.activiti.engine.impl.bpmn.behavior.FlowNodeActivityBehavior.leave(FlowNodeActivityBehavior.java:44)
   at org.activiti.engine.impl.bpmn.behavior.AbstractBpmnActivityBehavior.leave(AbstractBpmnActivityBehavior.java:47)
   at org.activiti.engine.impl.bpmn.behavior.UserTaskActivityBehavior.signal(UserTaskActivityBehavior.java:96)
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.signal(ExecutionEntity.java:350)
   at org.activiti.engine.impl.persistence.entity.TaskEntity.complete(TaskEntity.java:160)
   at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:39)
   at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:24)
   at org.activiti.engine.impl.cmd.NeedsActiveTaskCmd.execute(NeedsActiveTaskCmd.java:61)
   at org.activiti.engine.impl.interceptor.CommandExecutorImpl.execute(CommandExecutorImpl.java:24)
   at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:61)
   at org.activiti.spring.SpringTransactionInterceptor$1.doInTransaction(SpringTransactionInterceptor.java:42)
   at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:130)
   at org.activiti.spring.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:40)
   at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:31)
   at org.activiti.engine.impl.TaskServiceImpl.complete(TaskServiceImpl.java:163)

[frederikherema1]

Can you please provide the context in which the 2 service-calls are done? Our test-suite covers the use case (having an assignee on a task an completing it) like a million times, so it' definitely not a bug that is always reproduced.

Do you call the claim(…) and complete(..) from within a task-listener? By the way, the exception is coming from the "delete" of an identity-link  on a process-instance, not on the task itself… So more context is needed to analyze why this is happening…

[mederly]

I've come across the same problem today. As you suggested, in my case it occurs when calling taskService.getIdentityLinksForTask(…) while processing completion event in the task listener.

I've created an issue for that: http://jira.codehaus.org/browse/ACT-2001 along with test case to demonstrate the problem.

[vigneshbhaskar]

Hi Mederly, Is this issue raised by you resolved? I upgraded my activiti from 5.12 to 5.15 and everything is breaking down. I am encountering the same issue which you have raised while trying to complete a task. The task has an attached listener which triggers my custom method named persistIdentityLink when the task is completed.


<java>

Exception in thread "main" java.lang.NullPointerException
at org.activiti.engine.impl.db.DbSqlSession$CheckedDeleteOperation.sameIdentity(DbSqlSession.java:252) at org.activiti.engine.impl.db.DbSqlSession$CheckedDeleteOperation.sameIdentity(DbSqlSession.java:252)
at org.activiti.engine.impl.db.DbSqlSession.removeUnnecessaryOperations(DbSqlSession.java:519)
at org.activiti.engine.impl.db.DbSqlSession.flush(DbSqlSession.java:483)
at org.activiti.engine.impl.interceptor.CommandContext.flushSessions(CommandContext.java:175)
at org.activiti.engine.impl.interceptor.CommandContext.close(CommandContext.java:122)
at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:66)
at org.activiti.spring.SpringTransactionInterceptor$1.doInTransaction(SpringTransactionInterceptor.java:47)
at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:131)
at org.activiti.spring.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:45)
at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:37)
at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:40)
at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:35)
at org.activiti.engine.impl.TaskServiceImpl.complete(TaskServiceImpl.java:166)
at TestingActiviti.main(TestingActiviti.java:66)
at org.activiti.engine.impl.db.DbSqlSession$CheckedDeleteOperation.sameIdentity(DbSqlSession.java:252)
</java>

[martin_grofcik]

Hi,

I checked out activiti-5.15 from git. org.activiti.engine.impl.db.DbSqlSession$CheckedDeleteOperation.sameIdentity(DbSqlSession.java:252) is empty line. Do you really use 5.15.

Regards
Martin