TaskMgmtSession.findTaskInstancesByIds() fails if taskInstanceIds is an empty list

org.jbpm.command.GetTaskListCommand.execute() throws JbpmPersistenceException if there is no pooled task instances for a given actor even if the actor has personally assigned task instaces.

=====
org.jbpm.persistence.JbpmPersistenceException: couldn't get task instances by ids '[]'
at org.jbpm.db.TaskMgmtSession.findTaskInstancesByIds(TaskMgmtSession.java:204)
at org.jbpm.db.TaskMgmtSession.findPooledTaskInstances(TaskMgmtSession.java:123)
at org.jbpm.JbpmContext.getGroupTaskList(JbpmContext.java:194)
at org.jbpm.command.GetTaskListCommand.execute(GetTaskListCommand.java:54)
at sample.task.ws.TaskSampleWS.test(TaskSampleWS.java:52)
=====

In case of CP01, GetTaskListCommand returns the personal task list without Exception.

This behavior is caused by the change introduced by r4076 in org.jbpm.db.TaskMgmtSession.findTaskInstancesByIds().

r4705
===
public List<TaskInstance> findTaskInstancesByIds(List<Long> taskInstanceIds) {
List<TaskInstance> result;
if (taskInstanceIds.isEmpty())

{ result = Collections.emptyList(); }

else {
try

{ Query query = session.getNamedQuery("TaskMgmtSession.findTaskInstancesByIds"); query.setParameterList("taskInstanceIds", taskInstanceIds); result = CollectionUtil.checkList(query.list(), TaskInstance.class); }

catch (Exception e)

{ handle(e); throw new JbpmException("couldn't get task instances by ids '" + taskInstanceIds + "'", e); }

}
return result;
}
===

r4706
===
public List findTaskInstancesByIds(List taskInstanceIds) {
try

{ return session.getNamedQuery("TaskMgmtSession.findTaskInstancesByIds") .setParameterList("taskInstanceIds", taskInstanceIds) .list(); }

catch (HibernateException e)

{ handle(e); throw new JbpmPersistenceException("couldn't get task instances by ids '" + taskInstanceIds + "'", e); }

}
===

The change was related to JBPM-2205 and removed the empty check because the method Collections.emptyList() is not supported in jdk1.4. But I think an equivalent empty check should be restored.