Custom command to go back in a process instance (execution) - back

Question

I have a process where I have 3 sequential user tasks (something like Task 1 -> Task 2 -> Task 3). So, to validate the Task 3, I have to validate the Task 1, then the Task 2.
My goal is to implement a workaround to go back in an execution of a process instance thanks to a Command like suggested in this link. The problem is I started to implement the command by it does not work as I want. The algorithm should be something like:
Retrieve the task with the passed id
Get the process instance of this task
Get the historic tasks of the process instance
From the list of the historic tasks, deduce the previous one
Create a new task from the previous historic task
Make the execution to point to this new task
Maybe clean the task pointed before the update
So, the code of my command is like that:
public class MoveTokenCmd implements Command<Void> {
protected String fromTaskId = "20918";
public MoveTokenCmd() {
}
public Void execute(CommandContext commandContext) {
HistoricTaskInstanceEntity currentUserTaskEntity = commandContext.getHistoricTaskInstanceEntityManager()
.findHistoricTaskInstanceById(fromTaskId);
ExecutionEntity currentExecution = commandContext.getExecutionEntityManager()
.findExecutionById(currentUserTaskEntity.getExecutionId());
// Get process Instance
HistoricProcessInstanceEntity historicProcessInstanceEntity = commandContext
.getHistoricProcessInstanceEntityManager()
.findHistoricProcessInstance(currentUserTaskEntity.getProcessInstanceId());
HistoricTaskInstanceQueryImpl historicTaskInstanceQuery = new HistoricTaskInstanceQueryImpl();
historicTaskInstanceQuery.processInstanceId(historicProcessInstanceEntity.getId()).orderByExecutionId().desc();
List<HistoricTaskInstance> historicTaskInstances = commandContext.getHistoricTaskInstanceEntityManager()
.findHistoricTaskInstancesByQueryCriteria(historicTaskInstanceQuery);
int index = 0;
for (HistoricTaskInstance historicTaskInstance : historicTaskInstances) {
if (historicTaskInstance.getId().equals(currentUserTaskEntity.getId())) {
break;
}
index++;
}
if (index > 0) {
HistoricTaskInstance previousTask = historicTaskInstances.get(index - 1);
TaskEntity newTaskEntity = createTaskFromHistoricTask(previousTask, commandContext);
currentExecution.addTask(newTaskEntity);
commandContext.getTaskEntityManager().insert(newTaskEntity);
AtomicOperation.TRANSITION_CREATE_SCOPE.execute(currentExecution);
} else {
// TODO: find the last task of the previous process instance
}
// To overcome the "Task cannot be deleted because is part of a running
// process"
TaskEntity currentUserTask = commandContext.getTaskEntityManager().findTaskById(fromTaskId);
if (currentUserTask != null) {
currentUserTask.setExecutionId(null);
commandContext.getTaskEntityManager().deleteTask(currentUserTask, "jumped to another task", true);
}
return null;
}
private TaskEntity createTaskFromHistoricTask(HistoricTaskInstance historicTaskInstance,
CommandContext commandContext) {
TaskEntity newTaskEntity = new TaskEntity();
newTaskEntity.setProcessDefinitionId(historicTaskInstance.getProcessDefinitionId());
newTaskEntity.setName(historicTaskInstance.getName());
newTaskEntity.setTaskDefinitionKey(historicTaskInstance.getTaskDefinitionKey());
newTaskEntity.setProcessInstanceId(historicTaskInstance.getExecutionId());
newTaskEntity.setExecutionId(historicTaskInstance.getExecutionId());
return newTaskEntity;
}
}
But the problem is I can see my task is created, but the execution does not point to it but to the current one.
I had the idea to use the activity (via the object ActivityImpl) to set it to the execution but I don't know how to retrieve the activity of my new task.
Can someone help me, please?

Answer 1

Unless somethign has changed in the engine significantly the code in the link you reference should still work (I have used it on a number of projects).
That said, when scanning your code I don't see the most important command.
Once you have the current execution, you can move the token by setting the current activity.
Like I said, the code in the referenced article used to work and still should.
Greg

Answer 2

Referring the same link in your question, i would personally recommend to work with the design of you your process. use an exclusive gateway to decide whether the process should end or should be returned to the previous task. if the generation of task is dynamic, you can point to the same task and delete local variable. Activiti has constructs to save your time from implementing the same :).