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What's the best way to design a process which allows user to recall back to his task.

chenning007

Hi folks,

I am not sure this is the proper place to raise this question, if not please kindly let me know.

My question: is it possible for activiti engine to allow user to recall back to his task, for example

start -> task A -> task B -> task C -> end

if task A is completed by user A, process goes to task B and waits for user B's completeness, however, before user B performs to complete task B, user A would like to recall the task from task B back to A and complete the task A again with more information. Is there any good way to design the process and achieve the requirement, please advice, thank you.

Best Regards!

– Ning

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chenning007

any comments please, I am waiting online

trademak

Hi,

You could use a signal boundary event on every task for example, that moves back to the previous task. You can then signal the process instance when necessary.

Best regards,

chenning007

Tijs,

Thanks for your reply…

Your proposal sounds a good idea to me, now we meet another trouble – we would allow to recall a task to any tasks which previously had been completed, for example, users who completed task A, B, C, D would require to recall current task E back to one of their tasks which would be task A, B, C or D.

Our current solution is to draw flow lines from task E to task A, B, C, D, but it results in a very big process(many flow lines) which is hard to be maintained. Based on your proposal, can we send the jump-back task name within the signal, when the signal is replied by boundary event, an new implemented service task which can parse target task from the received signal and jump the process back to target task directly. What's your idea on this solution, if you have anything better, please also advise, thank you.

–Ning

martin_grofcik

Hi Ning,

Another possibility could be to do not cover return back in process definition, but support it in admin functionality. (Command to take execution end return it to the state where you want to. (It is easy to do in activiti).

Regards
Martin

chenning007

Hi Martin,

I suppose the command you mentioned here is the internal implementation of xxxService classes(activiti API). Can these commands class be accessed by application directly, or I should implement my own customized API based on these command classes for this specific requirement?

Thanks!

–Ning

jbarrez

You can write custom Commands and pass these in the ManagementService.

tloomba

Hi Mr. Joram,

would you have an example of how to write a custom Command and use it for the above use case? I work in a company where the use case is similar. We have very large process models and our customer has the need to send the existing process instance upstream to a previous step, or downstream to a step that has not executed yet. Drawing transitions in the model will clutter them and not be scalable, especially when new models are created. If you could provide us with an example of using a custom Command, that would help as we have searched the forum and the web and did not find examples of creating custom Command.

Also, one of the customer's use case is to complete a process instance gracefully, as if it had ended as normal. If the instance is a sub-process created from a call activity of a parent process, the parent call activity should complete and instance should move to next step. We found the following example code from this forum, but it is throwing a null pointer exception at the "exec.end()" call. Would you be able to provide some information on why Activiti is throwing an NPE at this call? I would assume of ActivityExecution provides an end method, it should work.

This is the code we tested:

List<Execution> executions = runtimeService.createExecutionQuery().processDefinitionName("TestSendTo").list();
ActivityExecution exec = (ActivityExecution) executions.get(0);
exec.end();

Below is the exception:

org.activiti.rest.exception.ExceptionHandlerAdvice - Unhandled exception
java.lang.NullPointerException
at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:633)
at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:628)
at org.activiti.engine.impl.persistence.entity.ExecutionEntity.end(ExecutionEntity.java:398)
at com.thomsonreuters.workflowservice.service.SendToServiceImpl.completeInstances(SendToServiceImpl.java:105)

Any information you provide would be helpful. Thank you in advance of your time!

Tavishi Loomba

martin_grofcik

Hi,

would you have an example of how to write a custom Command and use it for the above use case?

An example of the new command usage:

<br>&nbsp;&nbsp;&nbsp; public void setExecutionToActivity(String executionId, String activityId) {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ProcessEngineConfigurationImpl processEngineConfiguration = &hellip;..<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; processEngineConfiguration.getCommandExecutor().execute(new SetActivityCmd(executionId, activityId));<br>&nbsp;&nbsp;&nbsp; }<br>&hellip;.<br>&nbsp;&nbsp;&nbsp; private static class SetActivityCmd implements Command<Void> {<br><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; private final String executionId;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; private final String activityId;<br><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; private SetActivityCmd(String executionId, String activityId) {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; this.executionId = executionId;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; this.activityId = activityId;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<br><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; @Override<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; public Void execute(CommandContext commandContext) {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ExecutionEntity execution = commandContext.getExecutionEntityManager().findExecutionById(this.executionId);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; execution.setActivity(new ActivityImpl(this.activityId, execution.getProcessDefinition()));<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return null;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<br><br>&nbsp;&nbsp;&nbsp; }<br>

Regarding deleting process instances:

<br>/**<br>&nbsp;&nbsp; * Delete an existing runtime process instance.<br>&nbsp;&nbsp; * <br>&nbsp;&nbsp; * @param processInstanceId<br>&nbsp;&nbsp; *&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; id of process instance to delete, cannot be null.<br>&nbsp;&nbsp; * @param deleteReason<br>&nbsp;&nbsp; *&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; reason for deleting, can be null.<br>&nbsp;&nbsp; * @throws ActivitiObjectNotFoundException<br>&nbsp;&nbsp; *&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; when no process instance is found with the given id.<br>&nbsp;&nbsp; */<br>&nbsp; void deleteProcessInstance(String processInstanceId, String deleteReason);<br>

NPE stack trace does not make sense without activiti version (It is not Activiti6 master branch 🙂 ) Can you create simple jUnit test?
https://forums.activiti.org/content/sticky-how-write-unit-test

Regards
Martin

tloomba

Hi Martin,

thank you very much for providing an example of creating and implementing a custom command. This worked well to the extent that the custom command does get executed without any errors. I tried the example you provided above, which is set the activity id of the current execution to the desired activity where we'd like to re-route the execution too. The execution however just sits at that activity without moving downstream. Is there a new job that needs to be created after setting the activity id? My main goal is to set the new activity id but also have the execution route to that activity and move downstream from there. Would you please tell us know how to do that?

Thank you very much for your help!

Tavishi Loomba

martin_grofcik

Hi Tavish,

The execution however just sits at that activity without moving downstream.

In the case when you wan to run the execution, you have to signal it.
e.g.:

<br>getCommandExecutor().execute(new SignalCmd(executionId, signalName, null,<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; null));<br>

Regards
Martin

tloomba

Hi Martin,

thank you again! What should be the value of the signalName parameter in the constructor call for SignalCmd? We tried null as signalName and also "compensationDone" which we found in various forum posts, but neither worked.

Also, will sending the Signal to the execution be enough to run the execution further, or are there additional commands we should invoke? I regret having to keep coming back to you for additional questions. There is no javadoc on classes such as SignalCmd, Command classes. We have spent lot of time searching Activiti forums and the web, but are not finding any concrete examples or documentation. Does documentation exist for how such design patterns (for example custom Command) should be implemented?

We are using Activiti version 5.19.

Thanks!
Tavishi

martin_grofcik

Hi Tavishi,

The best would be to create jUnit test as an example. When I will have a time I can create one. (Or you can help me too -> just prepare what you have to the jUnit test template https://forums.activiti.org/content/sticky-how-write-unit-test and I can add what is missing.)

Regards
Martin

tloomba

Thank you! Yes, I will prepare one and have it available by tomorrow. Does it matter that our project uses Sping Data JPA version 1.8 and Hibernate JPA version 2.0 with Activiti version 5.19? Can my unit test only include the H2 db configuration, or will it make a difference to the design implementation?

Also, how do I submit the unit test to you?

jbarrez

As long as we can run it easily, that's the main goal. H2 is preferred, yes.

> Also, how do I submit the unit test to you?

Github repo is the easiest

evavilaginés

Hi,
I'm very interested in this post because just I have to implement the "reverse" in a flow of activiti (to allow user to recall back to his task and forward).

Is there any available example of the solution described here? Or another better solution?

I have tried to implement the solution described here but not get it to work (I'm new programming in activiti) .

Any help is welcome.

Thank you very much,

martin_grofcik

Hi,

you can wait on Tavishi's jUnit test our you can create your own, and we can work on the example together.
https://forums.activiti.org/content/sticky-how-write-unit-test

Regards
Martin

tloomba

Martin and Joram,

Thank you very much for your responses. I will creating and posting the Junit test in a couple of weeks. I really appreciate your input and help.

Thanks!
Tavishi

tloomba

Hi Martin,

I created the unit test in the maven project template your team provides. Please download "SendToActivitiUnitTest.zip" from https://github.com/tloomba/SendToTestTavishi. As a recap, following is the use case I am trying to achieve:

Re-route a process instance from a downstream step where it is stopped at a wait state to a previous upstream step, and have the execution move downstream based on the transition conditions, as it normally would the first time it entered the upstream step. In the attached project I created a sample process called TestSendTo.bpmn. In this process the first wait state the execution could stop at is User Task 1. When the execution moves downstream it could stop at User Task 2, and further downstream it will always stop at Receive Task. Following are the types of re-routing use cases I would like to achieve:

1) When the process has moved downstream and stopped at Receive Task, re-route it to Service Task 1. The execution should move downstream from Service Task 1 as it normally would, based on the transition conditions.

2) If the process has moved downstream and stopped at User Task 2, re-route it to Service Task 1. The execution should move downstream from Service Task 1 as it normally would, based on the transition conditions.

3) If the process has moved downstream and stopped at User Task 2, re-route to User Task 1. The execution should move downstream from User Task 1 once it is completed, as it normally would, based on the transition conditions.

Just to clarify again, our goal is to achieve above use cases without drawing transitions in the process model. I added a unit test in MyUnitTest.java which attempts use case #1. As you see I created a custom command with the code you provided above on May 31st. I invoked the custom command to achieve the re-routing from Receive Task to Service Task 1, and then signaled the command as you suggested above using the line:

"commandExecutor.execute(new SignalCmd(task.getExecutionId(), "compensationDone", null, null))"

The process instance should now have moved to User Task 1 since the variable 'goToUserTask' was set to true. However, if you execute the unit test you will notice at line 68 when we retrieve the process instance again, it seems to have stopped at Service Task 1 and does not move downstream. We did not know what should be the value of the "signalName" parameter for SignalCmd constructor. Our project is depending on the satisfaction of these use cases for the success of the project, and we also are nearing our deadline in a few weeks. I'd have immense gratitude if you are able to review this and get back to me at your earliest convenience!

Thanks,
Tavishi

tloomba

Hello Martin, Activiti team,

could I please request you to review the above unit test I posted and my questions as soon as you are available? We are on a crunched time-line for our project to develop this use case and your input is very critical for us. I regret any inconvenience caused.

Thanks!
Tavishi

martin_grofcik

Hi Tavishi.

Cases 1 - 3 (and more) are implemented in the project
https://github.com/martin-grofcik/activiti-unit-test-grasshopper

I simplified a task with adding receivetask0 activity into process diagram. (because we had no wait state which can accept signal there. The simplification can be replaced by new FlowNodeActivityBehavior which will accept signals on the service tasks and start tasks too.

Regards
Martin

tloomba

Hi Martin,

thank you so much for writing these unit tests and they look great! I only have one issue: All of our models are already developed and are being released to our customers soon. All of the code base that starts process instances is also already developed and is in various places within a large code base. Most of our models have a service task as one of the first activities. Therefore, if we need to edit each model to add a receive task as the first activity, it will need a lot of work. Also, every place where a process instance is started, we will need to update the code so the process instance doesn't get stuck at the receive task. This will be a lot of work.

So, would you be able to please give me an example of the FlowNodeActivityBehavior which you mentioned, that can accept signals on the service tasks and start tasks too?

Thanks!
Tavishi

ygu

Hi,

It seems I have quite the same requirement as tloomba. Thanks a lot Martin for the code you posted on github.

I have a question though: I used the same code in my application, and it seems that the RestartInstanceActivitiCommand(String executionId, String activityId) sets the cursor to the end of the indicated activity in the indicated execution. Is this the intended behavior of this code ? Would it be possible to set the cursor to the start of the activity instead ?

Regards,

ygu

ajeje93

Hi,

I'm trying to use your code to skip a task in a process. For example, I have a process start-->userTask1-->userTask2-->userTask3-->end, so I'm checking if I completed userTask1 and after I'm using the command executor as you described above to jump to userTask3, skipping userTask2.

The thing is that whenever I execute the command I get the following error:

[main] ERROR org.activiti.engine.impl.interceptor.CommandContext - Error while closing command context
java.lang.NullPointerException
   at org.activiti.engine.impl.persistence.entity.ExecutionEntity.signal(ExecutionEntity.java:414)
   at org.activiti.engine.impl.persistence.entity.TaskEntity.complete(TaskEntity.java:203)
   at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:52)
   at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:24)
   at org.activiti.engine.impl.cmd.NeedsActiveTaskCmd.execute(NeedsActiveTaskCmd.java:59)
   at org.activiti.engine.impl.interceptor.CommandInvoker.execute(CommandInvoker.java:24)
   at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:57)
   at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:31)
   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:178)
   at com.example.OnboardingRequest.main(OnboardingRequest.java:59)

I also downloaded the unit test on your github, but when I'm trying to transpose your code into mine, I get the same error.

Have you some ideas why is this happening? Probably I'm making some silly mistake because I'm a beginner with Activiti.

Thank you in advance.

shubham_kankari

Hey, did you figure out how to do this using FlowNodeActivityBehavior?

nirmalsandip

Thanks martin for nice, easy to understand code.

I am trying to do same thing(Restarting a process from specified step in flow).

I have converted above code for Activiti 6?

public class RestartInstanceActivitiCommand implements Command<Void> {

private final String executionId;
private final FlowElement flowElement;

public RestartInstanceActivitiCommand(String executionId, FlowElement flowElement) {
this.executionId = executionId;
this.flowElement = flowElement;
}

public Void execute(CommandContext commandContext) {
ExecutionEntity execution = commandContext.getExecutionEntityManager().findById(this.executionId);
execution.setCurrentFlowElement(flowElement);
return null;
}
}

Triggered it with :

ProcessEngineConfigurationImpl processEngineConfiguration = (ProcessEngineConfigurationImpl) processEngine
.getProcessEngineConfiguration();

CommandExecutor commandExecutor = processEngineConfiguration.getCommandExecutor();

BpmnModel bpmnModel = repositoryService.getBpmnModel("activitiPoc:2:5004");
FlowElement flowElement = bpmnModel.getFlowElement("filterData");
commandExecutor.execute(new RestartInstanceActivitiCommand(processInstanceId, flowElement));
runtimeService.trigger(processInstanceId);

The process is going to the desired state, but it is getting stuck at that step itself.

Tried to restart the process with :

servce task : The process execution moves to service task, but It's not getting called automatically as it would normally.

User Task : The process instance is not getting assigned to the mentioned user mentioned in the userTask. Just cursor moves to user task.

Also I did not find any code sample forFlowNodeActivityBehavior.

Really appreciate help on this!