Manually controlling execution of nodes

[michaelklem]

I created the following process definition

<process-definition xmlns="urn:jbpm.org:jpdl-3.1" name="test1">
 <start-state name="start">
 <transition name="step1" to="step1"/>
 </start-state>
 <end-state name="end"/>
 <state name="step1">
 <transition name="step2" to="step2"/>
 </state>
 <state name="step2">
 <transition name="step3" to="step3"/>
 </state>
 <state name="step3">
 <transition name="step4" to="step4"/>
 </state>
 <state name="step4">
 <transition name="step5" to="step5"/>
 </state>
 <state name="step5">
 <transition name="end" to="end"/>
 </state>
</process-definition>

I am trying to manually control which state gets executed next. For example, once the process is started, I am trying to execute the states in the following order:
step1
step1
step4
step3
step3
step2
step5

I am able to do so with the following code

 /**
 Sequence Control Test.
 Verify that we can specify which token to taken on a simple sequential process.
 TEST1_PROCESS is a sequential process definition of wait states.
 Once we start the process, we should be able to step to any node we want.
 */

 public void test1()
 {

 try {
 // Deploy the process definition
 init( TEST1_PROCESS );

 JbpmContext jbpmContext = sJbpmConfiguration.createJbpmContext();
 GraphSession graphSession = jbpmContext.getGraphSession();
 ProcessDefinition processDefinition = graphSession.findLatestProcessDefinition( "test1" );
 ProcessInstance processInstance = new ProcessInstance( processDefinition );

 long processDefId = processDefinition.getId();
 long processId = processInstance.getId();
 Token token = processInstance.getRootToken();
 assertTrue( processDefinition.getNode( "start" ).equals( token.getNode() ) );

 processInstance.signal();
 assertTrue( processDefinition.getNode( "step1" ).equals( token.getNode() ) );
 jbpmContext.close();

 Node n;

 // Go to step 1
 jbpmContext = sJbpmConfiguration.createJbpmContext();
 graphSession = jbpmContext.getGraphSession();
 processInstance = graphSession.loadProcessInstance( processId );
 processDefinition = graphSession.loadProcessDefinition( processDefId );
 n = processDefinition.getNode( "start" );
 token = processInstance.getRootToken();
 token.setNode( n );
 token.signal();
 assertTrue( processDefinition.getNode( "step1" ).equals( token.getNode() ) );
 jbpmContext.close();


 // Go to step 1
 jbpmContext = sJbpmConfiguration.createJbpmContext();
 graphSession = jbpmContext.getGraphSession();
 processInstance = graphSession.loadProcessInstance( processId );
 processDefinition = graphSession.loadProcessDefinition( processDefId );
 n = processDefinition.getNode( "start" );
 token = processInstance.getRootToken();
 token.setNode( n );
 token.signal();
 assertTrue( processDefinition.getNode( "step1" ).equals( token.getNode() ) );
 jbpmContext.close();


 // Go to step 4
 jbpmContext = sJbpmConfiguration.createJbpmContext();
 graphSession = jbpmContext.getGraphSession();
 processInstance = graphSession.loadProcessInstance( processId );
 processDefinition = graphSession.loadProcessDefinition( processDefId );
 n = processDefinition.getNode( "step3" );
 token = processInstance.getRootToken();
 token.setNode( n );
 token.signal();
 assertTrue( processDefinition.getNode( "step4" ).equals( token.getNode() ) );
 jbpmContext.close();


 // Go to step 3
 jbpmContext = sJbpmConfiguration.createJbpmContext();
 graphSession = jbpmContext.getGraphSession();
 processInstance = graphSession.loadProcessInstance( processId );
 processDefinition = graphSession.loadProcessDefinition( processDefId );
 n = processDefinition.getNode( "step2" );
 token = processInstance.getRootToken();
 token.setNode( n );
 token.signal();
 assertTrue( processDefinition.getNode( "step3" ).equals( token.getNode() ) );
 jbpmContext.close();


 // Go to step 3
 jbpmContext = sJbpmConfiguration.createJbpmContext();
 graphSession = jbpmContext.getGraphSession();
 processInstance = graphSession.loadProcessInstance( processId );
 processDefinition = graphSession.loadProcessDefinition( processDefId );
 n = processDefinition.getNode( "step2" );
 token = processInstance.getRootToken();
 token.setNode( n );
 token.signal();
 assertTrue( processDefinition.getNode( "step3" ).equals( token.getNode() ) );
 jbpmContext.close();


 // Go to step 2
 jbpmContext = sJbpmConfiguration.createJbpmContext();
 graphSession = jbpmContext.getGraphSession();
 processInstance = graphSession.loadProcessInstance( processId );
 processDefinition = graphSession.loadProcessDefinition( processDefId );
 n = processDefinition.getNode( "step1" );
 token = processInstance.getRootToken();
 token.setNode( n );
 token.signal();
 assertTrue( processDefinition.getNode( "step2" ).equals( token.getNode() ) );
 jbpmContext.close();


 // Go to step 5
 jbpmContext = sJbpmConfiguration.createJbpmContext();
 graphSession = jbpmContext.getGraphSession();
 processInstance = graphSession.loadProcessInstance( processId );
 processDefinition = graphSession.loadProcessDefinition( processDefId );
 n = processDefinition.getNode( "step4" );
 token = processInstance.getRootToken();
 token.setNode( n );
 token.signal();
 assertTrue( processDefinition.getNode( "step5" ).equals( token.getNode() ) );
 jbpmContext.close();
 }
 catch( Exception ex ) {
 ex.printStackTrace();
 fail();
 }

 } /* test1 */

This code works but it seems like there must be a better/easier way to do this in jBPM. I read all the docs and searched the forums but was unable to find an answer that was obvious to me. Am I missing something here or is this something I should not be doing with jBPM?

Thanks

[kukeltje]

Why does it seem that there must be an easier way to do this?

The P in BPM stands for process (= defined sequence of tasks/states/etc..) What you try to do creating ad-hoc processes.

Two possible 'solutions' come to mind however:

If the number of tasks is limited, you could try to make a web (meaning connect every node via a transition to another node).

If the number grows jou could try a hub-spoke model. Put a decision node in the middle, have a transition to each task and each task back to the decision. Then use a process variable (or something else) to decide which task to go to from the decision.

Just some ideas

[michaelklem]

Thanks for your quick response.

As a jBPM newbie I wasn't sure if I was actually doing this the correct way. I didn't want to hack it but looking through the source I saw no other way.

I have thought of the ideas you already posted and since they are similar I feel more confident that I am grasping jBPM.

Thanks again.

[kukeltje]

another quick response:

It is the first time I came across a question like this, so 'the correct way' is not the 'normal way' :-)

Your solution is as good as mine with the difference that both my solutions visually represent what can happen.
Your solution doesn't, but it is technically as good.