Integration of a subprocess definition in JBPM JPDL

Question

Hi,

I'm using the process definition language jPDL from the JBoss Workflow engine : jBPM.

I want to integrate a very simple process definition graph : Basically, I have a main process definition (simple/processdefinition.xml) including :

• a Start node,
• a Process State node,
• an End node.

Here is the definition of the graph :

<process-definition 
  xmlns="urn:jbpm.org:jpdl-3.2"
  name="simple">
   <start-state name="start">
        <transition name="to_state" to="process-state">
         <action name="action" class="com.sample.action.MessageActionHandler">
            <message>
                    Going to the sub-state!
                </message>
         </action>
      </transition>
        <event type="node-leave">
            <action class="com.sample.action.MessageActionHandler">
                <message>
                    Start.
                </message>
            </action>
        </event>
   </start-state>
   <process-state name="process-state">
        <sub-process name="subsimple" binding="late"/>
        <variable access="read,write" name="message" mapped-name="message">        </variable>
        <event type="node-enter">
            <action class="com.sample.action.MessageActionHandler"></action>
        </event>
        <transition to="end" name="to_end"></transition>
    </process-state>
   <end-state name="end">
        <event type="node-enter">
            <action class="com.sample.action.MessageActionHandler">
                <message>
                    End.
                </message>
            </action>
        </event>
    </end-state>
</process-definition>

Within the Process State node I defined a Sub-Process graph (subsimple/processdefinition.xml) containing :

• a Start node,
• a State node,
• an End node.

Here is the definition of the graph :

<process-definition 
  xmlns="urn:jbpm.org:jpdl-3.2"
  name="subsimple">
   <start-state name="start">
        <transition name="to_state" to="first">
         <action name="action" class="com.sample.action.MessageActionHandler">
            <message>Going to the first state!</message>
         </action>
      </transition>
        <event type="node-leave">
            <action class="com.sample.action.MessageActionHandler">
                <message>
                    Start.
                </message>
            </action>
        </event>
   </start-state>
   <state name="first">
      <event type="node-enter">
            <action class="com.sample.action.MessageActionHandler">
                <message>
                    In first state !!
                </message>
            </action>
        </event>
        <transition name="to_end" to="end">
         <action name="action" class="com.sample.action.MessageActionHandler">
            <message>
                    About to go out of sub-process !
                </message>
         </action>
      </transition>
   </state>
   <end-state name="end">
        <event type="node-enter">
            <action class="com.sample.action.MessageActionHandler">
                <message>
                    End.
                </message>
            </action>
        </event>
    </end-state>
</process-definition>

Here is the ActionHandler allocated to every events and transitions :

public class MessageActionHandler implements ActionHandler {

    private static final long serialVersionUID = 1L;

    String message;

    public void execute(ExecutionContext context) throws Exception {
        context.getContextInstance().setVariable("message", message);

        System.out.println(context.getContextInstance().getVariable("message"));
    }
}

Eventually, here is the Main class from which I start the whole process :

public class testJBPM {

public static void main(String[] args) {

    ProcessDefinition processDefinition = ProcessDefinition
            .parseXmlResource("simple/processdefinition.xml");

    // Create an instance of the process definition.
    ProcessInstance instance = new ProcessInstance(processDefinition);

    // Move the process instance from its start state to the first state.
    instance.signal();

    // Move the process instance to the end state.
    instance.signal();
}
}

As I read on JBoss forum, I correctly set binding=late on sub-process binding in main process definition. Then I tried different ways to instanciate the process definition of the sub-process but I always get the following Exception when trying to enter the sub-state/sub-process node :

Exception in thread "main" org.jbpm.JbpmException: can't create a process instance     when processDefinition is null
    at org.jbpm.graph.exe.ProcessInstance.<init>(ProcessInstance.java:128)
    at org.jbpm.graph.exe.ProcessInstance.<init>(ProcessInstance.java:92)
    at org.jbpm.graph.exe.Token.createSubProcessInstance(Token.java:624)
    at org.jbpm.graph.node.ProcessState.execute(ProcessState.java:164)
    at org.jbpm.graph.def.Node.enter(Node.java:319)
    at org.jbpm.graph.def.Transition.take(Transition.java:151)
    at org.jbpm.graph.def.Node.leave(Node.java:394)
    at org.jbpm.graph.node.StartState.leave(StartState.java:70)
    at org.jbpm.graph.exe.Token.signal(Token.java:195)
    at org.jbpm.graph.exe.Token.signal(Token.java:140)
    at org.jbpm.graph.exe.ProcessInstance.signal(ProcessInstance.java:271)
    at com.sample.main.testJBPM.main(testJBPM.java:21)

Can anybody give me advices on how to manage sub-process definition and use ?

Answer 1

I eventually found a way-out by myself :

• First, only one instance.signal(); is necessary to impulse the whole processes trail in main().

• Then, an interface has to be implemented to allow jBPM to search and instanciate the required sub-processes :

  public class DbSubProcessResolver implements SubProcessResolver {
      private static final long serialVersionUID = 1L;
  
  
      public ProcessDefinition findSubProcess(Element subProcessElement) {
  
  
          String name = subProcessElement.attributeValue("name").replaceAll(
              "\\.", "");
          ProcessDefinition subProcessDefinition = ProcessDefinition
              .parseXmlResource(name + "/processdefinition.xml");
  
  
          return subProcessDefinition;
      }
  
  
  }
  

• Eventually, a jBPM configuration file has to be specified to map the jBPM framework resolver to the implemented one :

  <jbpm-configuration>
      <bean name="jbpm.sub.process.resolver" class="com.sample.resolver.DbSubProcessResolver" />
  </jbpm-configuration>
  

... and it works fine !