You work for a demanding, yet friendly credit card company.

And you’ve almost finished building their business process in jBPM.

Your promotion is so close you can taste it..

But when you scroll through the list of service tasks, you can’t find one to save the process information to your database.

Are you doomed? No. You can create a work item handler to..

Connect with External Services

If you want your process to connect to external systems (databases, web services) or execute special business logic, then you can..

Create a Custom Work Item Handler

We’ll create a custom work item handler in JBoss Dev Studio. But you can also do this in Business Central.

What You’ll Need

  1. JBoss Developer Studio w/ JBoss EAP 6.4
  2. Basic Maven & BPM knowledge
  3. JBPM Eclipse modeler. Download here

Create a Custom Service Task

  1. Download the simple-process-workitemhandler project
    • This project contains a bpm process that prints “Hello World”
    • We’ll change this script task to a custom task that executes our logic
    • Import this project in JBoss Developer Studio
  2.  Define a Work Item
    • Create a file src/main/resources/META-INF/MyWorkDefinitions.wid

      import org.drools.core.process.core.datatype.impl.type.StringDataType;
      
      [
       [
       "name" : "Random Number",
       "parameters" : [
       "Message" : new StringDataType(),
       ],
       "displayName" : "Random Number",
       "icon" : "icon-info.gif"
       ]
      ]
    • Here we define the name of our task, a parameter and an icon
  3. Cleanup our process
    • Right click com/sample/sample.bpm → Open with → BPMN Diagram Editor

    • Delete the script task and end node.
  4. Create a Custom Service Task
    • Create a Random Number Task
    • To add a parameter, double click the Random Number task

    • Click the pencil next to Message

    • Select ‘Expression’ and type your name. Click Ok
    • Save the process
  5. Add a Terminate Node
  6. Connect the Service Task and Work Item Handler
    • Create a file /src/main/resources/META-INF/kie-deployment-descriptor.xml

      <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
      <deployment-descriptor xsi:schemaLocation="http://www.jboss.org/jbpm deployment-descriptor.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
       <work-item-handlers>
       <work-item-handler>
       <resolver>mvel</resolver>
       <identifier>new org.codelikethewind.workitemhandler.RandomWorkItemHandler()</identifier>
       <parameters/>
       <name>Random Number</name>
       </work-item-handler>
       </work-item-handlers>
      </deployment-descriptor>
    • This registers our service task to the work item handler that we’ll create next.
  7. Build the project
    • Right click your project (simple-process) -> Run as -> Maven Build.
      Goals: clean install

Create a WorkItemHandler

  1. Download the embedded-process-workitemhandler project
    • This web app runs the bpm process we just worked on. When we’re done, that process will execute a custom work item handler
  2. Create a Custom Work Item Handler
    • In package org.codelikethewind.workitemhandler, create a class called RandomWorkItemHandler

      public class RandomWorkItemHandler implements WorkItemHandler {
      }
    • Implement the execute and abort methods

      @Override
      public void abortWorkItem(WorkItem workItem, WorkItemManager manager) {
          manager.abortWorkItem(workItem.getId());
      }
      
      @Override
      public void executeWorkItem(WorkItem workItem, WorkItemManager manager) {
      
          Random rand = new Random();
          int  n = rand.nextInt(50) + 1;
          
          Object name = workItem.getParameter("Message");
          System.out.println("Hi " + name + ", your random number is: " + n);
      
          manager.completeWorkItem(workItem.getId(), null);
      }
  3. Build the project
    • Right click your project (embedded-process-workitemhandler) -> Run as -> Maven Build.
      Goals: clean install

Run the Process

  1. Deploy the simple-embedded-process 
    • Steps 1 & 2 of Method 1 here
  2. Start the process
  3. Check your server logs
    • If your process prints out a random number, you’ve successfully built a custom work item handler!

Recap

Create a Custom Service Task

  • We defined the structure of our work item — a custom task in your process. It has a name, one parameter, and an icon. [PIC]
  • We added the custom task to our process and filled in a parameter
  • We created a deployment descriptor to connect this service task to the work item handler.

Create a WorkItemHandler

  • We created a custom work item handler to print a random number
  • Our Work Item Handler is simple, but you can implement any complex logic.

Run the Process

  • Once the process hits our service task, the execute() method in RandomWorkItemHandler will run

For Business Logic, Not Data

Use work item handlers (the java class) to run business logic, not create data. Your data should be passed in as a parameter to your custom work item (the service task).

This makes your process easy to update, test, and maintain.

So..

  1. Custom Work Item Handlers help us connect to external services or execute business logic
  2. We define a work item (service task), a work item handler (the implementation), and run it in our process
  3. Use work item handlers for logic, not data!

Source Code & Useful Links

  1. Finished projects: simple-process-workitemhandler & embedded-process-workitemhandler
  2. Official jBPM Documentation of Custom Service Tasks
  3. Creating Work Item Handlers in Business Central

Happy Coding!

-T.O.

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