Time for action – using Esper with Activiti

We will use Esper in Activiti by performing the following steps:

  1. We will create a new Activiti project in Eclipse named EsperinActiviti, and within this project, we will model an Activiti diagram named leaverequest_withespertest.bpm. We will model the diagram as in the following screenshot and assign the user task to fozzie:
    Time for action – using Esper with Activiti
  2. Now we will create two execution listener classes, ProcessStartExecutionListener and ProcessEndExecutionListener.
  3. The ProcessStartExecutionListener class will consist of the following lines of code:
    public class ProcessStartExecutionListener implements ExecutionListener {

  @Override
  public void notify(DelegateExecution execution) throws Exception {
    LeaveRequestReceivedEvent event = new LeaveRequestReceivedEvent(
        execution.getId(), 
        new Date().getTime(), 
        (Integer) execution.getVariable("leaveDay"));
        EPServiceProviderManager.getDefaultProvider().getEPRuntime()
        .getEventSender("LeaveRequestReceivedEvent")
        .sendEvent(event);
  }
}
  4. The ProcessEndExecutionListener class will consist of the following lines of code:
    public class ProcessEndExecutionListener implements ExecutionListener {

  @Override
  public void notify(DelegateExecution execution) throws Exception {
    LeaveRequestProcessedEvent event = new LeaveRequestProcessedEvent (
      execution.getId(), 
      new Date().getTime(),
      (Boolean) execution.getVariable("requestApproved"),
      (Integer) execution.getVariable("leaveDay"));
    EPServiceProviderManager.getDefaultProvider().getEPRuntime()
      .getEventSender("LeaveRequestProcessedEvent")
      .sendEvent(event);
  }
}
  5. Now we will assign these listeners on the start and end events of the process, as displayed in the following screenshot:
    Time for action – using Esper with Activiti
  6. We will create a class file named LeaveRequestProcessedEvent with the following code. This class file checks the time taken by the process to complete.
    public class LeaveRequestProcessedEvent {
  
  // For correlating the events.
  @XmlElement
  private final String processInstanceId;
  @XmlElement
  private final long processedTime;
  @XmlElement
  private final boolean requestApproved;
  @XmlElement
  private final int requestedDay;
  
  @SuppressWarnings("unused")
  private LeaveRequestProcessedEvent() {
    processInstanceId = null;
    processedTime = 0;
    requestApproved = false;
    requestedDay = 0;
  }

  public LeaveRequestProcessedEvent(String processInstanceId, long processedTime, boolean requestApproved, int requestedDay) {
    this.processInstanceId = processInstanceId;
    this.processedTime = processedTime;
    this.requestApproved = requestApproved;
    this.requestedDay = requestedDay;
  }

LeaveRequestProcessedEvent method used to take process instance, processed time and request approve.
 
  public String getProcessInstanceId() {
    return processInstanceId;
  }

  public long getProcessedTime() {
    return processedTime;
  }

  public boolean isRequestApproved() {
    return requestApproved;
  }
  
  public int getRequestedDay() {
    return requestedDay;
  }

  @Override
  public String toString() {
    return "LeaveRequestProcessedEvent{processInstanceId="+processInstanceId+",processedTime="+processedTime+",requestApproved="+requestApproved+",requestedDay="+requestedDay+"}";
  }
}
  7. Create a LeaveRequestReceivedEvent class with the following code. This class file will check the time taken to receive the request for the process.
    public class LeaveRequestReceivedEvent {

  // For correlating the events.
  @XmlElement
  private final String processInstanceId;
  @XmlElement
  private final long receiveTime;
  @XmlElement
  private final int requestedDay;
  
  @SuppressWarnings("unused")
  private LeaveRequestReceivedEvent() {
    processInstanceId = null;
    receiveTime = 0L;
    requestedDay = 0;
  }
  
  public LeaveRequestReceivedEvent(String processInstanceId, long receiveTime, int requestedDay) {
    this.processInstanceId = processInstanceId;
    this.receiveTime = receiveTime;
    this.requestedDay = requestedDay;
  }

  public String getProcessInstanceId() {
    return processInstanceId;
  }

  public long getReceiveTime() {
    return receiveTime;
  }

  public int getRequestedDay() {
    return requestedDay;
  }

  @Override
  public String toString() {
    return "LeaveRequestReceivedEvent{processInstanceId="+processInstanceId+",receiveTime="+receiveTime+",requestedDay="+requestedDay+"}";
  }
}
  8. Now we will create a test class, TimeactivitiTest, for unit testing. We will split this class for better understanding. We create the TimeactivitiTest class as follows:
    public class TimeactivitiTest {

}
  9. Place the following code in the test class to configure the Esper engine in Activiti:
      private EPRuntime epRuntime;
  private EPAdministrator epAdmin;

  @Before
  public void startEsper() {
    Configuration configuration = new Configuration();
    configuration.addEventTypeAutoName("org.activiti.event");
    EPServiceProvider epService = EPServiceProviderManager.getDefaultProvider(configuration);
    epRuntime = epService.getEPRuntime();
    epAdmin = epService.getEPAdministrator();
  }
  10. Now we will create some variables to fetch the average and maximum process time of the process, as shown in the following code:
    private Queue<Double> avgProcessDurationQueue = new LinkedList<Double>();
  private Queue<Long> maxProcessDurationQueue = new LinkedList<Long>();
  11. Create a test method to perform the testing of the process execution, as shown in the following code:
    @Test
  public void monitorProcessDuration() {
    epRuntime.sendEvent(new TimerControlEvent(ClockType.CLOCK_EXTERNAL));

    EPStatement epStatement = epAdmin.createEPL(new StringBuffer()
        .append("select avg(endEvent.processedTime - beginEvent.receiveTime) as avgProcessDuration, ")
        .append("max(endEvent.processedTime - beginEvent.receiveTime) as maxProcessDuration ")
        .append("from pattern [every beginEvent=LeaveRequestReceivedEvent -> endEvent=LeaveRequestProcessedEvent(processInstanceId=beginEvent.processInstanceId)].win:time(5 sec)")
        .toString());
    
    epStatement.addListener(new UpdateListener () {
      public void update(EventBean[] newEvents, EventBean[] oldEvents) {
        Assert.assertEquals(1, newEvents.length);
        Assert.assertNull(oldEvents);
        Double avgProcessDuration = (Double) newEvents[0].get("avgProcessDuration");
        Long maxProcessDuration = (Long) newEvents[0].get("maxProcessDuration");
        System.out.println
("avgProcessDuration="+avgProcessDuration+", maxProcessDuration="+maxProcessDuration);
        avgProcessDurationQueue.add(avgProcessDuration);
        maxProcessDurationQueue.add(maxProcessDuration);
      }
    } );
    
    sendLeaveRequestReceivedEvent (   0, "1", 100);
    assertMonitoredProcessDuration(null, null);
    
    sendLeaveRequestReceivedEvent ( 300, "2", 200);
    assertMonitoredProcessDuration(null, null);
    
    epStatement.destroy();
  }
  12. Add the following methods as we are using them in our test case:
    private void assertMonitoredProcessDuration(Double avgProcessDuration, Long maxProcessDuration) {
    Assert.assertEquals(avgProcessDuration, avgProcessDurationQueue.poll());
    Assert.assertEquals(maxProcessDuration, maxProcessDurationQueue.poll());
  }

  private void sendLeaveRequestReceivedEvent(long time, String processInstanceId, int requestedAmount) {
    sendEvent(time, new LeaveRequestReceivedEvent(processInstanceId, time, requestedAmount));
  }

  private void sendLeaveRequestProcessedEvent(long time, String processInstanceId, boolean requestApproved, int LeaveedAmount) {
    sendEvent(time, new LeaveRequestProcessedEvent(processInstanceId, time, requestApproved, LeaveedAmount));
  }

  private void sendEvent(long time, Object event) {
    System.out.printf(" %1$4d : %2$s
", time, event);
    epRuntime.sendEvent(new CurrentTimeEvent(time));
    epRuntime.sendEvent(event);
  }

What just happened?

We went through how to use Esper in Activiti for monitoring our business process. We have also monitored a process by executing an Esper query.

Have a go hero

Having gone through the chapter, feel free to attempt the following. You can refer to the examples implemented earlier.

  • Implement a Sub-Process, either embedded or standalone, to issue a driving license based on the applicant's age, and use the same Sub-Process for the vehicle registration process
  • Design a process and use task listeners to complete the user task

Pop quiz – the Activiti Process Engine

Q1. Which Sub-process can be used in any main process?

  1. Embedded Sub-Process
  2. Multi-instance Sub-Process
  3. Standalone Sub-Process
  4. None

Q2. Which tab is used to implement a multi-instance task?

  1. Listener
  2. Multi-instance
  3. Form
  4. None

Q3. Which gateway doesn't require conditions?

  1. Exclusive
  2. Inclusive
  3. Parallel
  4. None
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