Working with Signal Events

The following scenario simulates a simple leave approval business process, in which an employee fills a form and submits the leave request to the manager and the manager approves or rejects it. The employee receives an email if the manager approves the request. Otherwise, if the manager rejects it, the employee will be able to resend the leave request by adjusting it. 

You can use Signal Events to perform an additional external task depending on the status of a business process. Thus, S ignal Events pass information about an event in a BPMN process.  For example, in this scenario if the manager has to update a leave management system whenever he/she approves a leave request of an employee. You can use a Signal Event to pass information about the leave approval before sending the confirmation email to the employee.

Let's get started! This tutorial includes the following sections:

Importing artifacts 

If you did not try the Working with Timer Boundary Events tutorial yet, follow the steps below to import its artifacts as you will be extending on that.

1. Download the pre-packaged project and extract it to a preferred location. This contains the artifacts of the Working with Timer Boundary Events tutorial. 

2. Open the WSO2 EI Tooling environment.

3. Click File, and click Import. 

4. Expand the WSO2 category, select Existing WSO2 Projects into workspace and click Next.

5. Click Browse, select the file you extracted and upload it.  

6. In the Package Explorer, double click on the name of the BPMN diagram to view the BPMN artifacts you imported.

Creating new artifacts

The next step of the process is adding the Signal Event for the manager to update a leave management system when the manager approves a leave request. Follow the steps below to implement this.

1. Click on the canvas,click Signals in the Properties tab and click New,  to add a new signal definition.
   

2. Enter the following values to add attributes to the signals.

   • ID - leaveSignal

   • Name - Leave Signal

   • Scope - global

     Open

     

3. Drag and drop a Signal Throwing Event to the canvas from the Intermediate event tab of the Palette.
   
   

4. Click on the Signal Throwing Event  and  select Leave Signal (leaveSignal) as the Signal ref  in the  Main config  section of the  Properties  tab.
   

5. Hover your mouse pointer over the Exclusive Gateway , and click on the arrow icon (i.e., the  Create Connection  option) and connect it to the  Signal Throwing Event .
   

6. Click on the arrow, which connects the  Exclusive Gateway  to the Signal Throwing Event  and enter  ${vacationApproved == 'true'}  as the value for  Condition  in the  Main config   section of the  Properties  tab.
   

7. Hover your mouse pointer over the Signal Throwing Event , and click on the arrow icon (i.e., the  Create Connection  option) and connect it to the Send confirmation email Mail Task .
   

   
   
   Now, a signal will be thrown whenever the manager approves a leave request.
   

8. Drag and drop a Signal Start Event to the canvas from the Start event tab of the Palette.
   
   

   
   

9. Click on the  Signal Start Event  and  select Leave Signal (leaveSignal) as the  Signal ref  in the  Main config  section of the  Properties  tab.
   

   
   

10. Drag and drop a  User Task  to the diagram from the Task tab of the Pallet .
    

11. Click on the User Task and  enter  Update records  as the  Name  in the  General  section of the Properties tab.
    
    

    
    

12. Hover your mouse pointer over the Signal Start Event , and click on the arrow icon (i.e., the  Create Connection  option) and connect it  to the Update records  User Task .
    

13. Right click on the arrow, which connects the Exclusive Gateway to the Send confirmation email Mail Task and click Delete.
    

14. Click on the Update records User Task, click New in the  Form  section of the  Properties  tab and add the following fields.  

    You view the fields you added as shown below.

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15. Click on the Update records   User Task and enter manager as the Assignee in the Main config section of the Properties tab.
    

    
    

16. Drag and drop a  End Event  to the diagram from the End event tab of the  Pallet .

17. Hover your mouse pointer over the Update records  User Task , and click on the arrow icon (i.e., the  Create Connection  option) and connect it  to the  End Event .
    
    

    
    

18. Press  Ctrl+S  to save all the artifacts, which you created in WSO2 EI Tooling.
    The model is now complete as the necessary logic has been applied.