Activiti bpmn - missing variable comparision to false

Question

In my BPMN file I have an gateway defined as follows:

<exclusiveGateway id="gateway" name="An gateway"/>

<sequenceFlow id="sequence1" sourceRef="gateway"
        targetRef="task1">
    <conditionExpression xsi:type="tFormalExpression">${variableABC == true}
    </conditionExpression>
</sequenceFlow>

<sequenceFlow id="sequence2" sourceRef="gateway"
        targetRef="task2">
        <conditionExpression xsi:type="tFormalExpression">${variableABC == false}
    </conditionExpression>
</sequenceFlow>

I wonder what is going to happen when the variable variableABC is missing (not set in the workflow engine)?

From my tests it seems that the flow will go to second branch. Could anyone explain why?

In Java null == false would throw an exception (?). How does activiti engine works in this situation? Thanks

Sachin Mesare Sachin Mesare · Accepted Answer · 2016-10-17T11:00:27

I tried to deploy the workflow similar to above one, but I am not able to deploy it. Its giving me an error

org.activiti.engine.ActivitiException: Unknown property used in expression: ${variableABC == true}

then I changed it to

[CDATA[${execution.getVariable('variableABC') == true}]]

[CDATA[${execution.getVariable('variableABC') == false}]]

[CDATA[${execution.getVariable('variableABC') == null}]]

After this I was able to deploy it and run my tests successfully.

Observations:

It has never gone to "false" sequence flow when I had above 3 sequence flow
When I removed last sequence flow i.e. checking with null, I got error org.activiti.engine.ActivitiException: No outgoing sequence flow of the exclusive gateway 'exclusivegateway1' could be selected for continuing the process

So I think there is no issue with activiti. You just verify your workflow properly.

:)

Activiti bpmn - missing variable comparision to false

2 Answers