In Activiti, how do I check if a variable is set?

Question

For example I have a workflow which can start immediately or with a delay (startTime variable).

Right after the startEvent I have an exclusiveGateway where I check if the flow should go on or wait until startTime.

<exclusiveGateway id="startGateway" default="startSequenceFlow3"/>
<sequenceFlow id="startSequenceFlow1" sourceRef="startGateway" targetRef="startTimer">
    <conditionExpression xsi:type="tFormalExpression"><![CDATA[${startTime != null}]]></conditionExpression>
</sequenceFlow>

Starting the workflow passing a variable startTime works fine, but passing no startTime throws an exception:

Cannot resolve identifier 'startTime'

What would be the best way to check if startTime is set, since startTime != null is not working? I would prefer not to pass a startTime at all (not startTime=null).

Code that I use including the variable:

variables.put("startTime", startTime);
ProcessInstance instance = runtimeService.startProcessInstanceByKey(processKey, variables);

or without:

ProcessInstance instance = runtimeService.startProcessInstanceByKey(processKey, variables);

Instead of not setting `startTime` at all, you could set it to a special value, for example `NONE`, and then check in the process if it's set to `NONE` to decide what to do. — Jesper, May 31 '16 at 14:15

score 16 · Accepted Answer · answered Jan 17 '17 at 13:58

16

Use the following expression:

${execution.getVariable('startTime') != null}

answered Jan 17 '17 at 13:58

Martin

176
1
2

IMO this is the best answer. – Steffen Harbich Aug 15 '17 at 11:12
4

There is also a method `execution.hasVariable('startTime')` available. – Steffen Harbich Jun 11 '19 at 07:53

score 2 · Answer 2 · answered Jun 01 '16 at 13:12

You have to set startTime variable in both cases;

variables.put("startTime", startTime);
ProcessInstance instance = runtimeService.startProcessInstanceByKey(processKey, variables);

and

variables.put("startTime", null);
ProcessInstance instance = runtimeService.startProcessInstanceByKey(processKey, variables);

Then check variable in gateway

<exclusiveGateway id="startGateway" default="waitSequenceFlow"/>
<sequenceFlow id="startSequenceFlow" sourceRef="startGateway" targetRef="firstTask">
    <conditionExpression xsi:type="tFormalExpression"><![CDATA[${empty startTime}]]></conditionExpression>
</sequenceFlow>
<sequenceFlow id="waitSequenceFlow" sourceRef="startGateway" targetRef="startTimer"/>

OR

You can use http://www.activiti.org/userguide/#bpmnTimerStartEvent

Yes I know that I can set the variable to `null`. I would prefer to have a method where I do not have to set the variable. For example I have two GUIs and each of them fills in only the variables it provides, meaning that in GUI1 are different variables than in GUI2. I upvoted, but can't mark it as answer. — flavio.donze, Jun 01 '16 at 13:30
You can add ServiceTask before Gateway, which check if variable is set and if not, then set it with null. — fersmi, Jun 02 '16 at 06:00

In Activiti, how do I check if a variable is set?

2 Answers2