How to get only form variables of Camunda's human task using REST API? - camunda

Question

I have a simple bpmn with only script task that sets a process variable and a human task that accepts two input parameters, one output parameter and has defined one form data field.
After I start the process the execution stops on the human task. I'm then trying to obtain the variables of the human task form (i.e. the input variables and\or the form data field but not the execution variable set by the screen task).
The results of querying REST API are as follows:
task/id/variables - input variables and script task variable
task/id/form-variables - input variables, form data field and script task variable
task/id/localVariables - empty
I can't understand why the script task variable is returned along with other form-variables.
How can I obtain only the input variables and form data field but not the screen task variable (and possibly all other process variables)?
EDIT: I don't want to use query parameters to select variable names.
I'm using the Camunda Widlfly 10.0.0.
The bpmn I'm using:
<?xml version="1.0" encoding="UTF-8"?>
<bpmn:definitions xmlns:bpmn="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:di="http://www.omg.org/spec/DD/20100524/DI" xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" xmlns:camunda="http://camunda.org/schema/1.0/bpmn" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" id="Definitions_1" targetNamespace="http://bpmn.io/schema/bpmn" exporter="Camunda Modeler" exporterVersion="1.3.0">
<bpmn:process id="userTaskExample" isExecutable="true">
<bpmn:startEvent id="StartEvent_02mu30n">
<bpmn:outgoing>SequenceFlow_14v3dyf</bpmn:outgoing>
</bpmn:startEvent>
<bpmn:endEvent id="EndEvent_144sl4n">
<bpmn:incoming>SequenceFlow_0acu0wh</bpmn:incoming>
</bpmn:endEvent>
<bpmn:sequenceFlow id="SequenceFlow_0acu0wh" sourceRef="Task_096f7n7" targetRef="EndEvent_144sl4n" />
<bpmn:userTask id="Task_096f7n7" name="user task sk">
<bpmn:extensionElements>
<camunda:formData>
<camunda:formField id="form_1" label="form_1" type="string" defaultValue="form_1_" />
</camunda:formData>
<camunda:inputOutput>
<camunda:inputParameter name="input_1">input_1_val</camunda:inputParameter>
<camunda:inputParameter name="input_2">input_2_val</camunda:inputParameter>
<camunda:outputParameter name="output_1">output_2</camunda:outputParameter>
</camunda:inputOutput>
</bpmn:extensionElements>
<bpmn:incoming>SequenceFlow_0sulfwg</bpmn:incoming>
<bpmn:outgoing>SequenceFlow_0acu0wh</bpmn:outgoing>
</bpmn:userTask>
<bpmn:sequenceFlow id="SequenceFlow_14v3dyf" sourceRef="StartEvent_02mu30n" targetRef="Task_0cphzp1" />
<bpmn:sequenceFlow id="SequenceFlow_0sulfwg" sourceRef="Task_0cphzp1" targetRef="Task_096f7n7" />
<bpmn:scriptTask id="Task_0cphzp1" name="script task sk" scriptFormat="groovy" camunda:resultVariable="script_task_variable">
<bpmn:incoming>SequenceFlow_14v3dyf</bpmn:incoming>
<bpmn:outgoing>SequenceFlow_0sulfwg</bpmn:outgoing>
<bpmn:script><![CDATA["scipt task variable"]]></bpmn:script>
</bpmn:scriptTask>
</bpmn:process>
<bpmndi:BPMNDiagram id="BPMNDiagram_1">
<bpmndi:BPMNPlane id="BPMNPlane_1" bpmnElement="userTaskExample">
<bpmndi:BPMNShape id="StartEvent_02mu30n_di" bpmnElement="StartEvent_02mu30n">
<dc:Bounds x="151" y="66" width="36" height="36" />
<bpmndi:BPMNLabel>
<dc:Bounds x="169" y="102" width="0" height="0" />
</bpmndi:BPMNLabel>
</bpmndi:BPMNShape>
<bpmndi:BPMNShape id="EndEvent_144sl4n_di" bpmnElement="EndEvent_144sl4n">
<dc:Bounds x="616" y="66" width="36" height="36" />
<bpmndi:BPMNLabel>
<dc:Bounds x="634" y="102" width="0" height="0" />
</bpmndi:BPMNLabel>
</bpmndi:BPMNShape>
<bpmndi:BPMNEdge id="SequenceFlow_0acu0wh_di" bpmnElement="SequenceFlow_0acu0wh">
<di:waypoint xsi:type="dc:Point" x="433" y="84" />
<di:waypoint xsi:type="dc:Point" x="524" y="84" />
<di:waypoint xsi:type="dc:Point" x="524" y="84" />
<di:waypoint xsi:type="dc:Point" x="616" y="84" />
<bpmndi:BPMNLabel>
<dc:Bounds x="539" y="84" width="0" height="0" />
</bpmndi:BPMNLabel>
</bpmndi:BPMNEdge>
<bpmndi:BPMNShape id="UserTask_1lppvq8_di" bpmnElement="Task_096f7n7">
<dc:Bounds x="333" y="44" width="100" height="80" />
</bpmndi:BPMNShape>
<bpmndi:BPMNEdge id="SequenceFlow_14v3dyf_di" bpmnElement="SequenceFlow_14v3dyf">
<di:waypoint xsi:type="dc:Point" x="169" y="102" />
<di:waypoint xsi:type="dc:Point" x="169" y="133" />
<di:waypoint xsi:type="dc:Point" x="252" y="133" />
<di:waypoint xsi:type="dc:Point" x="192" y="204" />
<di:waypoint xsi:type="dc:Point" x="275" y="204" />
<di:waypoint xsi:type="dc:Point" x="275" y="284" />
<bpmndi:BPMNLabel>
<dc:Bounds x="222" y="153.5" width="0" height="0" />
</bpmndi:BPMNLabel>
</bpmndi:BPMNEdge>
<bpmndi:BPMNEdge id="SequenceFlow_0sulfwg_di" bpmnElement="SequenceFlow_0sulfwg">
<di:waypoint xsi:type="dc:Point" x="325" y="331" />
<di:waypoint xsi:type="dc:Point" x="401" y="342" />
<di:waypoint xsi:type="dc:Point" x="383" y="204" />
<di:waypoint xsi:type="dc:Point" x="383" y="124" />
<bpmndi:BPMNLabel>
<dc:Bounds x="392" y="258" width="0" height="0" />
</bpmndi:BPMNLabel>
</bpmndi:BPMNEdge>
<bpmndi:BPMNShape id="ScriptTask_1q3eqsu_di" bpmnElement="Task_0cphzp1">
<dc:Bounds x="225" y="284" width="100" height="80" />
</bpmndi:BPMNShape>
</bpmndi:BPMNPlane>
</bpmndi:BPMNDiagram>
</bpmn:definitions>

Answer 1

Your results suggest you are displaying the variable defined in the script task in the human task form.
I say this because when you look at the source to retrieve the form variables we see:
// first, evaluate form fields
TaskDefinition taskDefinition = task.getTaskDefinition();
if (taskDefinition != null) {
TaskFormData taskFormData = taskDefinition.getTaskFormHandler().createTaskForm(task);
for (FormField formField : taskFormData.getFormFields()) {
if(formVariableNames == null || formVariableNames.contains(formField.getId())) {
result.put(formField.getId(), createVariable(formField, task));
}
}
}
// collect remaining variables from task scope and parent scopes
task.collectVariables(result, formVariableNames, false, deserializeObjectValues);
Notice we ierate over the form field definition to retrieve the variable names we care about, then we populate the data from the execution context.
Ultimately Activiti/Camunda (they are 90% the same at the engine level) does no differentiate between data entered in a form and data created in a script or service task (e.g. as a result variable).
If you need to separate these for some reason, I suggest you use a naming convention and query process variables based on the variable name convention.