Custom header values for service task - complex BPMN2 extensions


all our extension fields for standard Flowable FlowNode are primitive expression values, which extend the FlowNodes via BPMN2 extension Elements. Upon runtime, when the corresponding behaviors/delegates get called, the relevant values get injected as org.flowable.common.engine.api.delegate.Expression where required.

Is it possible to specify complex extension elements like a list with name/value pairs? If not is there another way?



Hey @tina.bandalo,

The extension elements are extremely flexible and you can provide nested structures as you want.

As an example have a look at


Hi @filiphr,

thanks a lot for the answer. I want to follow-up on Tinas question.

How exactly would I store a list of key-value pairs in the extension then?

Let´s assume I have the following ordered key-value list:

1 = January
2 = February
3 = March

How would I store these pairs as part of the extension elements?


Hey @Rouvenday,

The way you want to store this is entirely up to you.

There are multiple ways to store it e.g.

<flowable:monthPair key="1" value="January" />
<flowable:monthPair key="2" value="February" />
<flowable:monthPair key="3" value="March" />


    <month key="1" value="January" />
    <month key="2" value="February" />
    <month key="3" value="March" />

When you have a control over the creation of the BpmnModel it is entirely up to you to decide how you want to store it.


Hi @filiphr,

Thanks a lot.

Is it also possible to inject complex structures into the field of the delegated class?

Something similar to this (pseudo xml):

<flowable:field name="months">
    <flowable:field name="1" expression="${firstMonth}" />
    <flowable:field name="2" expression="${secondMonth}" />
    <flowable:field name="3" expression="${thirdMonth}" />

Best Regards,