Conversion of the outcome of a business rule task in the external task worker (node.js)

Hi all,

I followed the example of the website ( and use as an external task worker.

Before the corresponding process (P2), I check a few rules in a business rule task using DMN (P1). As a result of P1 I get a list (Process P1 = Business Rule Task; Result Variable = “myOutput”, Map Decision Result = collectEntries).

In P2, a service task, I now want to use the result list from “myOutput” in an external task worker using node.js. In the Camunda Cockpit I can see that this variable is of type “Object”, the value is a “java.util.ArrayList” in Serialization Data Format = “application/x-java-serialized-object”.

Can someone explain how I can use this list in my external task worker? If I follow the example of the web page (const myOutput = task.variables.getTyped(‘myOutput’);), then I only get the serialized value of type “Object”. I don’t know how to deserialize it in node.js.

Since I haven’t found an entry elsewhere yet, the solution is probably obvious, but unfortunately I don’t see it.

Thank you for your help,

P.S.: Note: If I only have a single value in the output of P1 (Map Decision Result = singleResult), I get the deserialized value directly and can work with it. Only in case of “Map Decision Result = collectEntries” I get a serialized object.



you could simply set the default serialization format of the engine to JSON. Do it as described here for Spring Boot:

or put that into your application server config:




Of course, the serialization format can also be changed for each variable individually, but in your case that would imply to “rewrap” the result of the DMN execution (see

Best, Ragnar

Hi Ragnar,

Unfortunately I haven’t understood it yet, I think.

Does this mean that I can’t do the deserialization directly in node.js?

When calling the REST API, I can specify that the objects are delivered deserialized:

“deserializeValues”: true

Do I understand you correctly that I cannot do this with node.js and have to configure the deserialization in the server?

Maybe I didn’t get it right either.

I look forward to your hints.

Thank you

Any further ideas?

Does anyone have another idea how I can enable deserialization in node.js?

OK, sometimes I need a little time to understand it.

But now and after a little research on defaultSerializationFormat I have made the appropriate property in the engine configuration (bpm-platform.xml) and now get my output values in JSON format.

Many thanks for the hint, Ragnar.

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@camORo hi , i have the same issue
i try to add those properties to bpm-platform.xml to be able to have only json not a serialized object


but everytime i add those properties to file , the engine refuse to start without any error
so how do you get json format ??
and here is a link to my issue : Deserialize map type in javascript

You can set a input parameter with the javascript code:


it serialize the java object and you can use it inside the node worker