How to start a process via REST-API with a "plain" JSON payload?

[Matthias Reining]

Hi all,

I was wondering how to start a process via REST-API with a "plain" JSON payload?

How to start is clear: http://docs.camunda.org/latest/api-references/rest/#process-definition-start-process-instance

My question belongs more to the "plain" JSON payload. My payload is a JSON data structure that is not structured in the "Camunda way" as {"aVariable" : {"value" : "aStringValue", "type": "String"}. There is no type information in my JSON data strucutre available -> "plain JSON".

Is there a possiblity to pass an individual JSON object? I already tried to package everything into a quoted string and pass as one variable. Unfortunately, in this case I cannot use the object in the BPMN conditions.

Different BPM processes should be started from different clients / systems (SOA landscape). At the moment, all clients have to remap the existing JSON data structure in the Camunda JSON data structure. Furthermore, I would also like to pass complete data structures (deep data structures) and not only flat data structures.

How do you normally solve this scenario?

Thanks, Matthias

[Roman Smirnov]

Hi Matthias,

Just for me to understand your request correctly:

You have a "plain" JSON object like this:

  { "x" : "abc", "y" : 123, ... }
 

And at the moment you have to transform the "plain" JSON into the "Camunda way" JSON like this:

  { "x" : { "value" : "abc" }, "y" : { "value" : 123 }, ... }
 

... so that you are able to start a process instance with variables via REST API.

Is that correct? Or what what do you mean with a "plain" JSON?

Cheers,

Roman

[Matthias Reining]

Hi Roman,

exactly!

I'd like to avoid this transformation in the client that start the process.

Thanks, Matthias

[Daniel Meyer]

Hi Matthias,

I would propose to post the json as follows:

{ "jsonInput" : { "value": "{ \"x\" : \"abc\", \"y\" : 123, ... }", "type": "String" } }

You can then use camunda Spin for evaluating conditions:

<sequenceFlow>
  <conditionExpression xsi:type="tFormalExpression">
    ${ S(jsonInput).prop("y").numberValue() > 10 }
  </conditionExpression>
</sequenceFlow>

(Json Path is also supported).

Further reading:

- http://docs.camunda.org/latest/guides/user-guide/#data-formats-xml-json-other-json

- http://docs.camunda.org/latest/api-references/spin/#handling-json

Does that help you?

Regards,

Daniel

[Matthias Reining]

Hi Daniel,

thanks! 

camunda Spin was new for me. This solution will help me for sure.

But also in this case, the client (process starter) has to quote the payload and for designing BPMN condition the BPMN designer have to know that there is a special format (in summary, not really nice...)

But, in any case, the solution you pointed out looks good and solve my problem in a more or less nice way.

Cheers, Matthias