REST message JSON

[Michal_S]

Hi community.

I would like to ask what would be the best solution to receive a REST message with a JSON data which might surpass the constraint of 4000 characters.

I have tried to escape json like this and it works:

{
“messageName”: “Message_28ot9tb”,
“businessKey”: “businessKey”,
“processVariables” : {
“aVariable” : {“value” : “ESCAPEDJSON”, “type”: “Json”}
}
}

but somehow I dont think this is the best solution,

Thx for any adiice.

M.

[thorben]

Hi Michal,

Using the Json variable type sounds like a decent solution to me.

Cheers,
Thorben

[StephenOTT]

@Michal_S

https://docs.camunda.org/manual/7.8/user-guide/data-formats/json/

https://docs.camunda.org/manual/7.8/reference/spin/json/01-reading-json/

[Michal_S]

Thnk you @thorben @StephenOTT
for the quick answer.

If I am not mistaken It basically means that in case sender of a REST message cant for some reason Escape a JSON then the only other option is to store a payload in a file and afterwards read payload as SPIN.

thx

[StephenOTT]

@Michal_S you can use a script in your BPMN to escape the json.

Javascript:
S(JSON.stringify(response))

[Michal_S]

@StephenOTT thx for the suggestion.
I have been reading a lot about spin/josn today as I am still a newbie here. But I cant still find a way how to convert let say a string which came via REST with more than 4000 characters to json/spin, so I can meaningfully work with it.

[StephenOTT]

In your output parameter in your HTTP-Connector configuration set the type of Script and use Javascript: Then execute the script from above.
Then you can save your SPIN. So something like

var mySpin = S(JSON.stringify(response))
execution.setVariable('myResponse', mySpin)

Then when you get that variable somewhere else like in a expression or other scripts you can do

expression example:

${myResponse.prop('myKey').value()}

assuming your json looks like

{
   "myKey": "myValue"
}

then the expression would eval to a value of myValue.

see:

Deploying External Scripts with Camunda REST API

and

Deploying Embedded Forms with Camunda REST API

[Michal_S]

thank you again for the answers
the answers are easily understandable
But I am strugling with parsing JSON

I did put
the a mockup json online
http://www.mocky.io/v2/5ac4fad12f00005300f5fcd1

and tried multiple javascript in order to play with the json data but cant get it right

thx for any advice

[StephenOTT]

@Michal_S what is the error you are receiving in the console?

[Michal_S]

@StephenOTT
I have tried many things and got diffrent resulte
but the last one is
Could not apply modification :
Unable to evaluate script: ReferenceError: “execution” is not defined in at line number 2

[StephenOTT]

You have to use “connector” instead of “execution”. Execution is not available: https://docs.camunda.org/manual/7.8/user-guide/process-engine/scripting/#variables-available-during-script-execution

Please make sure to always post your error messages. Can troubleshoot much faster.

[Michal_S]

@StephenOTT
works like a charm
thx

[Michal_S]

sorry for bringing this up again and again
basically what I did is
I did successfully import big chunk of json via rest http connector but not stringified
in case I try to stringify I immediately get some kind of errors like

var mySpin = S(JSON.stringify(response));
connector.setVariable(‘var1’, mySpin)
gives
java.util.TreeMap cannot be cast to java.lang.String
or
SPIN-01004 No matching data format detected

change of json array to just plain json {}
var mySpin = JSON.stringify(response);
connector.setVariable('holidays3 ', mySpin)

ENGINE-03083 Exception while executing Batch Database Operations with message ’

Error flushing statements. Cause: org.apache.ibatis.executor.BatchExecutorException:

org.camunda.bpm.engine.impl.persistence.entity.HistoricVariableInstanceEntity.insertHistoricVariableInstance
(batch index #1) failed.
Cause: java.sql.BatchUpdateException: Data truncation: Data too long for column ‘TEXT_’

what do I aim is to do some jsonpath very similiary like

Is it possible to manipulate a Json object with the Spin API?

I have a script task which creates a Json object. var data = [ { "value": 1 } ] S(JSON.stringify(data)) Now I’ll try to change a property of this object. var json = execution.getVariable("dataSource"); json.jsonPath("$[0]").element().prop("value", 2) json But this doesn’t work. The value is still 1. Is there another possibility to change the value of an existing Json object, and then use this manipulated Json in the rest of the definition?

but it seems it wouldnt be possible without stringify… then elements…

Can you please confirm ?

MANY thanks

[StephenOTT]

Strings have a limit in the database of 4000 characters.
YOu need to keep your object as a SPIN JSON which will be stored as a object/byte array/blob and therefore not have the limit of the 4000 characters.

When you stringify you should only be doing this in-memory/within the script or when you need to same more simple data (within 4k characters)

Why do you want to save your JSON as a string?

[Michal_S]

It is not that I want to work with JSON as a string.
What do I aim is to work with JSON using tools like jsonpath, ( elements) .
Which basically means to do it in-memory, if I am not mistaken

Thank you

[StephenOTT]

@Michal_S use the SPIN library to do the Json patch query. And keep your Json as a spin object whenever saving as a variable.

https://docs.camunda.org/manual/7.8/reference/spin/json/03-querying-json/