How to save a JSON-object and use it in another request? - json

Question

i'm currently trying to set up some JMeter testplans. I am pretty new to this (started a week ago) and don't have much programming experience either, so i hope you could help me in this case.
I already set up some http requests and have some simple JSON Extractor post processors to save some of the variables and use them with the "${variable}" notation.
But now i need to save and modify an object from a response to use that in the next http request.
My respose is a extremely big JSON object and the part im interested in looks something like this:
{
"payload": {
"workspace": {
"resultInstance": [
[{"part": "1"...}],
[{"part": "2"...}],
...
[{"part": "20"...}]
]
}
}
}
Note that for whatever reason these objects {"part":"1"...} are inside a nested array. And they are also pretty big.
I would like to safe those objects in a variable to use them in my next http request which should looks like this:
{
"instanceChange": {
"functionChecks": [
{"part": "1"...},
{"part": "2"...},
...
{"part": "20"...}
]
}
}
So what im really trying to find is a way to save all of the possible objects inside the nested array "resultInstance" and put them inside the non nested array "functionChecks".
I already looked inside the JMeter documentation but because of my poor programming background i cant find a way to realize this.
I think i need something like the JSR223 PostProcessor and "simply go through the resultInstance-array and use smth. like an getObject() on these", but i cant figure out the code i need and if its even possible to safe objects in variables in Jmeter.
Im pretty thankful for every bit of help or advice :).
Thanks in advance,
aiksn

Answer 1

Add JSR223 PostProcessor as a child of the request which returns the JSON response
Put the following code into "Script" area:
def response = new groovy.json.JsonSlurper().parse(prev.getResponseData())
def request = ['instanceChange': ['functionChecks': response.payload.workspace.resultInstance]]
vars.put('request', new groovy.json.JsonBuilder(request).toPrettyString())
That's it, you should be able to refer the generated request body as ${request} where required
More information:
Apache Groovy - Parsing and producing JSON
Apache Groovy - Why and How You Should Use It

Answer 2

let response ={
"payload": {
"workspace": {
"resultInstance": [
[{"part": "1"...}],
[{"part": "2"...}],
...
[{"part": "20"...}]
]
}
}
};
let requestObj={
"instanceChange": {
"functionChecks": [
]
}
};
response.payload.workspace.resultInstance.forEach(myFunction);
myFunction(item, index) {
requestObj.instance.functionsCheck.push(item[0]);
}