Jmeter aggregate certain response values from json to use in next request - json

Question

I have the following response coming from a request
[
{
"id": 3767,
"sellerName": "abc",
"siteActivity": [
{
"siteId": -1,
"siteName": "example.com",
"categories": [
{
"categoryId": 79654,
"parentId": null,
"name": "Photo & Picture Frames",
"siteName": null,
"channelType": null
},
{
"categoryId": 114397,
"parentId": null,
"name": "Chests of Drawers",
"siteName": null,
"channelType": null
},
{
"categoryId": 11707,
"parentId": null,
"name": "Jewellery Boxes",
"siteName": null,
"channelType": null
},
{
"categoryId": 45505,
"parentId": null,
"name": "Serving Trays",
"siteName": null,
"channelType": null
}
]
}
]
},
{
"id": 118156,
"sellerName": "xyz",
"siteActivity": [
{
"categoryId": 45505,
"parentId": null,
"name": "Serving Trays",
"siteName": null,
"channelType": null
}
]
}
]
Now, I need to extract "id" values and "categoryId" values and send them as list in the next request body.
Currently, I am using JSON Path Extractor with the expression
$.[*].id
to get my hand on all ids and
$.[*].siteActivity.[categoryId]
for category ids.
Next, I want to use the above values and send them as parameters in request body.
Currently, I am able to extract only one id with
$.[0].id
and then assigning it to variable "id" and using the following in request body
{"ids":[{"id":"${id}"}]}
but I want to be able to send
{"ids":[{"id":"${id}"},{"id":"${id2}"}....]}
There is no limit on how many ids can be there, so I cannot hardcode and need something dynamic to do the aggregation. What kind of processor can help me here? Please add some example if you can.

Answer 1

I believe that you should be able to use Beanshell PostProcessor for building the request.
Given your sample data your $.[*].id JSONPath Expression should return the following values:
id=[3767,118156]
id_1=3767
id_2=118156
So basically you need to:
Determine "id" count
Populate dynamic JSON Object to send
Store it to JMeter variable for later use
In order to do so add a Beanshell PostProcessor after JSONPath Extractor and put the following code into its "Script" area
import net.sf.json.JSONArray;
import net.sf.json.JSONObject; // necessary imports
JSONObject data2Send = new JSONObject();
JSONArray array = new JSONArray(); // instantiate JSON-related classes
int idCount = vars.get("id").split(",").length; // get "id" variables count
for (int i = 1; i <= idCount; i++) { // for each "id" variable
JSONObject id = new JSONObject(); // construct a new JSON Object
id.put("id", vars.get("id_" + i));// with name "id" and value id_X
array.add(id); // add object to array
}
data2Send.put("ids",array); // add array to "ids" JSON Object
vars.put("myJSON", data2Send.toString()); // store value as "myJSON" variable
You can refer to your {"ids":[{"id":"3767"},{"id":"118156"}]} data as ${myJSON} where required.
The approach will play for any number of "id" variables.
References:
Welcome to Json-lib
How to use json-lib
Json-lib JavaDoc
How to use BeanShell: JMeter's favorite built-in component