how to calculate length of JSON array using JMeter?

Question

I am using Jmeter to make an API call. The response is:

{
  "qid": [
    {
      "id": "88e4b027b72f793d3c",
      "created": 1410955125065
    },
    {
      "id": "54197788e4",
      "created": 1410955125065
    },
    {
      "id": "788e4",
      "created": 1410955125065
    },
    {
      "id": "5419778",
      "created": 1410955125065
    },
    ....
  ]
}

The length of the JSON array varies for different API requests. How do I determine the length of the JSON array?

Answer 1

JMeter has Beanshell post processors.

So import Java JSON parser.

import org.json.*;
JSONObject jsonObj = new JSONObject(prev.getResponseDataAsString());
JSONArray jsonQid = jsonObj.getJSONArray("qid");
//jsonQid.length  --> should print the array length

Answer 2

A more simple approach is to use the "Content-Length" header parameter.

Remember that this value stands for the actual body length, after compression, if any.

Answer 3

String response = prev.getResponseDataAsString();
JSONParser parser = new JSONParser();
JSONArray arrayJson = (JSONArray) parser.parse(response);
String size = arrayJson.size().toString();

Answer 4

I found using the JSON Path Postprocessor even easier with the latest version of JMeter. In your example, add the following JSON path expression: $.qid.*.id.

Add a debug sampler with a listener to your script. After the script is run, the variable qid_matchNr will be equal to the size of the JSON array you are interested in. That variable will be available to use with your script.