How to parse Json data which is in the HTTP post request in JMeter

Question

Here is the Json Data:

filterKeys":{"${FilterGroup}":["Phenols"]},"lastFilterGroup":"${FilterGroup}"}

I have to extract phenols from the post request for every filter group this value changes.

Answer 1

Since request payloads have to be composed by yourself, it doesn't make much sense to extract data from there. Makes sense, instead, to fill them with data you take/populate from somewhere.

What could easily be done then, is to populate the request body with variables, so your request body may look like this:

{  
   "keyword":"${Keyword}",
   "maxlength":25,
   "offset":0,
   "sortKeys":{  
      "ascending":false,
      "attributeName":"relevance",
      "type":"ATTRIBUTE"
   },
   "filterKeys":{  
      "${filter_key}":[  
         "${filter_value}"
      ]
   },
   "lastFilterGroup":"${filter_key}"
}

And add a JSR223 PreProcessor (using groovy) to that request sampler, where to put values for those variables, like:

vars.put('filter_key', 'analyte');
vars.put('filter_value', 'Phenols');

Otherwise, if you want to extract "analyte" and "Phenol" from that JSON body, given it is a response, you can add a JSON Extractor to the sampler and use the following path expressions

$.filterKeys

to get

[
  {
    "analyte": [
      "Phenols"
    ]
  }
]

and

$.filterKeys.analyte.*
// or
$.filterKeys.${filter_key}.*

to get

[
  "Phenols"
]

or other combinations that you can try out on several websites like this.