Can't pass extracted string into body object in JMeter

Question

I am trying to pass a string extracted from an API response in a subsequent call in JMeter. I am able to extract the object I want ("thing": "THING"), store it as variable $thisThing and then pass it, but not as a string.

Using this as my body data:

{
    "foo": "bar",
    "thing": ${thisThing}
}

...results in this request body:

{
    "foo": "bar",
    "thing": THING,
}

And the API errors out, unexpected token. Looking into post-processing solutions but I can't dig up anything of relevance.

Answer 1

As per JSON Object Literals:

Keys must be strings, and values must be a valid JSON data type:

• string
• number
• object
• array
• boolean
• null

so if this THING supposed to be a JSON String - you need to surround it with quotation marks:

{
    "foo": "bar",
    "thing": "${thisThing}"
}

or amend your Post-Processor configuration to extract the THING value along with surrounding quotation marks.

You might also need to add a HTTP Header Manager and configure it to send Content-Type header with the value of application/json