Extracting value from Json response of POST request in Jmeter using Json Extractor

Question

Post request Json Extractor Get request debug sampler error message I'm using Jmeter for stress testing of my application. Test plan that I'm building has a POST request which creates a user and the next PATCH request updates it. Basically I want to extract user_id from Json response received after POST request and add that id in the body of the next request. For that I use Json extractor in my POST request and when I check Debug Sampler the value is successfully stored. But when I try to use extracted user_id in any subsequent requests of the same thread it is not recognized. However when I tried to extract user_id of already created user with GET request then this user_id is normally recognized by other requests. I'm not sure whether Json extractor is not normally used with POST requests or I'm doing something wrong.

Answer 1

It's impossible to provide an answer without seeing the screenshot of your Test Plan or even better Schematic View (the option is available under "Tools" main menu entry since JMeter 5.1)

Given you're able to see the extracted value in the debug sampler I can think of 2 possible options:

1. Your syntax of referring the user_id variable is wrong, in JMeter the Variables are accessed like ${user_id}
2. Placement of your JSON Extractor is wrong, i.e. instead of putting it as a child of a specific sampler you have it at the same level as all Samplers therefore it's getting applied to the Debug Sampler as well and the extracted value gets overwritten. See Scoping Rules user manual section for more information