how to design dynamic response in mock server - dynamic

Question

I'm now using the mock server from https://www.mock-server.com/ and run it in a docker container.
Now I would like to let the response change as request body changes. I've looked up for dynamic response on official webiste for a while, but have no idea on how to extract specific data from request body.
curl -v -X PUT "http://localhost:1080/mockserver/expectation" -d '{
"httpRequest": {
"path": "/some/path"
},
"httpResponseTemplate": {
"template": "return { statusCode: 200, body: request.body };",
"templateType": "JAVASCRIPT"
}
}'
The code above is to create a simple expectation, which will response the request body. For example,
$curl http://localhost:1080/some/path -d '{"name":"welly"}'
{"name":"welly"} //response
Now I want to change the way of giving the response. For example, I would like to input {a:A, b:B} and get the response {a:B, b:A}.
So, how to modify the json data in request body and give it to response? I guess there are some methods to extract specific data from json file, or modify json data, etc. Also, I want to know how to better search the detailed information, since the official website and full REST API json specification
(https://app.swaggerhub.com/apis/jamesdbloom/mock-server-openapi/5.11.x#/expectation/put_expectation) is hard for me to understand.
Thanks a lot!

Answer 1

I needed to do this as well, I think I got this to work have a look at my curl example for the expectation I hope that helps:
curl -v -X PUT "http://localhost:1080/mockserver/expectation" -d '{
"httpRequest": {
"path": "/api/fun",
"method": "POST"
},
"httpResponseTemplate": {
"template": "
req = JSON.parse(request.body.string)
rid = req[\"id\"]
return { statusCode: 201, body: {new_id: rid} }
",
"templateType": "JAVASCRIPT"
}}'
After you do this if send:
curl -X POST http://localhost:1080/api/fun --data '{"id": "test_1"}'
it should return:
{ "new_id" : "test_1" }
Javascript templating supported via Nashorn engine and thus will no longer be available from Java 15. Here is the note from the Mockserver docs.
From Java 15 Nashorn is no longer part of the JDK but it is available as a separate library that requires Java 11+. Once MockServer minimum Java version is 11 then this separate library will be used.