Grails HTTPBuilder not working with variable in body

Question

I am writing a code in grails which is making a post call using httpbuilder. everything works fine if I hardcode the values for body but when I pass the same using variables, then it keep giving me -

Unprocessable Entity. Stacktrace follows:
Message: Unprocessable Entity
   Line | Method
->> 636 | defaultFailureHandler in groovyx.net.http.HTTPBuilder
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
|   492 | doRequest             in     ''
|   427 | doRequest . . . . . . in     ''
|   376 | request               in     ''

The code is like below -

    def input = "s3://in_folder/inputFile.mp3"
    def outFile = "outFile.m3u8"
    def http = new HTTPBuilder("https://app.gridserver.com")
    http.request( groovyx.net.http.Method.POST, groovyx.net.http.ContentType.JSON ) { req ->
        uri.path = 'api/v2'
        headers.Accept = 'application/json'
        headers.'Key' = "ssdflkjdf8338fdjsd"
        body = ["input": input,  
            "output":[  "filename": outFile,
                        "format": "mp3",
                ] ]

        response.success = { resp, reader ->
            println "Got response: ${resp}"
        }
    }
}

If I replace the variables "input and outFile" here with the actual value then it works fine.

Answer 1

ok, I seems to have solved it finally. I needed to do the .toString() in the expression so that it takes it like a literal and dont convert it into a json. so finally I wrote it like "s3://audio_in/${fileName}.mp3".toString() and it works fine.