How to pass a params from POST to AWS Lambda from Amazon API Gateway

Question

In this question How to pass a querystring or route parameter to AWS Lambda from Amazon API Gateway

shows how to map query string params to AWS lambda using API gateway. I would like to do the same but mapping POST values instead of query-string. I tried:

{
    "values": "$input.params()"
}

but did not work, I don't see the actual form data. BTW I am posting using:

application/x-www-form-urlencoded

I get my response from my lambda function, so I know it is invoking lambda fine, but my problem is that I don't see the POST params anywhere. I can;t figure out how to map them. I dump all I get on Lambda side and here it is:

 {"values":"{path={}, querystring={}, header={Accept=*/*, Accept-Encoding=gzip, deflate, Accept-Language=en-US,en;q=0.8, Cache-Control=no-cache, CloudFront-Forwarded-Proto=https, CloudFront-Is-Desktop-Viewer=true, CloudFront-Is-Mobile-Viewer=false, CloudFront-Is-SmartTV-Viewer=false, CloudFront-Is-Tablet-Viewer=false, CloudFront-Viewer-Country=US, Content-Type=application/x-www-form-urlencoded, Origin=chrome-extension://fhbjgbiflinjbdggehcddcbncdddomop, Postman-Token=7ba28698-8753-fcb1-1f48-66750ce12ade, Via=1.1 6ba5553fa41dafcdc0e74d152f3a7a75.cloudfront.net (CloudFront), X-Amz-Cf-Id=sc8C7dLcW0BHYopztNYrnddC0hXyFdBzHv0O9aWU1gKhd1D_J2HF3w==, X-Forwarded-For=50.196.93.57, 54.239.140.62, X-Forwarded-Port=443, X-Forwarded-Proto=https}}"}

Answer 1

Good answer by r7kamura. Additionally Here's an example of an understandable and robust mapping template for application/x-www-form-urlencoded that works for all cases (assuming POST):

{
    "data": {
        #foreach( $token in $input.path('$').split('&') )
            #set( $keyVal = $token.split('=') )
            #set( $keyValSize = $keyVal.size() )
            #if( $keyValSize >= 1 )
                #set( $key = $util.urlDecode($keyVal[0]) )
                #if( $keyValSize >= 2 )
                    #set( $val = $util.urlDecode($keyVal[1]) )
                #else
                    #set( $val = '' )
                #end
                "$key": "$val"#if($foreach.hasNext),#end
            #end
        #end
    }
}

It would transform an input of

name=Marcus&email=email%40example.com&message=

into

{
    "data": {
                "name": "Marcus",
                "email": "[email protected]",
                "message": ""
    }
}

A Lambda handler could use it like this (this one returns all input data):

module.exports.handler = function(event, context, cb) {
  return cb(null, {
    data: event.data
  });
};