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

You can convert any request body data into valid JSON format by configuring the mapping templates in the integration settings so that AWS Lambda can receive it.

Currently it seems Amazon API Gateway does not support application/x-www-form-urlencoded officially yet, but avilewin posted a solution to do that on the AWS forums. In the mapping templates you can use Velocity Template Language (VTL), so what you need to do is to configure mapping templates that convert application/x-www-form-urlencoded format into valid JSON format. Of course this is a dirty solution, but I think it's the only way to do that for now.

If you enable Lambda Proxy Integration

The POST body will be available from:

event['body']['param']

GET parameters and headers will also be available via

event['pathParameters']['param1']
event["queryStringParameters"]['queryparam1']
event['requestContext']['identity']['userAgent']
event['requestContext']['identity']['sourceIP']

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
  });
};