How can I get raw body string in Lambda (API gateway Lambda proxy)

After enabled CORS on API gateway, here is the request I sent to the http end point:

    type: 'put',
    url: '',
    data: {params: {param1: "543543", param2: "fdasghdfghdf", test: "yes"}},
    success: function(msg){
    error: function(msg){

Here is the lambda function(I’m using node serverless package, and no mistakes on the code):

module.exports.julian_test = (event, context, callback) => {

var response_success = {
statusCode: 200,
headers: {
    "Access-Control-Allow-Origin": "*"
body: JSON.stringify({
    firstUser: {
        username: "Julian",
        email: "awesome"
    secondUser: {
        username: "Victor",
        email: "hello world"
    thirdUser: {
        username: "Peter",
        email: "nice"
callback(null, response_success);

The console.log(event.body) logs out : params%5Bparam1%5D=543543&params%5Bparam2%5D=fdasghdfghdf&params%5Btest%5D=yes

, which is not the format I want. I checked the OPTIONS Integration Request / body mapping template, here is the snapshot.

I tried to delete the “application/json” but after that I receive the following response:

XMLHttpRequest cannot load Response to preflight request doesn’t pass access control check: No ‘Access-Control-Allow-Origin’ header is present on the requested resource. Origin ‘null’ is therefore not allowed access. The response had HTTP status code 500.

Does anyone know how to get a raw string request body in the back-end lambda? Please help!

Do you have CORS set in serverless.yml. cors: true

  name: aws
  runtime: nodejs4.3

    handler: handler.hello
       - http:
           path: hello
           method: get
           cors: true

@panorart It looks like you’re using jQuery for your AJAX request. The jQuery docs state that data is converted to a query string unless it’s already a string.

Are you trying to pass this as a JSON object? If you are then try using data: JSON.stringify({params: {param1: "543543", param2: "fdasghdfghdf", test: "yes"}}).

You’ll need to use JSON.parse(event.body) in your Lambda to convert the string back to a JSON object.