How to pass the query string parameters in the AWS API Gateway?

Question

Following is my Lambda handler which is expecting the users data from the queryStringParameters:-

export const lambdaHandler = async (event, context) => {
    try {
        const numberOfUsersRequested= (event && event.queryStringParameters.users) ? event.queryStringParameters.users : 10;
        const users = await generateUsers(numberOfUsersRequested).then(data => data.users);

I'm using AWS SAM to develop my Lambda and I can test it very well using the event.json as an input event to this Lambda locally. Here is a chunk of event.json where I'm passing the queryStringParamters users like this:-

{
  "body": "{\"message\": \"mock data\"}",
  "resource": "/{proxy+}",
  "path": "/path/to/resource",
  "httpMethod": "POST",
  "isBase64Encoded": false,
  "queryStringParameters": {
    "users": 200
  },

Now, may I know how to pass the same QueryStringParameters from the AWS API Gateway console. Currently, I'm getting this 500 error on the AWS console for the API Gateway:-

{
  "message": "Internal server error"
}

Mon Sep 28 01:24:15 UTC 2020 : Endpoint response headers: {Date=Mon, 28 Sep 2020 01:24:15 GMT, Content-Type=application/json, Content-Length=2, Connection=keep-alive, x-amzn-RequestId=0e1f110c-e80c-4ff1-870a-5cafd04167db, x-amzn-Remapped-Content-Length=0, X-Amz-Executed-Version=$LATEST, X-Amzn-Trace-Id=root=1-5f713b3d-4762f9b07ee8c1d7c6623574;sampled=0}
Mon Sep 28 01:24:15 UTC 2020 : Endpoint response body before transformations: {}
Mon Sep 28 01:24:15 UTC 2020 : Execution failed due to configuration error: Output mapping refers to an invalid method response: 200
Mon Sep 28 01:24:15 UTC 2020 : Method completed with status: 500

I have performed the following steps to mitigate the issue but not working. It looks like something is missing :- 1)Added the url query string parameters as users in the Method Request (refer screenshot)

In the Integration Request -> Mapping Templates, added the mapping as application/json:-

{ "users": "$input.params('users')" }

And finally passing the query string as users=6.

Marcin · Accepted Answer · 2020-09-28 01:53:36Z

2

In your case, the event should just be:

{
    "users": "6"
}

You can add the following to the beginning of your handler to confirm:

  console.log(JSON.stringify(event, null, 2));

Therefore, to get users value you should just use event.users, not event.queryStringParameters.users.

answered Sep 28, 2020 at 1:53

Marcin

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3 Comments

vinod827 Over a year ago

this is a code level change. Do I need to make any change on the AWS console for API Gateway when it comes to passing users and its mapping. Because with latest code deployed (as per your suggestion), I'm still getting 500 error. Any changes to be made when passing the param from API Gateway console? Please advise, thanks

Marcin Over a year ago

@vinod827 Nothing else should be required from what I can tell. But I think there is some confusion if you worry about code change. Your original event you are testing and developing for is for lambda proxy integration. But your API is for non-proxy integration. I made the answer based on the letter. I think you have to decide which integration to use, as you are using both in your question, and that's why you have these issues. btw, proxy integration is much easier and most commonly people use it for this reason.

Marcin Over a year ago

@vinod827 Also, did you print out the event using console.log? You can check its form in CloudWatch logs to confirm its real form and content.

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