Can't read query parameter in AWS

Question

I am wanting to pass a query parameter from API Gateway into AWS Lambda but I am always receiving null values.

Here's my Lambda function which I merely want to return the value of http://foo.bar?name=Dan

'use strict';

exports.handle = (context, event, callback) => {
  callback(null, event.name);
}

In API Gateway I have done the following:

Create a Resource
Create a Method (GET)
Selected the correct Lambda function
Selected my GET method and clicked on Integration Request
Selected Body Mapping Templates
Set Content-Type to application/json
Added {"name": "$input.params('name')" }
Save and deploy!

However, when I load up my API the value of event.name is always null. Accessing the API is done via ...amazonaws.com/beta/user?name=dan

Edit: I've tried the accepted answer here but after simply returning the event in the callback, I only receive this data:

{
  "callbackWaitsForEmptyEventLoop": true,
  "logGroupName": "",
  "logStreamName": "",
  "functionName": "",
  "memoryLimitInMB": "",
  "functionVersion": "",
  "invokeid": "",
  "awsRequestId": "",
  "invokedFunctionArn": ""
}

I have omitted the values.

score 3 · Accepted Answer · answered Oct 05 '17 at 09:28

3

The function arguments' placement for context and event are misplaced. Change their placement as below

'use strict';

exports.handle = (event, context, callback) => {
   callback(null, event.name);
}

answered Oct 05 '17 at 09:28

Popoi Menenet

1,018
9
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Good spot mate :). Wanted to give 10 upvote but it allow only one :) – Vijayanath Viswanathan Oct 05 '17 at 09:39

Vijayanath Viswanathan · Answer 2 · 2017-10-05T08:48:10.650

2

Even I had the same issue before and I have modified body mapping template like below. Please try it out.

#set($inputRoot = $input.path('$'))
{    
"name" : "$input.params('$.name')"
}

If you are using path parameter then please try below,

#set($inputRoot = $input.path('$'))
{
"name" : "$input.path('$.name')"
}

edited Oct 05 '17 at 08:48

answered Oct 05 '17 at 08:41

Vijayanath Viswanathan

8,027
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I still get a `null` value when using `event.name` in my callback function. – Dan Oct 05 '17 at 08:47
Are you using path parameter or query string? – Vijayanath Viswanathan Oct 05 '17 at 08:47
I am trying to access the variable from a query string so /beta/user?name=Dan - I would like to access `name` – Dan Oct 05 '17 at 08:47
Can you please write a log for 'event' in Lambda? Just to see the data – Vijayanath Viswanathan Oct 05 '17 at 08:49
I am not 100% sure what that means, I'm very new to AWS! If I use `callback(event)` then I get this response - https://qwjkvridyc.execute-api.eu-west-1.amazonaws.com/beta/user?name=foo – Dan Oct 05 '17 at 08:50
try callback(null,event) instead of callback(event) and share me result – Vijayanath Viswanathan Oct 05 '17 at 08:55
I've added that in, the result remains the same. – Dan Oct 05 '17 at 08:56
After you modified the change I suggested did you deploy the API? – Vijayanath Viswanathan Oct 05 '17 at 08:58
Yeah everything deployed, it's really bizarre! I didn't have any problems yesterday with such code. I am using Apex to push my Lambda functions, not sure if this has anything to do with it – Dan Oct 05 '17 at 09:01
Strange. Just to make sure is this because of current setup issue can you please make a sample API gateway and Lambda with the settings I have shared? – Vijayanath Viswanathan Oct 05 '17 at 09:05
Thank you very much for all of your help - The ordering of the params were wrong. – Dan Oct 05 '17 at 09:31

Can't read query parameter in AWS

2 Answers2