Question 277949 in Amazon Web Sevices Question posted in
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Amazon web services – React TS – How do I add "event JSON" to a AWS Lambda GET request?

I’ve got a Lambda set up through API Gateway. The Lambda takes a value SeriesId from the event JSON and uses it. Here’s the Lambda code:

import json
import boto3
from boto3.dynamodb.conditions import Key

dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('TV-App-Seasons')

def lambda_handler(event, context):
    seriesId = int(event["SeriesId"])
    response = table.query(KeyConditionExpression=Key("SeriesId").eq(seriesId))
    data = response['Items']
            
    return {
        'statusCode': 200,
        'body': data
    }

My test event works with the following event JSON:

{
  "SeriesId": 0
}

However, how do I add this to my request from React? Since it’s a GET request I can’t add a body. I tried pathparameters in Postman, which works perfectly fine; URL/Seasons?SeriesId=0. However, when I try this in React I get a KeyError! React code:

 function getSeasons(seriesId: number) {
    const response = fetch("https://3jhuxsa1y2.execute-api.ap-northeast-1.amazonaws.com/dev/Seasons?SeriesId=" + seriesId, {
      method: "GET",
      headers: {
        'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8'
      }
    })
      .then([...]);
  }

KeyError:

  {
    errorMessage: "'SeriesId'", 
    errorType: 'KeyError', 
    requestId: '1a71a2d3-8c37-475d-8672-2958e3c84ca1',
    stackTrace: Array(1)
  }

I’ve triple checked the URL, so it has to be something else. Based on this SO post I tried swapping seriesId = int(event["SeriesId"]) with seriesId = int(event["pathparameters"]["SeriesId"]), but to no avail. Still a KeyError (and now my test fails as well!)

I’m really baffled that this works through Postman / in browser but not through React. I’ve got another Lambda which doesn’t use a event JSON which I can access with both Postman and React, so I don’t think it’s my React code. Also, CORS is enabled. Does anyone see something amiss / knows how to solve this problem? Thanks in advance!

Tags:

2

Answers


  1. 0

    Your test event should fallow API Gateway event format which is vastly different from what you use now. To have detailed view on the event, just add print(event) to your function and check exactly what the event looks like, and then adjust the test event accordingly.

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  2. 0

    However, how do I add this to my request from React? Since it’s a GET request I can’t add a body.

    You have two options:

    1. Set up a Proxy Integration with Gateway. A proxy integration will convert your GET request to a Gateway event, which will have everything the HTTP request had: the URL, complete with the parameters, the HTTP method, the headers, etc.

    2. Set up a Custom Integration with a mapping template. The template (a piece of code in Apache VTL) will transform a parameter or a fragment of path from your GET request to a simple JSON, which will be passed to your Lambda.

    It looks like you’ve set up either a proxy integration or a custom integration without a mapping template.

    In both these cases, the variable event will not have the key SeriesId.

    With the proxy integration, it will have the key queryStringParameters, which will contain a dictionary with all your query parameters.

    With a custom integration without a template, it will have some flavor of an empty value (None, or an empty string, or maybe an empty dictionary, I don’t remember which).

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