Extracting Parameters from POST Request in Python Lambda

Question

Context: I'm trying to make a POST request to a AWS lambda function written in python from JavaScript. I will then enter the information in the POST request into a Database.

Problem: I can't seem to figure out how to get the information out of the POST request. and store it into variables.

I've tried to use the event['Username'] which in the testing simulation provided by AWS works although in practice doesn't.

<form method="POST" action="https://fake.execute-api.us-east-1.amazonaws.com/Prod/RegisterUser">
            <label for="Username">Username:</label><br>
            <input type="text" id="Username" name="Username" value=""><br>
            <label for="password">Password:</label><br>
            <input type="text" id="Password" name="Password" value=""><br><br>
            <input type="submit" id="submit" value="Submit" >
    </form> 

POST /Prod/RegisterUser HTTP/1.1
Host: fake.execute-api.us-east-1.amazonaws.com
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 24
Connection: close
Upgrade-Insecure-Requests: 1

Username=jat&Password=sa

import pymysql
import json

#endpoint = 'fake.us-east-1.rds.amazonaws.com'
#username = 'admin'
#password = 'admin'
#database_name = 'fake'

#connection
#connection = pymysql.connect(endpoint, user=username, passwd=password, db=database_name)

def lambda_handler(event, context):

   user =  event['Username']
   password = event['Password']
   
   return {
      "Username": user,
      "Password":password
   }

Answer 1

Your HTTP body will come through lambda as event['body'].

Also, I think you'll need to parse the JSON string of the body, using json.loads.

Lastly, I saw your HTML is doing a GET method, you might want to fix that:

<form method="POST" action="https://fake.execute-api.us-east-1.amazonaws.com/Prod/RegisterUser">

Serverless is a great resource for lambda functions. Here's an example of theirs that might apply to your case:

https://github.com/serverless/examples/blob/master/aws-python-rest-api-with-dynamodb/todos/create.py