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
   }

M. Boyes · Accepted Answer · 2021-01-17 04:17:07Z

7

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

edited Jan 17, 2021 at 4:17

M. Boyes

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answered Jul 16, 2020 at 17:05

Bryce S

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1 Comment

D3vRandom Over a year ago

When I use post I always get this error. "SyntaxError: JSON.parse: bad escaped character at line 1 column 74 of the JSON data"

D3vRandom · Accepted Answer · 2020-07-16 21:34:22Z

SOLVED:

I found that posting directly to the AWS Lambda wasn't working because of the string format. The AWS Lambda requires JSON format with use of JSON.stringify().

        <form onsubmit="submitData();return false;">
            <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>

            function submitData() {
                var user = document.getElementById("Username").value
                var pass = document.getElementById("Password").value
                var json = { Username: user, Password: pass };
                $.ajax({
                    type: "POST",
                    url: "https://fake.execute-api.us-east-1.amazonaws.com/Prod/RegisterUser",
                    data: JSON.stringify(json),
                    beforeSend: function() { 
                        console.log("Before");
                        $("#submit").attr('disabled', true);
                    },
                    success: function(response){ 
                        console.log(response);
                        $("#submit").attr('disabled', false);
                    }
                });
            }

import pymysql
import json

def lambda_handler(event, context):
   resp = event
   return {
      "Username:": resp["Username"],
      "Password": resp["Password"]
   }

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