Building a REST API Gateway with path and query string parameters

Lab 89

Services Covered

Amazon API Gateway
Lambda

Lab description

This lab practice’s on creating an API Gateway with path and query string parameters that will be integrated with Lambda function

Create a Lambda Function
Create API Gateway
Create resources for API
Send API calls and use parameter strings

Lab date

03-10-2021

Prerequisites

AWS account

Lab steps

Create a Lambda Function. Choose Python as runtime language, create a new execution role using the policy template: Basic Lambda@Edge permissions. The function code:

import json

def lambda_handler(event, context):

   #Path parameter passed to Lambda function

   servername = event["params"]["path"]["servername"]

   #Query string parameter passed to Lambda function

   Email_id = event['params']['querystring']['emailid']

   return {

       "Path Parameter" : servername,

       "Query string Parameter" : Email_id

   }

Create a REST API Gateway. Then under Actions choose Create Resource, give it a name and type that name as Resource Path then click on Create Resource
Next create a Method in Actions and in drop down menu choose GET. As Integration type choose Lambda Function and then type the earlier created functions name. After that you’ll be presented with the API structure.
On the same screen choose Method Request and in the settings change the Request Validator field to Validate body, query string parameters and headers. Then under URL Query String Parameters add query string, enter emailid and make it Required.

Go back to Method Execution by cklicking the link on the top.
Go to the Integration Request and under Mapping templates for the Request body passthrough choose When there are no templates defined and Add mapping template with value application/json. Then generate template Method Request passthrough:
Go back and deploy the API. Select the GET method resource and in Actions choose Deploy API. Give it a name and deploy. You’ll see the Invoke URL. Then under Stages choose the name resource and GET method and copy the URL. Now if you replace name with Production and add emailid you will receive GET request’s response from the API:

Lab files

lambda.py

Acknowledgements

whizlabs

Building a REST API Gateway with path and query string parameters – Lab 89