CODEWITHSUNDEEP
typescriptaws-cdk
Stoyan Georgiev
Stoyan Georgiev

Reputation: 305

How to configure sending(apigateway) and getting(lambda) request Query Parameters with CDK for Typescript

I've cdk initialized an app. My app has a stack of ApiGateway with a 'GET' method bound to the root ('/'). A Lambda function is bound to the 'GET' method. I want when I send a 'GET' request with query parameters e.g. ?param1=uno&param2=dos to access them inside myHandler with something like 

!pseudo-code alert! 
const queryParams = event.queryParams

Stack config in lib/my-app-stack.ts

import cdk = require("@aws-cdk/core");
import lambda = require("@aws-cdk/aws-lambda");
import apigateway = require("@aws-cdk/aws-apigateway");
import path = require("path");

export class ApiIntegrationStack extends cdk.Stack {
  constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    // Handlers
    const my_handler = new lambda.Function(this, "myHandler", {
      code: lambda.Code.asset(path.join(__dirname, "../src")),
      handler: "handler.myHandler",
      runtime: lambda.Runtime.NODEJS_8_10,
      memorySize: 1024
    });
    const my_integration = new apigateway.LambdaIntegration(
      my_handler
    );

    const default_handler = new lambda.Function(this, "defaultHandler", {
      code: lambda.Code.asset(path.join(__dirname, "../src")),
      handler: "handler.defaultHandler",
      runtime: lambda.Runtime.NODEJS_8_10,
      memorySize: 1024
    });

    // API Gateway set-up
    const my_api = new apigateway.LambdaRestApi(this, "myApi", {
      handler: default_handler,
      proxy: false
    });

    // Routing
    my_api.root.addMethod("GET", my_integration); /*, {
      requestParameters: {
        'page_tag': true,
        'language': true
      }
    });
    */
  }
}

Handler config in src/handler.ts

"use strict";
import { Handler, Context, Callback } from "aws-lambda";

const myHandler: Handler = (
  event: any,
  context: Context,
  callback: Callback
) => {

  const queryParams = []; // ??
  const response = {
    statusCode: 200,
    headers: {
      "Access-Control-Allow-Origin": "*" // Required for CORS support to work
    },
    body: JSON.stringify({
      message: "Ahoy, My handler here!"
    })
  };

  callback(null, response);
};

const defaultHandler: Handler = (
  event: any,
  context: Context,
  callback: Callback
) => {
  const response = {
    statusCode: 200,
    headers: {
      "Access-Control-Allow-Origin": "*" // Required for CORS support to work
    },
    body: JSON.stringify({
      message: "Ahoy, Default handler here!"
    })
  };

  callback(null, response);
};

export { myHandler, defaultHandler };

Questions I find related to this question:

requestParameters returning “Invalid mapping expression specified: true”

passing query params for aws lambda function

Thank you for your attention!

Upvotes: 4

Views: 5952

Answers (1)

Jon Madison
Jon Madison

Reputation: 456

Somehow this also wasn't completely clear to me from (skimming) the documentation; i think it requires some contextual knowledge of api gateway itself.

the .addMethod takes 3 parameters, one of which is requestParameters where you state that you have method request parameters, i.e.

requestParameters: {
   "method.request.querystring.page_tag": true,
   "method.request.querystring.language": true,
}

then, in the integration itself, provide a requestParameters value where you map the integration request's query string params to the method request params you set up, i.e.

     requestParameters: {
          "integration.request.querystring.page_tag":
          "method.request.querystring.page_tag", 
          "integration.request.querystring.language":
          "method.request.querystring.language",
        },
...

Upvotes: 8

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