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    0.1.5 • Public • Published


    Lambda Express

    NPM version

    AWS Lambda function to integrate with Express from AWS API Gateway


    Install with npm install --save lambda-express

    Express Integration

    var lambdaExpress = require('lambda-express');
    var express       = require('express');
    var app           = express();
    // ... initialize the app as usual ...
    // create a handler function that maps lambda inputs to express
    exports.handler = lambdaExpress.appHandler(app);
    // or, if you want to do some preprocessing before delegating, pass a function in:
    exports.handler = lambdaExpress.appHandler(function(event,context) {
        // ... do some cool stuff here ...
        return app;

    API Gateway Integration

    The request expects the following attributes in the event:

        event['queryString'] = 'name=value&foo=bar';        // query string from URL
        event['headers']     = '{key1=val1, key2=val2}';    // string with header values from API Gateway
        event['user-agent']  = '...';                       // string with user agent
        event['source-ip']   = '...';                       // string with source ip for request
        event['api-id']      = '...';                       // id of the api in API Gateway
        event['pathParams']  = '{key1=val1, key2=val2}';    // list of path param values
        event['http-method'] = '...';                       // http request method
        event['resource-path'] = '...';                     // the path for the API Gateway path

    In API Gateway, this is accomplished with the following integration request mapping template:

      "stage": "$context.stage",
      "request-id": "$context.requestId",
      "api-id": "$context.apiId",
      "resource-path": "$context.resourcePath",
      "resource-id": "$context.resourceId",
      "http-method": "$context.httpMethod",
      "source-ip": "$context.identity.sourceIp",
      "user-agent": "$context.identity.userAgent",
      "account-id": "$context.identity.accountId",
      "api-key": "$context.identity.apiKey",
      "caller": "$context.identity.caller",
      "user": "$context.identity.user",
      "user-arn": "$context.identity.userArn",
      "queryString": "$input.params().querystring",
      "headers": "$input.params().header",
      "pathParams": "$input.params().path",
      "allParams": "$input.params()"

    On success, the following data structure is returned to Lambda:

        contentType: '',    // string with Content-Type header from express response
        payload:     ''     // base64 encoded string of the output from express response

    In API Gateway, this is handled with an integration response mapping template of:

    $util.base64Decode( $input.path('$.payload') )

    And a header mapping for Content-Type of integration.response.body.contentType

    If you want more headers on the return request, then add a responseHeaders key to the integration request mapping, separating headers by a :. For example:

      "pathParams": "$input.params().path",
      "allParams": "$input.params()",
      "responseHeaders": "Set-Cookie:X-Custom-Header"

    Remember, don't forget the ,. Then do the same as you did for Content-Type in the header mapping, e.g. integration.response.body.Set-Cookie.




    npm i lambda-express

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