An application programming interface (API) is a set of methods that allow us to programmatically access a component. APIs can be built for different layers, such as the web (http/rest), database, and operating system layers, and so on. A representational state transfer (REST) API is an API that uses REST principles and HTTP protocol to build web APIs that can be programmatically consumed by clients over a network, such as the internet.

Amazon API Gateway is the primary service within AWS for building serverless, scalable, and secure REST APIs. It acts as a gateway between your application and the outside world. You only pay for the API calls and data that are transferred out, and you do not have to maintain a server. It also provides support for testing, authorization, API version management, deployment, and maintaining and monitoring your REST APIs.

Amazon API...

In this recipe, we will create a simple REST API with mock integration, using CLI commands. We will specify a name as a path parameter, and the API will greet that person. In the next recipe, we will use CloudFormation templates to create the API. From that point, we will use both the CLI commands and the CloudFormation templates.

In the previous recipe, we built a simple REST API using the AWS CLI. In this recipe, we will use the CloudFormation template to create an API and understand the benefits of using CloudFormation over the AWS CLI. Most enterprise projects use CloudFormation templates for their infrastructure provisioning in AWS.

In this recipe, we will use the CloudFormation templates written in YAML. To deploy those templates, we will still use the AWS CLI. So, a basic understanding of CloudFormation, the AWS CLI, and YAML are good to have. If you are new to these, please refer to the respective Your first AWS Lambda recipe from Chapter 1, Getting Started with Serverless Computing...

In the previous two recipes in this chapter, we created an API with mock integration. We also discussed REST principles, HTTP essentials, and the AWS CLI commands and CloudFormation template components used. In this recipe, we will integrate an API gateway API with Lambda. The API is similar to the previous one (with a path parameter), but we will use an AWS integration instead of mock integration.

You need an active AWS account. You need to follow the section Getting started in the recipes Your first AWS Lambda and Your first Lambda with AWS CLI from Chapter 1, Getting Started with Serverless Computing on AWS, to set up Java, Maven, the parent project, serverless...

In this recipe, we will create a simple POST API method that has an AWS integration with Lambda. A REST client will send a JSON request body to the API method in the format required by our Lambda, which will be passed through to the Lambda. We will use the same Lambda from the previous recipe.

GET is the default HTTP method for web browser requests; hence, we could invoke GET API methods from the browser in the previous recipes. To invoke other HTTP methods or override various HTTP options, we need to use a REST client. We will use the Postman REST client, which is available as a standalone app, as well as an extension to the Chrome browser.

You need an active...

Amazon API Gateway allows us to map our incoming requests to a format that's required by our Lambda, and map the response from the Lambda into a format that's required by the client, all by using the mapping templates. The API Gateway body mapping templates are based on the Apache Velocity Template Language (VTL) and JSONPath expressions.

In this recipe, we will see how to map a JSON body coming from a request into another JSON structure, as required by the backend (Lambda). We will also map the JSON response from the backend (Lambda) into a different JSON response structure which is sent back as the response. We will use the same Lambda from the recipe Building your first API with Lambda integration, but the client will send the request in a different format.

In this recipe, we will add validation to request payloads by using models. We will define a model by using the JSON schema draft language, and we will then use it to validate our payloads. We will use the same Lambda that we used in the recipe Building your first API with Lambda integration.

You need an active AWS account. You need to follow the section Getting started in the recipes Your first AWS Lambda and Your first Lambda with AWS CLI from Chapter 1, Getting Started with Serverless Computing on AWS to set up Java, Maven, the parent project, serverless-cookbook-parent-aws-java, and AWS CLI, and may also read other notes there including code usage guidelines, S3 bucket...

In this recipe, we will configure our API to act as a proxy for a Lambda. We will create a new Lambda function that extracts the required data from the incoming request. While using proxy integration, Lambda needs to implement the low-level RequestStreamHandler that gives us access to the InputStream and OutputStream.

You need an active AWS account. You need to follow the section Getting started in the recipes Your first AWS Lambda and Your first Lambda with AWS CLI from Chapter 1, Getting Started with Serverless Computing on AWS to set up Java, Maven, the parent project, serverless-cookbook-parent-aws-java, and AWS CLI, and may also read other notes there including code...