Serverless GraphQL — AWS AppSync, Lambda, Spring Boot

Serverless GraphQL - AWS AppSync, Lambda, Spring Boot

Introduction

In this & this article, we have seen how we can implement the standalone AWS Lambda function and its integration via AWS API Gateway. In case you have not gone through those previous articles then I would strongly recommend going through those articles first.

If you are not familiar with GraphQL concepts then I would request going through this & this article.

Leveraging our learning from the past, we will learn how we can create GraphQL API using the AWS AppSync service.

Tools/Frameworks

IDE  — IntelliJ Idea/Eclipse

Language  — Java 8 or above

Framework  — Spring boot

Build Tool  — Maven

Cloud Provider  — AWS

AWS Services  — AppSync & Lambda

Goal

OK, so let's discuss now what we are trying to achieve. Please refer to the high-level design below.

We will create AppSync GraphQL API which will invoke the lambda function backed by the spring boot cloud function & return a response.

High Level Design — AWS AppSync/Lambda

Sample Application

Let's assume that we have a sample application (don’t worry! you can refer to the git repository at the end of this article) deployed as a part of the AWS lambda function. Here is the “User” model

→ Model

public class User {

    private String name;
    private Integer id;
}

→ Functional API

We will use the “getAllUsers” function to be called as a part of lambda which will return the List

With this basic implementation, let's go ahead & create AppSync GraphQL API.

Create — AWS AppSync GraphQL API

As we have the application background ready, let's jump on how to create/configure AWS AppSync GraphQL API.

→ Log in to the AWS management console. Search & navigate to the AppSync service.

→ Click on the “Create API” button & choose the “Build from scratch” option.

→ Next, let's give our API the name “UserAppSyncApp” & click on create that will create AWS AppSync GraphQL API.

Configure

Now, let's concentrate on the configuration part.

→ Let’s navigate to the API which we have created & configure types/schema based on the model for which we want to perform GraphQL query/mutation operation. Here, we can see that the “User” type is in line with the model of the lambda function.

AWS AppSync — Schema

type Mutation {
    addUser(id: ID!, name: String): User!
}

type Query {
    getUser(id: ID!): User
    getAllUsers: [User]
}

type User {
    id: ID!
    name: String
}

schema {
    query: Query
    mutation: Mutation
}

You might think that schema is created then it should start working, right? But, actually no, it will not work. why? because we have not integrated our lambda function as a data source to our AppSync API.

So, now let's configure the AWS Lambda function as a data source for our newly created “UserAppSyncApp” AppSync API.

→ Navigate to the data source & let’s attache our lambda function.

1. Data source name — Enter any meaningful name for the data source
2. Data source type — Choose “AWS Lambda function”
3. Region — Choose the region to which the lambda function belongs.
4. Function ARN — Choose the function which you want to bind to the AppSync API
5. Create or use an existing role — Use the appropriate existing role if you have already one else create a new one.

AWS AppSync — Data Source Configuration

Testing

As we have almost all configurations in place, let’s verify.

→ Navigate to the “Queries” section where you can see all the queries which we have configurated as a part of schema configuration. Click on the play button.

AWS AppSync — Queries

→ Let's see the result.

AWS AppSync — Testing

Yey, we have successfully implemented AWS AppSync GraphQL API using AWS Lambda as a data source.

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Git Repository

https://github.com/shethapurv/aws/tree/main/awslambda-appsync-example

References

https://docs.aws.amazon.com/appsync/latest/devguide/what-is-appsync.html

Schemas and Types