Building a GraphQL API with Apollo Server

When it comes to designing robust and flexible APIs, many developers turn to GraphQL as a compelling alternative to traditional REST architectures. By allowing clients to request specific data in a declarative way, GraphQL provides a level of query optimization and customization that RESTful APIs can't match.

But how can we easily set up and maintain a scalable GraphQL API that satisfies our evolving development needs? One highly-recommended tool in this area is Apollo Server – an incredibly versatile implementation that delivers optimal developer productivity with effective operation out of the box.

Let's dive deeper into the world of GraphQL and explore how we can use Apollo Server to build a custom GraphQL API.

Understanding GraphQL In-Memory Data Store in Apollo

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Getting Started with Apollo Server

To build a custom GraphQL server, we will use Apollo Server as our primary server framework since it comes with support for modern features and technologies as outlined by the standard official latest available specifications in the GraphQL world.

Let's start by creating a new Node.js project and installing the required dependencies:

npm init -y
npm install apollo-server graphql

Next, we'll create a new file called server.js and add the following code to get started with Apollo Server:

const { ApolloServer } = require('apollo-server');
const typeDefs = require('./schema');
const resolvers = require('./resolvers');

const server = new ApolloServer({
  typeDefs,
  resolvers,
});

server.listen().then(({ url }) => {
  console.log(`Server listening on ${url}`);
});

In this example, we're importing the ApolloServer class from the apollo-server package and creating a new instance of it. We're also importing our schema and resolvers from separate files.

Defining Our Schema

Our schema defines the structure of our GraphQL API, including the types of data that can be queried and the operations that can be performed on that data.

Let's create a new file called schema.js and add the following code to define our schema:

const { gql } = require('apollo-server');

const typeDefs = gql`
  type Book {
    title: String
    author: String
  }

  type Query {
    books: [Book]
  }
`;

module.exports = typeDefs;

In this example, we're defining a Book type with two fields: title and author. We're also defining a Query type with a single field called books that returns an array of Book objects.

Defining Our Resolvers

Our resolvers define how our schema is implemented, including the logic for querying and mutating data.

Let's create a new file called resolvers.js and add the following code to define our resolvers:

const books = [
  { title: 'The Great Gatsby', author: 'F. Scott Fitzgerald' },
  { title: 'To Kill a Mockingbird', author: 'Harper Lee' },
];

const resolvers = {
  Query: {
    books: () => books,
  },
};

module.exports = resolvers;

In this example, we're defining a Query resolver that returns an array of Book objects.

Running Our Server

Now that we've defined our schema and resolvers, we can run our server and start querying our API.

Let's add the following code to our server.js file to run our server:

server.listen().then(({ url }) => {
  console.log(`Server listening on ${url}`);
});

We can now start our server by running the following command in our terminal:

node server.js

This will start our server and make it available at http://localhost:4000. We can now use a tool like GraphQL Playground to query our API and explore our schema.

Conclusion

In this article, we've learned how to use Apollo Server to build a custom GraphQL API. We've defined our schema and resolvers, and we've run our server to make our API available for querying.

Apollo Server is a powerful tool for building scalable and flexible GraphQL APIs. With its support for modern features and technologies, it's an ideal choice for building robust and maintainable APIs.

I hope this article has been helpful in getting you started with Apollo Server. Happy coding!