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Node.js Backend Development Bootcamp · レッスン

ApolloによるGraphQLサーバーの構築

Apollo Serverを使ってNode.jsにGraphQL APIを実装し、データソースに接続してリゾルバーを定義します。

「ApolloによるGraphQLサーバーの構築」はCoddyKit上の無料Node.js Backend Development Bootcampレッスンです。 これはレッスン3/4です。 下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。 これはNode.js Backend Development Bootcamp学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Node.js Backend Development Bootcampコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

Meet Apollo Server

Welcome to building a GraphQL server! We'll use Apollo Server, a popular open-source library that helps you implement a production-ready GraphQL API in Node.js.

  • It's easy to set up.
  • It integrates with many Node.js frameworks like Express.
  • It provides powerful tools like GraphQL Playground for testing.

Apollo Server handles the heavy lifting, letting you focus on your data.

ApolloによるGraphQLサーバーの構築 — イラスト1

Project Setup for Apollo

Let's get started by setting up our project. Open your terminal and run these commands to create a new Node.js project and install the required libraries:

  • apollo-server: The core library for building our GraphQL server.
  • graphql: The JavaScript implementation of the GraphQL specification.

Here's how to do it:

mkdir my-graphql-api
cd my-graphql-api
npm init -y
npm install apollo-server graphql

Once installed, you're ready to write some code!

Schema & Resolvers: The Core

A GraphQL server has two main parts:

  • Schema (Type Definitions): This defines the shape of your data and the operations clients can perform (queries, mutations). Think of it as the contract between client and server.
  • Resolvers: These are functions that tell GraphQL how to fetch the data for each type and field defined in your schema. They are the "backend logic" for your API.

Together, they define your API's capabilities and how it interacts with your data.

Crafting Your GraphQL Schema

We define the schema using a special template literal tag called gql (from apollo-server). This allows us to write GraphQL Schema Definition Language (SDL).

The most important type is Query, which defines all the ways clients can read data from your API. Let's define a simple Query that returns a "hello" message.

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

const typeDefs = gql`
  type Query {
    hello: String
  }
`;

console.log('Your schema is ready!');

Building Your Resolvers

Now that we have our schema, we need to tell GraphQL how to actually get the data for the hello field. This is where resolvers come in.

Resolvers are functions that match the fields in your schema. When a client queries hello, the corresponding resolver function will be executed.

const resolvers = {
  Query: {
    hello: () => 'Hello from your GraphQL API!',
  },
};

console.log('Resolvers are defined!');

Launching Your First Server

Let's put it all together! We'll combine the typeDefs and resolvers with ApolloServer to create a complete, runnable GraphQL server.

Create a file named index.js and add the following code. Then, run it with node index.js.

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

// 1. Define your schema (type definitions)
const typeDefs = gql`
  type Query {
    hello: String
  }
`;

// 2. Define your resolvers (how to fetch data)
const resolvers = {
  Query: {
    hello: () => 'Hello from your GraphQL API!',
  },
};

// 3. Create an Apollo Server instance
const server = new ApolloServer({ typeDefs, resolvers });

// 4. Start the server
server.listen({ port: 4000 }).then(({ url }) => {
  console.log(`🚀 Server ready at ${url}`);
  console.log('Try opening your browser to test it!');
});

Defining Custom Data Types

A simple "hello" isn't very exciting. Let's define a custom type, like Book, with its own fields. This shows how you structure more complex data.

Update your typeDefs to include the Book type and a books query that returns a list of them.

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

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

  type Query {
    hello: String
    books: [Book]
  }
`;

console.log('Schema updated with Book type!');

Resolving Custom Types

To make the books query work, we need to update our resolvers. For now, we'll use an in-memory array of objects to simulate a database. In real applications, resolvers connect to databases or other APIs.

Let's update the resolvers to provide data for our books query.

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

const resolvers = {
  Query: {
    hello: () => 'Hello from your GraphQL API!',
    books: () => books,
  },
};

console.log('Resolvers updated for books!');

Full API with Books

Here's the complete index.js file with our new Book type and its resolver. Run this with node index.js.

Once running, open the URL in your browser (e.g., http://localhost:4000). You'll see the GraphQL Playground, where you can test queries like:

query {
  books {
    title
    author
  }
}

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

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

  type Query {
    hello: String
    books: [Book]
  }
`;

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

const resolvers = {
  Query: {
    hello: () => 'Hello from your GraphQL API!',
    books: () => books,
  },
};

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

server.listen({ port: 4000 }).then(({ url }) => {
  console.log(`🚀 Server ready at ${url}`);
  console.log('Explore your API in GraphQL Playground!');
});

Schema vs. Resolvers Check

You've learned about the two fundamental parts of a GraphQL server: the schema (type definitions) and the resolvers.

Which of the following best describes the primary role of GraphQL Resolvers in an Apollo Server?

Apollo Server: Quick Recap

Great job! You've successfully built your first GraphQL server with Apollo Server.

  • We installed apollo-server and graphql.
  • We defined our API's structure using Type Definitions (typeDefs) written in GraphQL SDL.
  • We implemented Resolvers to specify how to fetch data for the fields in our schema, using mock data.
  • We launched our server using ApolloServer and explored it with GraphQL Playground.

This is the foundation for building powerful and flexible GraphQL APIs. Next, you can explore mutations, arguments, and connecting to real databases!

よくある質問

「ApolloによるGraphQLサーバーの構築」レッスンは無料ですか？

はい。「ApolloによるGraphQLサーバーの構築」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Node.js Backend Development Bootcampコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Node.js Backend Development Bootcampコースには全4レッスンが含まれています。

「ApolloによるGraphQLサーバーの構築」で何を学びますか？

Apollo Serverを使ってNode.jsにGraphQL APIを実装し、データソースに接続してリゾルバーを定義します。 ブラウザで直接実行するハンズオンコードでNode.js Backend Development Bootcampを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Node.js Backend Development Bootcampを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのNode.js Backend Development Bootcampは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。 これはレッスン3/4です。

「ApolloによるGraphQLサーバーの構築」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このNode.js Backend Development Bootcampレッスンでコードを書いて実行できますか？

はい。すべてのNode.js Backend Development Bootcampレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

このコースのすべてのレッスン

  1. Node.jsによるサーバーレス入門
  2. GraphQL API設計の原則
  3. ApolloによるGraphQLサーバーの構築
  4. リアルタイムデータ向けGraphQLサブスクリプション
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