การสร้างเซิร์ฟเวอร์ GraphQL ด้วย Apollo

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.

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!

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.

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.

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.

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.

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.

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.

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
  }
}

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?

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!