How to Write a GraphQL Schema?

Now let’s create a GraphQL Schema inside a GraphQL Server to server requests to a GraphQL API

Step 1: Creating a Node.js Server

We will create a basic node.js server, and in later steps, we will create a GraphQL API with a schema inside the server.

First, run the below command to initialise an npm project

npm init -y

Now, install the dependencies for creating an Apollo Server using the below command –

npm i apollo-server

Now, create a new file called server.js, where we will write the logic of creating a GraphQL server, and we will also add the GraphQL Schema Types in the same file. The final project structure should look like below

Step 2: Defining Schema Type

In this step, we will define the GraphQL Schema Type of the User and the Query, so when the endpoint gets hit, the end user can ask the query to return some or all of the types in the response data. In this example, we will define a user with types of just id, name, and age, to keep it simple.

Javascript

const typeDefs = gql` 
  type User { 
    id: ID! 
    name: String! 
    age: Int! 
  } 
  
  type Query { 
    getUser(id: ID!): User 
  } 
`;

Step 3: Creating a Resolver to Serve the Requests

In this step, we will create a GraphQL resolver to serve the requests that are hit to the GraphQL endpoint. Since in the above step, we defined the type for only one query `getUser`, we will create the resolver for the same. And we will just return a static user object with name “John Doe”, and age as “20”, as we are not creating a DB connection here.

Javascript

const resolvers = { 
  Query: { 
    getUser: (_, { id }) => { 
      return { id, name: 'John Doe', age: 28 }; 
    }, 
  }, 
};

Step 4: Creating and Starting the Apollo Server

In this step, we will create and start our Apollo Server on port 4000.

Javascript

const server = new ApolloServer({ typeDefs, resolvers }); 
  
server.listen().then(({ url }) => { 
  console.log(`Server running at ${url}`); 
}); 

Step 5: Integrating the Above Code Together in a Single File

In this step, we will put all the above pieces of code together into a single file, server.js, that we created in the beginning. Let’s start our server by running the below command –

node server.js

You will see the output of the server running –

Server running at http://localhost:4000/

Now, open the graphQL playground here, and execute the below query to fetch the data on the basis of provided schema

Javascript

query { 
  getUser(id: "1") { 
    id 
    name 
    age 
  } 
}

Output:

Schema in GraphQL

GraphQL is a powerful open-source Query Language for APIs. It is most commonly known for its single endpoint query which allows the user to define a single endpoint to fetch all the information needed. Schemas in GraphQL are the blueprints for its APIs and define what the request-response structure would look like. In this article, we will learn about GraphQL Schemas, and we will create some ourselves.