Server middleware in GraphQL - Mini Project: Build & Apply

GraphQL Server Middleware Setup

📖 Scenario: You are building a simple GraphQL server for a bookstore. You want to add middleware to log each request's details before processing it.

🎯 Goal: Create a GraphQL server with middleware that logs the operation name and variables of each request.

📋 What You'll Learn

Create a basic GraphQL schema with a Query type that has a books field returning a list of books.

Add a middleware function that logs the operation name and variables of each incoming request.

Integrate the middleware into the GraphQL server setup.

Ensure the middleware runs before the resolver executes.

💡 Why This Matters

🌍 Real World

Middleware in GraphQL servers helps add features like logging, authentication, and validation without changing resolver logic.

💼 Career

Understanding server middleware is essential for backend developers working with GraphQL APIs to build secure and maintainable services.

1

Define the GraphQL schema

Create a GraphQL schema with a type Query that has a books field returning a list of Book objects. Define the Book type with id (ID), title (String), and author (String).

GraphQL

# Define the GraphQL schema with Query and Book types
# Your code here

Hint

Use the gql tag to define your schema. Include Book and Query types exactly as described.

2

Create a middleware function

Create a middleware function called logMiddleware that takes resolve, parent, args, context, and info as parameters. Inside, log the info.operation.operation and args to the console, then call and return resolve(parent, args, context, info).

GraphQL

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

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

  type Query {
    books: [Book!]!
  }
`;

// Create the logMiddleware function
// Your code here

Hint

Define logMiddleware as an async function with the specified parameters. Use console.log to print operation and arguments, then call resolve.

3

Add resolver with middleware

Create a resolver object with a Query field. For books, wrap the resolver function with logMiddleware. The resolver should return an array of two books with exact values: { id: '1', title: '1984', author: 'George Orwell' } and { id: '2', title: 'Brave New World', author: 'Aldous Huxley' }.

GraphQL

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

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

  type Query {
    books: [Book!]!
  }
`;

const logMiddleware = async (resolve, parent, args, context, info) => {
  console.log(`Operation: ${info.operation.operation}`);
  console.log('Arguments:', args);
  return resolve(parent, args, context, info);
};

// Create resolvers with books field wrapped by logMiddleware
// Your code here

Hint

Define resolvers with a Query object. Wrap the books resolver function with logMiddleware. Return the exact array of book objects.

4

Setup Apollo Server with middleware

Create an ApolloServer instance called server using typeDefs and resolvers. Export the server as the default export.

GraphQL

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

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

  type Query {
    books: [Book!]!
  }
`;

const logMiddleware = async (resolve, parent, args, context, info) => {
  console.log(`Operation: ${info.operation.operation}`);
  console.log('Arguments:', args);
  return resolve(parent, args, context, info);
};

const resolvers = {
  Query: {
    books: logMiddleware(async () => [
      { id: '1', title: '1984', author: 'George Orwell' },
      { id: '2', title: 'Brave New World', author: 'Aldous Huxley' }
    ])
  }
};

// Create ApolloServer instance and export it
// Your code here

Hint

Import ApolloServer from apollo-server. Create server with typeDefs and resolvers. Export it using module.exports.