GraphQL has become increasingly popular as an efficient alternative to RESTful APIs for client-server interaction. This guide serves as an introductory resource to understanding GraphQL, its benefits, and how to use it in your applications. For in-depth understanding and access to a plethora of resources on this topic, visit the official GraphQL website.
GraphQL is a query language for APIs and a runtime for executing those queries which was developed by Facebook in 2012 and later open-sourced. The main advantage of using GraphQL is that it allows clients to define the exact data they need, potentially reducing the amount of data that needs to be transferred over the network.
A GraphQL Schema describes the functionality available to the clients which connect to it. It includes object types and their fields. Object types have a name and a set of fields related to the type.
Example:
type Book {
id: ID!
title: String!
author: String!
}
GraphQL Queries allow clients to request specific data and allow them to receive exactly what they need. In a query, you specify the type of the data you're trying to fetch.
Example:
{
book(id: 3) {
id
title
author
}
}
This query fetches book with id 3 and returns id, title, and author.
While queries allow for data retrieval, mutations change data in the back-end. It allows clients to create, update, and delete data.
Example:
mutation{
addBook(id:4, title:"New Book", author:"John Doe"){
id
title
author
}
}
This mutation creates a new book.
Resolvers in GraphQL provide instructions for turning a GraphQL operation into data. They resolve the query to the actual data from the database.
Example:
const resolvers = {
Query: {
book: (_, {id}) => find(books, { id: id } )
},
Mutation: {
addBook: (_, {id, title, author}) => ...
}
}
This resolver returns a book for a given id and creates new book entries.
There are many libraries available to use GraphQL with JavaScript, such as Apollo and Relay. To setup a basic GraphQL server with Apollo, you can follow the following steps:
Example:
const { ApolloServer, gql } = require('apollo-server');
const typeDefs = gql`
type Book {
title: String
author: String
}
type Query {
books: [Book]
}
`
const books = [
{
title: 'Harry Potter and the Chamber of Secrets',
author: 'J.K. Rowling',
},
{
title: 'Jurassic Park',
author: 'Michael Crichton',
},
];
const resolvers = {
Query: {
books: () => books,
},
};
const server = new ApolloServer({ typeDefs, resolvers });
server.listen().then(({ url }) => {
console.log(`🚀 Server ready at ${url}`);
});
Save this in a file, run npm install apollo-server and run the script with Node.js.
Q: Is GraphQL a database technology?
A: No, GraphQL is not a database technology. It is a query language for APIs - it's the front-end that defines the queries, and the back-end that implements the GraphQL service to run them.
Q: What language is GraphQL written in?
A: GraphQL is not tied to any specific language. Libraries are available in many languages, including JavaScript, Python, Ruby, Scala, .NET, and more.
Q: Is GraphQL only for React/Apollo/Relay?
A: No, GraphQL can be used with any library or framework, not just React or Apollo/Relay. It's also possible to execute GraphQL operations directly over HTTP without using a library.
Q: How do I start with GraphQL?
A: A good way to start learning GraphQL is to follow the official GraphQL tutorial on their site. From there you can explore other resources based on your specific needs and interests.
Q: Is GraphQL an open source project?
A: Yes, GraphQL was developed by Facebook in 2012 and open-sourced in 2015. You can find the project on GitHub.