Super Simple GraphQL with Node

GraphQL is a specification and therefore language agnostic. When it comes GraphQL development with node, there are various options available ranging from Celý článek

GraphQL is a specification and therefore language agnostic. When it comes GraphQL development with node, there are various options available ranging from graphql-js, express-graphql to apollo-server. In this tutorial, I'll be showing you how simple it is to get a fully featured GraphQL server up and running in Node.js with Apollo Server.

Since the lauch of Apollo Server 2, creating GraphQL server with Apollo Server has gotten a lot easier, to to mention the other features that came with it. For the purpose of demonstration, we'll be building a GraphQL server for a simple recipe app.

Prerequisites

This tutorial assumes the following:

• Node.js and NPM installed on your computer
• Basic knowledge of GraphQL

What is GraphQL?

GraphQL is a declarative data fetching specification and query language for APIs. It was created by Facebook. GraphQL is an effective alternative to REST, as it was created to overcome some of the shortcomings of REST like under/over fetching.

How does it work?

Unlike REST, GraphQL uses one endpoint. So basically, we make one request to the endpoint and we'll get one response as JSON. This JSON response can contain as little or as much data as we want. Like REST, GraphQL can be operated over HTTP, though GraphQL is protocol agnostic.

A typical GraphQL server is comprised of schema and resolvers. A schema (or GraphQL schema) contains type definitions that would make up a GraphQL API. A type definition contains field(s), each with what it is expected to return. Each field is mapped to a function on the GraphQL server called a resolver. Resolvers contains the implementation logic and returns data for a field. Other words, schema contains type definition, while resolvers contains the actual implementations.

Setting up the database

We’ll start by setting up our database. To keep things simple and straightforward, we’ll be using SQLite for our database. Also, we’ll be using Sequelize, which is an ORM for Node.js, to interact with our database. First, let's create a new project:

$ mkdir graphql-recipe-server
$ cd graphql-recipe-server
$ yarn init -y

Next, let's install Sequelize:

$ yarn add sequelize sequelize-cli sqlite3

In addtion to install Sequelize, we are also installing sqlite3 package for Node.js. To help us scaffold our project, we’ll be using the Sequelize CLI, which we are installing as well.

Let's scaffold our project with the CLI:

$ node_modules/.bin/sequelize init

This will create following folders:

config: contains config file, which tells Sequelize how to connect with our database. models: contains all models for our project, also contains an index.js file which integrates all the models together. migrations: contains all migration files. seeders: contains all seed files.

For the purpose of this tutorial, we won't be creating with any seeders. Open config/config.json and replace it content with below:

// config/config.json

{
  "development": {
    "dialect": "sqlite",
    "storage": "./database.sqlite"
  }
}

We set the dialect to sqlite and set the storage to point to a SQLite database file.

Next, we need to create the database file directly inside the project's root directory:

$ touch database.sqlite

Creating models and migrations

With the database set up out of the way, we can start creating the models for our project. Our recipe app will have two models: User and Recipe. We’ll be using the Sequelize CLI for this:

$ node_modules/.bin/sequelize model:create --name User --attributes name:string,email:string,password:string

This is will create a user.js file inside the models directory and a corresponding migration file inside the migrations directory.

Since we don't want any on the fields on the User model to be nullable, we need to explicitly defined that. Open migrations/XXXXXXXXXXXXXX-create-user.js and update the fields definitions as below:

// migrations/XXXXXXXXXXXXXX-create-user.js

name: {
    allowNull: false,
    type: Sequelize.STRING
},
email: {
    allowNull: false,
    type: Sequelize.STRING
},
password: {
    allowNull: false,
    type: Sequelize.STRING
}

Then we'll do the same in the User model:

// models/user.js

name: {
    type: DataTypes.STRING,
    allowNull: false
},
email: {
    type: DataTypes.STRING,
    allowNull: false
},
password: {
    type: DataTypes.STRING,
    allowNull: false
}

Next, let's create the Recipe model:

$ node_modules/.bin/sequelize model:create --name Recipe --attributes title:string,ingredients:text,direction:text

Just as we did with the User model, we'll do the same for the Recipe model. Open migrations/XXXXXXXXXXXXXX-create-recipe.js and update the fields definitions as below:

// migrations/XXXXXXXXXXXXXX-create-recipe.js

userId: {
    type: Sequelize.INTEGER.UNSIGNED,
    allowNull: false
},
title: {
    allowNull: false,
    type: Sequelize.STRING
},
ingredients: {
    allowNull: false,
    type: Sequelize.STRING
},
direction: {
    allowNull: false,
    type: Sequelize.STRING
},

You'll notice we have an additional field: userId, which would hold the ID of the user that created a recipe. More on this shortly.

Update the Recipe model as well:

// models/recipe.js

title: {
    type: DataTypes.STRING,
    allowNull: false
},
ingredients: {
    type: DataTypes.STRING,
    allowNull: false
},
direction: {
    type: DataTypes.STRING,
    allowNull: false
}

To wrap up with our models, let's define the relationship between them. You might have guessed with the inclusion of the userId column to the recipes table, that we want to be able to associate a recipe to a user and vice-versa. So, we want a one-to-many relationships between our models.

Open models/user.js and update the User.associate function as below:

// models/user.js

User.associate = function (models) {
    User.hasMany(models.Recipe)
}

We need to also define the inverse of the relationship on the Recipe model:

// models/recipe.js

Recipe.associate = function (models) {
    Recipe.belongsTo(models.User, { foreignKey: 'userId' })
}

By default, Sequelize will use a camel case name from the corresponding model name and its primary key as the foreign key. So in our case, it will expect the foreign key to be UserId. Since we named the column differently, we need to explicitly define the foreignKey on the association.

Now, we can run the migrations:

$ node_modules/.bin/sequelize db:migrate

Creating the GraphQL server

Phew! Let's get to the GraphQL stuff. As earlier mentioned, we'll be using Apollo Server for building our GraphQL server. So, let's install it:

$ yarn add apollo-server graphql bcryptjs

Apollo Server requires graphql as a dependency, hence the need to install it as well. Also, we install bcryptjs, which we'll use to hash users passwords later on.

With those installed, create a src directory, then within it, create an index.js file and paste the code below in it:

// src/index.js

const { ApolloServer } = require('apollo-server')
const typeDefs = require('./schema')
const resolvers = require('./resolvers')
const models = require('../models')

const server = new ApolloServer({
  typeDefs,
  resolvers,
  context: { models }
})

server
  .listen()
  .then(({ url }) => console.log('Server is running on localhost:4000'))

Here, we create a new instance of Apollo Server, passing to it our schema and resolvers (both which we'll create shortly). We also pass the models as the context to the Apollo Server. This will allow us have access to the models from our resolvers.

Finally, we start the server.

Defining the GraphQL Schema

GraphQL schema is used to define the functionality a GraphQL API would have. Basically, a GraphQL schema is comprised of types. A type can be for defining the structure of our domain specific entity. In addition to defining types for our domain specific entities, we can also define types for GraphQL operations, which will in turn translates to the functionality a GraphQL API will have. These operations are: queries, mutations and subscriptions. Queries are used to perform read operations (fetching of data) on a GraphQL server. Mutations on the other hand are used to perform write operations (inserting, updating or deleting data) on a GraphQL server. Subscriptions are completely different from these two, as they are used to add realtime functionality to a GraphQL server.

We'll be focusing only on queries and mutations in this tutorial.

Now that we understand what GraphQL schema is, let's create the schema for our app. Within the src directory, create a schema.js file and paste the code below in it:

// src/schema.js

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

const typeDefs = gql` `type User {
    id: Int!
    name: String!
    email: String!
    recipes: [Recipe!]!
  }

  type Recipe {
    id: Int!
    title: String!
    ingredients: String!
    direction: String!
    user: User!
  }

  type Query {
    user(id: Int!): User
    allRecipes: [Recipe!]!
    recipe(id: Int!): Recipe
  }

  type Mutation {
    createUser(name: String!, email: String!, password: String!): User!
    createRecipe(
      userId: Int!
      title: String!
      ingredients: String!
      direction: String!
    ): Recipe!
  }
``

module.exports = typeDefs

First, we pull in the gql package from apollo-server. Then we use it to define our schema. Ideally, we'd want to our GraphQL schema to mirror our database schema as much as possible. So we define to types: User and Recipe, which corresponds to our models. On the User type, in addition to defining the fields we have on the User model, we also define a recipes fields, which will be used to retrieve the user's recipes. Same with the Recipe type, we define a user field, which will be used to get the user of a recipe.

Next, we define three queries; for fetching a single user, for fetching all recipes that have been created and for fetching a single recipe respectively. Both the user and recipe queries can either return a user or recipe respectively or return null if no corresponding match was found for the ID. The allRecipes query will always return a array of recipes, which might be empty if no recipe as been created yet.

Lastly, we define mutations for creating and new user as well as creating a new recipe. Both mutations return back the created user and recipe respectively.

Tips: The ! denotes a field is required, while [] denotes the field will return an array of items.

Creating the resolvers

Resolvers defines how the fields in a schema is executed. In other words, our schema is useless without resolvers. Creating a resolvers.js file inside the src directory and past the following code in it:

// src/resolvers.js

const resolvers = {
    Query: {
        async user (root, { id }, { models }) {
              return models.User.findById(id)
        },
        async allRecipes (root, args, { models }) {
              return models.Recipe.findAll()
        },
        async recipe (root, { id }, { models }) {
              return models.Recipe.findById(id)
        }
      },
}

module.exports = resolvers

We start by creating the resolvers for our queries. Here, we are making use of the models to perform the necessary queries on the database and simply return the results.

Still inside src/resolvers.js, let's import bcryptjs at the top of the file:

// src/resolvers.js

const bcrypt = require('bcryptjs')

Then add the code below immediately after the Query object:

// src/resolvers.js

Mutation: {
    async createUser (root, { name, email, password }, { models }) {
        return models.User.create({
            name,
            email,
            password: await bcrypt.hash(password, 10)
          })
    },
    async createRecipe (root, { userId, title, ingredients, direction }, { models }) {
        return models.Recipe.create({ userId, title, ingredients, direction })
    }
},

The createUser mutation accepts the name, email and password of a user, and creates a new record in the database with the supplied details. We make sure to hash the password using the bcrypt package before persisting it to the database. It returns the newly created user. The createRecipe mutation accepts the ID of the user that's creating the recipe as well as the details for the recipe itself, persists them to the database and returns the newly created recipe.

To wrap up with the resolvers, let's define how we want our custom fields (recipes on the User and user on Recipe) to be resolved. Add the code below inside src/resolvers.js just immediately the Mutation object:

// src/resolvers.js

User: {
    async recipes (user) {
        return user.getRecipes()
    }
},
Recipe: {
    async user (recipe) {
        return recipe.getUser()
    }
}

These uses the methods (getRecipes() , getUser()), which are made available on our models by Sequelize due to the relationships we defined.

Testing our GraphQL server

It's time to test our GraphQL server out. First, we need to start the server with:

$ node src/index.js

This should be running on http://localhost:4000, and we should see GraphQL Playground running if we access it. Let's try creating a new recipe:

# create a new recipe

mutation {
  createRecipe(
    userId: 3
    title: "Sample 2"
    ingredients: "Salt, Pepper"
    direction: "Add salt, Add pepper"
  ) {
    id
    title
    ingredients
    direction
    user {
      id
      name
      email
    }
  }
}

We should see a result as below:

Conclusion

In this tutorial, we looked at how to creating a GraphQL server in Node.js with Apollo Server. We also saw how to integrate a database with a GraphQL server using Sequelize.