Writing a REST API with Hapi.js

Coming from a Python background, there were a couple of different solutions for web frameworks. Some were more of the “batteries included” persuasion, while others were extremely light weight and required you to piece together different libraries. Naturally there are two camps in this situation, those who trust in the monolithic frameworks to do all the heavy lifting and those who do not and want to include only small pieces that they choose.

But, I digress. Let’s take a look at one of, in my opinion, the latter frameworks - which is hapi. hapi is an open source project written by the super smart folks over at Walmart that defines it self as:

“hapi enables developers to focus on writing reusable application logic instead of spending time building infrastructure.”

Today we are going to build a simple blog REST API using the hapi framework and some other various libraries as well. The source for this demo can be found here.

Our package.json will look something like this:

{
  "name": "hapi-rest-demo",
  "version": "0.0.0",
  "description": "A simple REST API demo using hapi",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "repository": {
    "type": "git",
    "url": "git@github.com:niix/hapi-rest-demo.git"
  },
  "author": "Nick Justice",
  "license": "MIT",
  "dependencies": {
    "hapi": "^8.1.0",
    "joi": "^5.1.0",
    "sequelize": "^2.0.0-rc7",
    "sqlite3": "^3.0.4"
  },
  "devDependencies": {
    "gulp": "^3.8.10",
    "gulp-nodemon": "^1.0.5",
    "sequelize-cli": "^1.0.3"
  }
}

Create this file in an empty directory and run npm install. This will install some various dependencies that we will be using throughout the demo. Which are hapi (of course), joi for vaildation, Sequelize a Node ORM and sqlite3 as a database to use with Sequelize for development purposes.


If you’re not familiar with ORMs or Sequelize, I highly recommend checking out their website for more info. In short, Sequelize allows you to write the same syntax for your database code but plug-and-play various SQL databases (MySQL, PostgreSQL, etc.)


Okay, now that we have our dependencies installed lets create our server file index.js

var Hapi = require('hapi');

// create the server
var server = new Hapi.Server();
server.connection({ port : 3000 })

server.route({
  method: 'GET',
  path: '/api',
  handler: function(request, reply) {
    reply({ 'api' : 'hello!' });
  }
});

server.start(function() {
  console.log('Running on 3000');
});

Go ahead and create your index.js file and run it by typing node index.js. If you visit http://localhost:3000/api in your web browser you should be presented with a simple object displaying:

{
  api: "hello!"
}

What we have done is created an extremely simple hapi server with a basic route. Routes in hapi are created by passing objects into the route method. In their most simple form these objects contain an HTTP method (GET, PUT, POST, DELETE), a path for your route and then the handler for what you want the route to respond with. Route handlers can respond with templates as well, but that is out of scope of this demo since we are writing an API.

So we don’t have to keep restarting our server when we make changes, lets create a Gulpfile that uses nodemon to monitor our files and restart the server for us automatically.

Create your Gulpfile.js with the following setup:

var gulp = require('gulp');
var nodemon = require('gulp-nodemon');

gulp.task('default', function() {
  nodemon({ script : './index.js', ext : 'js' });
});

This may be a bit overkill for such a simple demo, but as your API extends you can add various Gulp tasks to your project including linting, minification, etc.

Now to run your project you can simply type gulp and Gulp will run the server and monitor any JavaScript files that we change.


Alright lets get down to business.

Sequelize’s command line interface will create some basic boilerplate code for us and get us quickly running. The next step is to initialize Sequelize and you can do so by typing the following in our project directory:

node_modules/.bin/sequelize init

You should notice that this has created a couple of directories for us. The models directory which has a index.js file inside, the config directory that contains a basic config.json and an empty migrations directory. For more info on the boilerplate index.js, I again recommend checking out Sequelize’s website.

Now that we have Sequelize initialized, type the following to create our Post model for our blog API.

node_modules/.bin/sequelize model:create --name Post --attributes title:string,body:string

Next to the models/index.js file Sequelize has created a post.js file for us and should look like the following:

"use strict";
module.exports = function(sequelize, DataTypes) {
  var Post = sequelize.define("Post", {
    title: DataTypes.STRING,
    body: DataTypes.STRING
  }, {
    classMethods: {
      associate: function(models) {
        // associations can be defined here
      }
    }
  });
  return Post;
};

This file defines a Post model that has two fields: title and body. Both of which are strings. Next we are going to create our User model, by typing:

node_modules/.bin/sequelize model:create --name User --attributes username:string.

Similar to the previous command, this creates a User model for us which a field of username that is a String. Let’s add a relationship between the two models. In the user.js file there is a classMethods object which has an auto-generated associate method, within that method we will insert our relationship to Post:

"use strict";
module.exports = function(sequelize, DataTypes) {
  var User = sequelize.define("User", {
    username: DataTypes.STRING
  }, {
    classMethods: {
      associate: function(models) {
        // create one to many relationship
        User.hasMany(models.Post);
      }
    }
  });
  return User;
};

This creates a one to many relationship, meaning a single User has many Post.

Lets take a look at the config.json file. At this point Sequelize has created some various boilerplate code for different environments. We are going to replace the development environment object with the following, to setup our sqlite3 development database:

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

Now that all of our models are setup, we need to synchronize them. Thankfully sequelize gives us a simple way to do so, lets update our index.js and wrap the server.start code with the sequelize sync promise:

var Hapi = require('hapi');
var models = require('./models');

// create the server
var server = new Hapi.Server();
server.connection({ port : 3000 })

server.route({
  method: 'GET',
  path: '/api',
  handler: function(request, reply) {
    reply({ 'api' : 'hello!' });
  }
});

models.sequelize.sync().then(function() {
  server.start(function() {
    console.log('Running on 3000');
  });
});

Note we are including the models directory at the top of the file now. If we stop and start our server, you will see Sequelize consoling out some info about executing some SQL code. This is creating our models, if they don’t exist.

Let start our simple API. I’m big on organization, so first lets make a lib directory and create two files within that directory called api.js and routes.js.

In our api.js, lets create an endpoint that returns an array of all users.

// lib/api.js

var models = require('../models');

exports.users = {
  all: function(request, reply) {
    models.User.findAll()
      .then(function(users) {
        reply(users).code(200);
      });
  }
};

And lets add a route for this in our routes.js:

// lib/routes.js

var api = require('./api');

module.exports = [
  {
    method: 'GET',
    path: '/api/users',
    handler: api.users.all
  }
];

In addition, we want to update our index.js to pull in these new routes to the following:

var Hapi = require('hapi');
var models = require('./models');

// create the server
var server = new Hapi.Server();
server.connection({ port : 3000 })

// routes
server.route(require('./lib/routes'));

models.sequelize.sync().then(function() {
  server.start(function() {
    console.log('Running on 3000');
  });
});

By visiting http://localhost:3000/api/users we should now see that an empty array of users are being returned (because we don’t have any yet!).

This is part one of a multiple part blog post. At this point we have created a GET method to return an array of users. In our next tutorial we will be moving on to creating a POST method to input users into our database.

 
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