Basic API Creation with Node.JS

API (Application Programming interface) is a set of programming instructions and standards for accessing a web based software application.

Many software companies allow third party apps to integrate with their services. So they don’t provide direct access to their databases or business logic directly. They provide one interface from which they can easily access the database, without any efforts from scratch.

For example, now a day’s many applications allow signing up from Facebook account. Once you authenticate, with the help of the Facebook API, they collect your personal information, Friends details, or post any things. Also, many Mobile Applications are getting data from the server. For that purpose they are creating Restful service and gets result from the service.

Node.js is a good choice when we need some scalable app with lesser effort and fast development. There are many frameworks available which easily creates Controllers automatically based on Models defined. Let’s understand what is node.js?

Node.js is a software platform for scalable server-side and networking applications. Node.js application is written in JavaScript and can be run within the Node.js runtime on different platforms like windows, Mac OS X and Linux without any changes.

Node.js applications are designed to maximize throughout and efficiency of the app with the help of non-blocking I/O asynchronous events. Node.js applications run single-threaded, although Node uses multiple threads for file and network events. Node.js contains a built-in HTTP server library, and making it possible to run a web server without Apache or any server.

Many companies like PayPal, Linkedin, Yahoo, and Microsoft is using Node.js in their product development. PayPal has created their own framework called KankenJS using Node, which is used in development all their new web applications.

If Node.js is new for you, in this article we will see how to install node.js, develop and run an application with the help of Node.js.

You can download the NodeJS installer from here.

Creating an HTTP server which responds to client query is very easy to build with node.js.

Just write below code in a file and save as server.js

var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello Node.js\n');
}).listen(80, "127.0.0.1");
console.log('Server running at http://127.0.0.1:80/');

To run the server, execute a file with the node program from the command line.

var express = require('express');
var app = express();app.get('/', function(req, res){ res.send('hello world');});
app.listen(80);

var express = require('express');
var userController = require('./usercontroller.js');
var mongoose = require(' mongoose');

// Initializing express Object
var app = express();

app.configure(function () {
app.use(express.logger('dev'));
app.use(express.bodyParser());
});

// Connecting to Database
mongoose.connect(mongodb://localhost/myDb);

// Start writing Routes here.
app.get('/user', userController.getAllUsers);

app.get('/user/:id', userController.getUserById);

app.post('/user', userController.addUser);

app.put('/user/:id', userController.updateUser);

app.delete('/user/:id', userController.deleteUserById);

// Starts Listening on port 9000
app.listen(9000);
console.log ('Server listening on port : 9000');

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId;

/* By default each Schema contains _id property as a unique field*/

var userSchema = new Schema({
emailId: String,
firstName: String,
lastName: String,
password: String
});

exports.userModel = mongoose.model('User', userSchema);

Mongoose is a node module for performing and simplifying various Mongo database related operations. Mongoose is MongoDB Object modeling module for Node.js

In this file we have done the following things:

• Defining Schema for the User with email, password, first name and last name field.
• Creating Model from the Schema.

var UserModel = require('./model.js').userModel;

// No User Inputs required.
exports.getAllUsers = function(req, res) {

var responseObj = new Object();
responseObj.result = false;

UserModel.find(function(err, users){
if(err){
responseObj.error = err;
}else{
responseObj.result = true;
responseObj.users = users;
}
res.send(responseObj);
});
}

// you need to call
exports.getUserById = function(req, res) {

var responseObj = new Object();
responseObj.result = false;

var id = req.params.id;

var searchQuery = { '_id' : id }; //format for search query

UserModel.findOne(searchQuery, function(err, user){
if(err){
responseObj.error = err;
}else{
responseObj.result = true;
responseObj.user = user;
}
res.send(responseObj);
});
}

exports.addUser = function(req, res){
var responseObj = new Object();
responseObj.result = false;

//In Post request, we can retrieve data by req.body object.

var userModelObj = new UserModel();
userModelObj.emailId = req.body.emailId;
userModelObj.firstName = req.body.firstName;
userModelObj.lastName = req.body.lastName;
userModelObj.password = req.body.password;

userModelObj.save(function(err){
if(err){
responseObj.error = err;
}else{
responseObj.result = true;
}
res.send(responseObj);
});

}

exports.updateUser = function(req, res){

var responseObj = new Object();
responseObj.result = false;

var id = req.params.id;

var searchQuery = { '_id' : id }; //format for search query

UserModel.findOne(searchQuery, function(err, user){
if(err || user == null){
responseObj.error = err;
res.send(responseObj);

}else{
user.emailId = req.body.emailId;
user.firstName = req.body.firstName;
user.lastName = req.body.lastName;
user.password = req.body.password;

user.save(function(err){
if(err){
responseObj.error = err;
}else{
responseObj.result = true;
}
res.send(responseObj);
});
}

});

}

exports.deleteUserById = function(req, res){

var responseObj = new Object();
responseObj.result = false;

var id = req.params.id;

var searchQuery = { '_id' : id }; //format for search query

UserModel.remove(searchQuery, function(err){
if(err){
responseObj.error = err;
}else{
responseObj.result = true;
}
res.send(responseObj);

});
}

GET /user

Now make a GET request to http://127.0.0.1:9000/user then we will get a list of all the users which are in the Database. For other POST, PUT & DELETE type of request, you can make use of any tool which allows creating HTTPRequest. For example, you can use “Poster” add on for the Firefox.

GET /user/:id

When we make calls like this http://127.0.0.1:9000/user/1, then it will return the user with matching userId.

POST /user

When we make call http://127.0.0.1:9000/user with a POST Type request, it will add new user information to the Database. With a Post request, we required to send some data and the type of data. In data part we send the user information in JSON format and set the content type as application/json and data will be like this:

{
“emailId”: “demo@example.com”,
“firstName”: “ABC”,
“lastName”: “XYZ”,
“password”: “123456”
}

PUT /user/:id

When we make call http://127.0.0.1:9000/user/1 with a PUT Type request, it will update user information in database with matching user id. So, here whatever data passed it will be assigned to user with having userId 1.

DELETE /user/:id

When we make call http://127.0.0.1:9000/user/1 with a DELETE Type request, it will remove user information from the database.

• Easy Development: Node runs on the JavaScript language. So, the web developer needs to learn only one language. So we can reuse the same code on both sides of the stack.

• High Performance & Scalability: Due to its non-blocking I/O architecture, we can achieve great performance with handling a big number of users.

• Ideal for Data-Heavy: Due to its non-blocking I/O architecture, it is best for the applications which required much database access than the operation which require computation. If your application required much computation, then Node.JS is not an ideal solution because it runs on single thread. So such operation can block other requests from clients.

• Open Source Community: Node.js has a great open source community which has produced many good modules to extend our application functionality with no effort. There are many modules available like PayPal Integration, Android/iOS Push Notifications API. For the entire module, there is one central repository available. You can access it from here.

Applications

• Real Time Applications: There are many applications which require live connections with the server. In other technologies like PHP, for each connection, it creates a new thread for handling operations for it. So, the number for live connection can be limited by the memory available to the server. While in node.js, all the connection is handled by the same thread. So, the server can handle many connections at the same time. For example, online games, chat programs etc.

• Backend APIs: Various big brands are using Node.js as a backend for their API which is accessed by mobile devices due to its fast, lightweight and scalable architecture.

• Websites: Because of its scalability and performance more and more people are stared using Node.js. There are various MVC Frameworks available in the market, which helps developers to create website with lesser efforts and front-end and backend can be done by JavaScript.
• Data Driven Applications: Node’s evented I/O model helps from various locking and concurrency issues which is possible in various multithreaded Async I/O Operations.