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Web API Using Node Js

Introduction:

                To create a simple REST API for a database in SQL Server using Node.js and the two modules express (a Web framework for Node.js) and mssql (MS SQL Server client for Node.js). Returning results in JSON format that can easily be treated by a web application, mobile, another REST service, etc.

                In this section, you will learn how to create a web application using Express.js. Express.js provides an easy way to create web server and render HTML pages for different HTTP requests by configuring routes for your application.

                Express is a fast, unopinionated minimalist web framework for Node.js. Express.js is a web application framework for Node.js. Express.js provides an easy way to create web server and render HTML pages for different HTTP requests by configuring routes for your application.

Steps and Verification:

Step 1:

Install the modules mssql and express using commands npm install mssql and

npm install expess   using command prompt.

ExpressandMSSQLModules

Step 2:

Import the Express.js module and create the web server as shown below.

webserver.js: (file name)

var express = require('express');

var app = express();

var config = {

    "user": 'sa',

    "password": '########',

    "server": '#######\\SQLEXPRESS',

    "database": 'master',

    "port": '1433',

    "dialect": "mssql",

    "dialectOptions": {

        "instanceName": "SQLEXPRESS"

    }

};

// define routes here..

 

var server = app.listen(8080, function () {

    console.log('Node server is running..');

});

In the above example, we imported Express.js module using require() function. The express module returns a function. This function returns an object which can be used to configure Express application (app in the above example).

The app object includes methods for routing HTTP requests, configuring middleware, rendering HTML views and registering a template engine.

The app.listen() function creates the Node.js web server at the specified host and port. It is identical to Node's http.Server.listen() method.

Run the above example using node webServer.js command and point your browser to http://localhost:8080. It will display Cannot GET / because we have not configured any routes yet.

Step 3: [Configure routes] Use app object to define different routes of your application. The app object includes get(), post(), put() and delete() methods to define routes for HTTP GET, POST, PUT and DELETE requests respectively.

The following example demonstrates configuring routes for HTTP requests.

webserver2.js: (file name)

var express = require('express');
var app = express();
 app.get('/', function (req, res) {
res.send('<html><body><h1>Hello World</h1></body></html>');
});
 app.post('/submit-data', function (req, res) {
    res.send('POST Request');
});
 app.put('/update-data', function (req, res) {
    res.send('PUT Request');
});
 app.delete('/delete-data', function (req, res) {
    res.send('DELETE Request');
});
 var server = app.listen(8080, function () {
    console.log('Node server is running..');
});

SimpleAPIUsingNode

In the above example, app.get(), app.post(), app.put() and app.delete() methods define routes for HTTP GET, POST, PUT, DELETE respectively. The first parameter is a path of a route which will start after base URL. The callback function includes request and response object which will be executed on each request.

Run the above example using node webServer2.js command, and point your browser to http://localhost:8080/ and you will see the following result.

Below figure showing the command prompt window

ServerIsRunning


Below figure showing the web page result in browser

HelloWorldExample.png

There is another example for Post method shown below.

var express = require('express');

var path = require('path');

var app=express();

var bodyParser = require("body-parser");

app.use(bodyParser.urlencoded({ extended: false}));

app.get('/', function (req, res) {

      res.sendFile(path.resolve('index.html'));

});

app.post('/submit-student-data', function (req, res) {

      var name = req.body.firstName+ ' ' +req.body.lastName;

      res.send(name+'Submitted Successfully!');

});

var server = app.listen(8080, function () {

      console.log('Node server is running..');

});

Html File[index.html(File name)]:

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta charset="utf-8" />

<title></title>

</head>

<body>

<form action="/submit-student-data" method="post">

First Name: <input name="firstName" type="text" /> <br />

Last Name: <input name="lastName" type="text" /> <br />

<input type="submit" />

</form>

</body>

</html>

GetandPostExample

Run the above example using node webServer2.js command, and point your browser to http://localhost:8080/ and you will see the following result.

Below figure showing the command prompt window

ServerRunningTwo

Below figure showing the web page result in browser

SampleHtmlFileRender If you click on submit button show next page like below.

DetailsSubmitted


To retrieve data from the web page, we can use below methods.

1.   req.query.variableName: It is used to retrieve data from Url-query from web page.

2. req.body.textboxName: It is used to retrieve data from text boxes or inside the body from web

About Author
Madhavi Seethi
Total Posts 3
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