5-8 Lect Servlet1

8/7/2019 5-8 Lect Servlet1

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Session 1

Web Applications and

Servlets


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Session Objectives

Explain Web based application architecture

Explain the working of a webserver Describe the basics of HTTP

List and compare various server sidetechnologies

Describe the advantages of using servlets

Explore a servlets basic structure


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Exit

Bill

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A Day In A Typical Restaurant

This system runs smoothly runs with a few customer

Then the money

is paidThe customer asks

for the bill

A Waiter Accept the order

and then serves food

The customerleaves the

restaurant

A customer enters

the restaurant


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An example - McDonalds a Chain of Restaurants

Order

A customer enters

the restaurant

Collects the

items and leavesPays the bill

He places the order

He goes to the

counter...

Back end Chef

Food

Counter


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A Typical Restaurant

Client

Places order Passes it

Sends back the

processed order

ServesWaiter Chef

The restaurant may need to be expanded

Increased cost

Greater InvestmentThis can be a solution but

incase customers want to

place orders from a remote

location, then the web can

come to rescue


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The Web Based Solution -New way of doing

business - E-commerce

Web Server

receives request

(Waiter)

Places order HTTP request

Servlets act

as Chefs

Client Browser

Checks the

restaurant

database

Items are Present

Requests for Items

Dish

Ready

Information sent back to

client as an HTTP response


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The Web Application Architecture

Application Layer(2ndTier)

Response

Request

Presentation Layer(1stTier)

Web

BrowserWeb Server

Server Script a

Server side

program in Servlet

Data Stores

Data

Assembling

Database Layer

(3rdTier)

Web

Page

Webpage:Atext filecontainingtextalong withasetofHTML tags.

Awebserver respondstoa webbrowsers request forapageand

sends ittothe webbrowserthroughtheInternet

Webbrowser: Connectstoa Web Serverand interpretsasetofHTML tagswithin apagetodisplaythepageonthescreen.


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Various Server side Technologies

Java Server

Pages (JSP)

Server-side

Java Scripts (SSJS)Java Servlets

Proprietary Web serverAPIs (ISAPI, NSAPI)

Active Server

Pages (ASP)

Common GatewayInterface(CGI)

PHP

Server side Technologies


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How we see our web applicationYou use HTMLto say what aweb page is

and css to sayhow the page

should look

Var requestFunction

{

}

request

response

Web server


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Web Server

Server can support multiple concurrent

services

The Java Web Server is an instance of the

JVM

It may start several

services such as theHTTP service, Administrative service and

Web Proxy Service


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Servlets-defined Java objects which are based on

servlet framework and APIs and extend

the functionality of a HTTP server. Mapped to URLs and managed by

container with a simple architecture

Available and running on all major webservers and app servers

Platform and server independent


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Advantages of Servlets

Loaded in the same

process space as the

web server

Faster than common

scripting languages

More secure and almost

crash proof

Durable objects. Remain

in memory until

destroyed explicitly

Completely protocol

independent

Advantages


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Working of Servlet

HTTP

Services

Documents

5-8 Lect Servlet1