JavaOmar Rana

University of South Asia

Course OverviewJAVA

C/C++ and JAVA Comparison

OOP in JAVA

Exception Handling

Streams

Graphics User Interface

Event Handling

Game Programming

Graphics

Database Connectivity

Network Programming

J2EE

HTML / CSS

JavaScript

Servlets

JSP

JSF

JAVA Beans

JSP using XML Tags

MVC Architecture

Programming in Layers

XML technologies

Web Application

Java Categories

J2me

J2sdk

J2EE

J2EE Examples

Web Application Model

Request

Response

Communication model

Web server cannot distinguish if request is made from same browser or not

Its stateless

http doesn’t store any details how request is made

Different Clients

Web browsers

ftp clients

What is web server?

Webserver hosts website and offers protocol http

It takes request and response

It’s a software to provide services to access internet

Web server executes server side programmes

Example

Facebook login

User request something

Client response something

http protocol is used for communication

Example :

Pdf files, doc files

Http

Its a request – response model or oriented protocol

Http request contains the following:

Request Method

URI

Header Fields

Body

Http Response

Http Response contains:

Result code

Header Fields

Body

Http request Example

www.facebook.com

In Request following are sent:

GET-POST/

URI = home.html

http protocol

Headers :

Host : facebook.com

User –Agent : Google Chrome

Body :

Request parameters

HTTP response Example

Status line : tells if its error or ok response

Response headers :

Last modified: some date

Date: current date

Content type: html/text

content length: 50

Dynamic Website

Client Sends a request to server

Server side does some computation and response with html page with result generated of computation

Why dynamic pages and not static?

Dynamic Websites

www.google.com

Results depends on our query

www.facebook.com

Results depends on user login and database

J2EE APPLICATION STRUCTURE

JAVA web application technologies

Servlets

Its a java class

Servlets extend webserver to extend its capability

It allows us to compute on webserver and gives us a response

Request

Response

Servlets

Any class in java can be written in servlets

We don’t have to write http protocol mechanism

Rich set of libraries of java available in servlets

E.g.

JDBC

Multithreading

E.t.c

Servlet Advantages

Rich set of libraries

Built in multithreading – treats every request as multithread rather than creating new process

Portable across operating systems

Security – jvm verifier

Software's Required

Eclipse / net Beans

Tomcat Server

J2SE

J2EE

Servlet Hello World

To write Servlet we need to extend from

HttpServlet

Import javax.servlet.*;

Import javax.servlet.http.*;