This document discusses web applications and their architecture. It describes the HTTP protocol used to send requests and responses over the internet. A typical web application uses a three-tier architecture with presentation, business, and data tiers. The document outlines the web application development process and demonstrates how to configure Tomcat server in Java Studio Enterprise.

1. Session 1
Web Applications – An Overview

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Objectives
Describe a multi-level architectural view of a
Web application.
Review HTTP protocol
Describe the anatomy of a typical Web
Application.
Describe the Web development process
Setup Tomcat environment in Java Studio
Enterprise 8.

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Desktop Applications 2-1
User Windows Media Player
User selects an mp3 file
Media Player playing the mp3 file

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Desktop Applications 2-2
User Windows Media Player
Request = Select a file to play
User sends a request
Player sends a response
Response = Media Player plays the selected file
Media Player is an example of desktop application

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Web Applications 2-1
Web Site hosted on a
Web Server
www.mp3.com

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Web Applications 2-2
www.mp3.com Web Application
Web Application running on a Web Server
User requests a song
Song is played in response
Advantages of Web Applications:
•Accessing Web Applications is easier
•Maintenance and deployment costs are low

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HTTP Protocol 3-1
Get File HTTP
GET
image/bar01.jpg
HTTP/1.1
HTTP/1.1 200 OKFile Received
HyperText Transfer Protocol
Stateless protocol
Used to send request and response messages over the
Internet.
Uses port 80 to send and receive messages

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HTTP messages consist of:
Request
Response
Headers
HTTP Protocol 3-2
Request Message
Request Line
Header Information
Method Resource Name Version
GET/POST bar01.jpg HTTP/1.1
Browser Type Content Type
User-Agent: Mozilla/4.0 (Compatible; MSIE 4.0 : Windows 95
Accept: image/gif, image/jpeg, text/*, */*
Response Message
Status Line
Header Information
Version Status Code Description
HTTP/1.1 200 OK
Server
Software
Modified
Date
Size
(bytes)
Content
Type
Server: JavaWebServer
Last modified: Tuesday, 07-Sep-04 1:14:34 GMT
Content-length: 100
Content-type: text/plain

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HTTP Protocol 3-3
HTTP protocol uses the following methods to send
request messages:
 GET Method
 POST Method
 GET Method
 Used for retrieving information such as
document, charts, or database query
results.
 Requested pages can be bookmarked and
emailed.
 Request information is sent as query string
 POST Method
 Used to send sensitive information such as
credit card numbers or information to be
saved in the database.
 Requested pages cannot be bookmarked
or emailed.
 No size limit on information being sent
query string
(240-255 characters)

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Application Architecture
Software Application Components
-Presentation Logic
-Application Logic
-Data Access Logic
Types of Architecture
-One-Tier
-Two-Tier
-Three-Tier
Data Access
Business
Presentation
Data Access
Business
Presentation

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Web Application Architecture
Web Applications use Three-tier architecture
Presentation Tier
Clients
Business Tier
Web Server
Database
Data Tier

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Web Application Directory Structure
Web Application
 HTML files
 Images
 Servlets
 JSP pages
 JavaBeans
 Jar files
 Applets
 Tag files
 Tag Library
Descriptor files
 Deployment
descriptors
.war file
Document Root
Static Files(html, images, JSP) WEB-INF
lib tags .tld, web.xmlclasses
Web Application Directory Structure
index.html, login.jsp, contactus.jsp
ViewBooks.jsp, logo.jpg
book1.jpg
AddBook.class,
DeleteBook.class
mbase.jar,
msqlserver.
jar,
msutil.jar
DisplayBook.tag web.xml, books.tld

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Web Application Development Process
Design a directory structure
Write web application code
Write deployment descriptor
Compile the code
Package web application
Deploy web application
Execute web application

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Tomcat Configuration
Demonstration
Steps to configure Tomcat in Java Studio
Enterprise 8
Select ToolsServer Manager

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Summary
 Web applications are easy to maintain, upgrade and
deploy as compared to desktop applications.
 Pages requested using GET method can be bookmarked
and emailed.
 POST method is used when sending sensitive
information such as credit card numbers, passwords and
so on.
 In three-tier architecture, the presentation tier cannot
interact with the data tier.
 JBuilder Enterprise 2005 can be configured to use
external Tomcat installation.