Web Applications

Contents: Introduction to web? What is web applications Components Web application interaction? Webservers? Examples of web servers? Website vs web servers? Web application deployments? Advantages of web application? Disadvantages of web applications?

Introduction to Web

• Web features• Clent/Server• HTTP• HyperText Markup Language• URL addresses

• Web server - a computer program that is responsible for accepting HTTP requests from clients and serving them HTTP responses

• Web application - a dynamic extension of a web or application server

What is web application?

Web applications run through a web browser like Internet Explorer. The program sits on a web server, rather than on the PC, or local server for traditional applications.

On a basic website pages are static. Web application pages interact with users requesting and responding to users

. The most common example is online shopping application.

Web applications typically use a database to store permanent information such as product descriptions and costs, and customer orders.

Web Applications deliver many business benefits compared to office based solutions.

Web Applications & Components• Two types of web applications:• Presentation-oriented (HTML, XML pages)

• Service-oriented (Web services)

• Web components provide the dynamic extension capabilities for a web server:• Java servlets

• JSP pages

• Web service endpoints

Web Application Interaction• client sends an HTTP request to the web server

• web server HTTP request HTTPServletRequest• This object is delivered to a web component, which can interact

with JavaBeans or a DB to generate dynamic content

web component generates an HTTPServletResponse or pass the request to another web component

• web server HTTPServletResponse HTTP response

• web server returns HTTP response to the client

Web Application Interaction

Web Components• Servlets - Java classes that dynamically process requests and construct responses

• JSP pages - text-based documents that execute as servlets but allow a more natural approach to creating static content

• Servlets - service-oriented applications, control functions

• JSP - generating text-based markup (HTML, SVG, WML, XML)

Java Web Application Technologies

Java Servlet technology is the foundation of all the web application technologies

What are web servers ?

• The software (the computer application) that helps to deliver content that can be accessed through the Internet.

• The most common use of web servers is to host websites

• There are other uses such as gaming, data storage or running enterprise applications.

• A web server serves web pages to clients across the Internet or an Intranet. The web server hosts the pages, scripts, programs, and multimedia files and serves them using HTTP, a protocol designed to send files to web browsers and other protocols.

What is a Web Server?Web Server is a computer with special software

to host the web pages And web applications.

Commonly used web server software

applications are Apache

IIS

Web Site Vs Web Servers

Web site – Collection of web pages

associated particular host name.

Web Server – A program that satisfies the

client’s requests for web resources.

How Web Servers Work?

Example of Web Servers….

• Apache HTTP Server-Developed by Apache software foundation.- Supports most of the OS like Unix, Linux, Novell Netware, Windows, Mac OS X, Solaris, and FreeBSD.

• Microsoft Internet Information Services (IIS)- Supports only on Windows platform

• Sun Java System Web Server- Web Server is designed for medium to large business applications. Sun Java System Web Server is available for most operating systems.

How it Works ….?

Web Containers• Web components are supported by the services of a runtime platform called a web container

• In J2EE, a web container "implements the web component contract of the J2EE architecture“

• Web container services: • request dispatching • security • concurrency• life-cycle management• naming, transactions, email APIs

Web Container Examples• Non-commercial• Apache Tomcat• Jetty

• Commertial• Sun Java System Application Server • BEA WebLogic Server• Oracle Application Server• WebSphere

• Open source• JBoss

Deployment• Web components have to be installed or deployed to the web container

• Aspects of web application behaviour can be configured during application deployment

• The configuration information is maintained in a XML file called a web application deployment descriptor

Web Application Development• A web application consists of:• Web components

• Static resource files (such as images)

• Helper classes and libraries

• The process for creating and running a web application is different from that of traditional stand-alone Java classes

Advantage of web applications??? Zero install - all PCs have a browser Reduce business costs - less time spent talking to

customers over the phone; eliminate printed materials; allow users to update their own details

Centralised data is secure and easy to backup Quick and easy updates Reach anybody, anywhere in the world. Available 24 hours a day, 7 days a week Direct access to latest information - for Employees where

every they are located. Always up-to-date

Disadvantages of Web Applications Slower, as run over the internet Internet not always 100% available Can take longer to develop as they are more complex Have to support different browsers, and different versions Security risks