Web Application Development

Web Application Development

Lec 25

Web Application Development we used J2SE until now

For web application development, we need J2EE (Servlets API, JSP API, JSF API etc)

Web Based Performance Review Management System

Web Based School Management System

What is a Web Application

HTTP Communication Model

A communications model• Client, often but not always a web browser, sends a request for a resource to a server.•The server returns a response or an error message.• Stateless

• No immediate feedback• No details on how request is made

HTTP Communication Model

Different clients like•Web browsers •FTP clients (e.g., interarchy on MacOS X)•Software registration programs•telnet

HTTP Communication Model

Web Server?Software that provides services to access the Internet, or an intranet.

A web server hosts web sites Provides support for HTTP and other protocols Executes server-side programs (such as CGI scripts or servlets) that perform certain functions.

HTTP

HTTP Basics

HTTP is a request-response oriented protocol. Parts of an HTTP request

Request Method URI Header Fields Body

HTTP response contains Result Code Header Fields Body

HTTP Request Example

Request parameters etc

Request Parameters

Request can also contain additional info in the form of parameters In the URL itself as a query string http://www.gmail.com/register?name=ali&state=punjab

As part of the request body Shown earlier in the diagram

HTTP Response Example

HTTP Response Codes

Codes fall into five general categories 100-199

Codes in the 100s are informational, indicating that the client should respond with some other action.

200-299 Values in the 200s signify that the request was successful.

300-399 Values in the 300s are used for files that have moved and

usually include a Location header indicating the new address.

400-499 Values in the 400s indicate an error by the client.

500-599 Codes in the 500s signify an error by the server.

Common HTTP Response Codes 200: means every thing is fine.

404: Indicates that the requested resource is not available

401: Indicates that the request requires HTTP authentication

403: Indicates that access to the requested resource has been denied

503: Indicates that the HTTP server is temporarily overloaded and unable to handle the request

Server Side Programming

Static Pages

2 - Retrieve file

3 - Send file

1 - Request file

Example: Static Page

Dynamic Pages

Do Computation

Generate HTML page with resultsof computation

Return dynamically generated HTML file

1 - Request service

Why build Pages Dynamically?

The Web page is based on data submitted by the user E.g. results page from search engines and order

confirmation pages at on line stores

The Web page is derived from data that changes frequently E.g. a weather report or news headlines page

The Web page uses information from databases or other server-side resources E.g. an e-commerce site could use a servlet to build a

Web page that lists the current price and availability of each item that is for sale\

Course Registration System

Course Registration System

What is Server-Side Programming (SSP)?

Technologies for developing web pages that include dynamic content.

Can produce web pages that contain information that is connection- or time-dependent.

Dynamic Web Content Technologies Evolution (only figure)

CGI(in C)

Template(ASP, PHP,CFML)

Servlet(Java)

CGI(java, C++)

JSP

Speed, Securitycomplexity

Web-Based Enterprise Applications in Java

Figure shows a simplified view of one application and its layers.

Java Web Application Technologies(Presentation/Web Tier)