Web Application Development

1. Web Application Development Lec 25

2. Web Application Development • we used J2SE until now • For web application development, we need J2EE (Servlets API, JSP API, JSF API etc)

3. Web Based Performance Review Management System

4. Web Based School Management System

5. What is a Web Application

6. 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

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

8. 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.

9. HTTP

10. 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

11. HTTP Request Example Request parameters etc

12. 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

13. HTTP Response Example

14. 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.

15. 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

16. Server Side Programming

17. Static Pages 1 - Request file 2 - Retrieve file 3 - Send file

18. Example: Static Page

19. Dynamic Pages 1 - Request service Do Computation Generate HTML page with results of computation Return dynamically generated HTML file

20. 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

22. Course Registration System

23. 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.

24. Dynamic Web Content Technologies Evolution (only figure) CGI (in C) CGI (java, C++) Template (ASP, PHP,CFML) complexity Speed, Security Servlet (Java) JSP

25. Web-Based Enterprise Applications in Java Figure shows a simplified view of one application and its layers.

26. Java Web Application Technologies(Presentation/Web Tier)