Lecture 13 & 14 - Servlets - Advanced Topics

Question 1

Describe state in terms of Servlets?

Answer 1

•HTTP is stateless
–Once a webserver has dealt with a request the connection vanishes
–The server cannot recognize that a sequence of requests is from the same client

Question 2

What is the solution to avoid the lack of state?

Answer 2

Session Tracking
–Hidden form fields
–URL rewriting
–Cookies
–Sessions

Question 3

What are cookies?

Answer 3

• Information that a server gives to a client
• On request, the client returns the information

•Used for
–Identifying a user during an e-commerce (or other) session
–Avoiding user-name and password
–Customizing a site
–Focusing advertising

Question 4

What are the problems with Cookies?

Answer 4

• Some browsers do not support cookies
• Users can disable cookies
• Cookies cannot be larger than 4kb
• Only 20 cookies per domain
• No more than 300 cookies stored at client
• Expiry is up to browser (even though you can specify a value)

Question 5

Discuss servlets in regards to larger applications?

Answer 5

•Servlets cooperate to create content
•Multiple servlets in a chain
–request parameters supplied to first servlet
–output from each Servlet piped to the next Servlet in the chain
–last servlet in chain sends output to client

•Example use:
–Servlet #1: Translates XSQL page to XML page
–Servlet #2: Translates XML to HTML using XSL