Prentice Hall and Sun Microsystems. Personal use only; do not redistribute.

Chapter

his chapter shows you how to use the servlet session tracking API to

keep track of visitors as they move around at your site.

T

9.1 The Need for Session Tracking

HTTP is a  stateless  protocol: each time a client retrieves a Web page, it

opens a separate connection to the Web server, and the server does not auto 

matically maintain contextual information about a client. Even with servers

that support persistent (keep alive) HTTP connections and keep a socket

open for multiple client requests that occur close together in time (see Sec 

tion 7.4), there is no built in support for maintaining contextual information.

This lack of context causes a number of difficulties. For example, when cli 

ents at an on line store add an item to their shopping carts, how does the

server know what's already in them? Similarly, when clients decide to proceed

to checkout, how can the server determine which previously created shop 

ping carts are theirs?

There are three typical solutions to this problem: cookies, URL rewriting,

and hidden form fields. 

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