Session Tracking

Why?

When clients at an on line store add an item to their 

shopping cart, how does the server know what's already 

in the cart?

When clients decide to proceed to checkout, how can the 

server determine which previously created shopping cart 

is theirs?

How?

Cookies

URL rewriting

Hidden form fields

Higher level API needed

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The Session Tracking API

Session objects live on the server

Automatically associated with client via 

cookies or URL rewriting

Use 

request.getSession(true)

to get either existing or new 

session

Behind the scenes, the system looks at cookie or 

URL extra info and sees if it matches the key to some 

previously stored session object. If so, it returns that 

object. If not, it creates a new one, assigns a cookie 

or URL info as its key, and returns that new session 

object.

Hashtable like mechanism lets you store 

arbitrary objects inside session

setAttribute

stores values

getAttribute

retrieves values

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