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

9.4 An On Line Store Using a Shopping Cart and Session Tracking

215

Figure 9 4

Result of the TechBooksPage servlet.

Handling the Orders

Listing 9.5 shows the servlet that handles the orders coming from the various

catalog pages shown in the previous subsection. It uses session tracking to

associate a shopping cart with each user. Since each user has a separate ses 

sion, it is unlikely that multiple threads will be accessing the same shopping

cart simultaneously. However, if you were paranoid, you could conceive of a

few circumstances where concurrent access could occur, such as when a sin 

gle user has multiple browser windows open and sends updates from more

than one very close together in time. So, just to be safe, the code synchro 

nizes access based upon the session object. This prevents other threads that

Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.

Servlet and JSP training courses by book's author: courses.coreservlets.com.