Chapter 14. Offline Order Processing Using Store-and-Forward

In the always-on post-Internet world, instant worldwide connectivity is often taken for granted. This was brought home to me rather abruptly when my ISDN connection through my local telephone company went down one sunny Friday afternoon, and stayed down for 11 days. Sure, it would occasionally come up for 10 minutes here, a couple of hours there. But the fact was that most of the time my little home network was on its own, adrift. For a programmer, writer, and e-mail junkie, this was a far-from-acceptable situation.

Ten years ago, incomplete and unreliable networks were the rule, not the exception. Systems had to be built to accommodate these little unexpected outages, and take advantage when connectivity was available. Even though my new cable modem service has been down only a handful of times (and never for more than an hour), building reliable systems will never go out of style.

Technologies Used:

• Java

• JDOM

• SMTP

• POP3

Despite the appealing vision of an always-on wireless Internet connection, there are still many situations in which connectivity just won't be available. Even if perfect wireless access were an option (which it isn't), rural areas, airplanes, and shielded buildings would still require solutions that don't depend on continuous connectivity. This chapter shows how XML can be used as a data format for an asynchronous messaging application.