The Shopping Cart and Database
A non-commercial site is altered into a commercial site through the inclusion of two lines of "boilerplate code" into the HTML of all pages that wish to present items for sale. A specific item is then offered for sale by including an
onClick="buy('itemID','itemName','item
Price','itemShippingProcedures')"
event handler into any page object which is able to support it: this may be a button, a diagram, some region of an image, or even a JavaScript program. When the client operator triggers an event in this object on his browser, a call is made by the event handler to the applet or object which was loaded into the page, and the applet or object adds the item to a shopping cart frame or form which this applet or object brings up whenever a sale is made. None of this involves any interaction whatsoever with the host server.
When the "buy" event is triggered by the browser operator, the applet or object, in our particular implementation, checks to see whether an item with "itemID" is located in a cached database on the browser. If it is, then it assigns the associated cached price to the object, and displays this in the shopping cart frame or form. If it is not, then it uses the number that is hardcoded into the HTML as "itemPrice." Again, this involves no interaction with the host server. The fact that everything occurs on the client, and can use the full power of the client's processor, means that database access involves no noticeable delay, even when the database is quite large.
"itemID" is the key and must always be present. "itemPrice" may be an empty string. When it is, then the database must always be present, and it must contain "itemID" and a corresponding "itemPrice."
The database in our implementation is designed with Microsoft Access, and can thus be integrated into any large-scale database. It is a two column table in text format, and can thus also be designed by a novice operator using a simple text editor. To be recognized by the said applet or object, the database in our implementation must be stored on the merchant's server in the same directory as the applet or object, and it must be called "update.txt." When the applet or object is first loaded by some particular page, it checks for the presence of this file in its codebase directory. If the file is found, then the applet or object loads it, and it then generates a cache, on the client, for subsequent pages. In our implementation, this cache is a static String in an abstract JAVA class, and it persists. The string may be well in excess of 1 Meg in length, and could thus include more than 40,000 revisions. If the database file is absent, the applet or object remembers this as well-- in our case as an altered boolean variable in the JAVA code. No further server-client interaction is attempted, or necessary.
Once "itemPrice" has been checked with the (optional) database, which is cached on the client, then the applet or object, which also resides on the client, places the result in a frame or form on the desktop window. Sales information, as it accumulates, is stored as a static Vector in the JAVA code, and it persists. The result of the purchase can therefore be collated with prior purchases, and a running total developed and displayed.
Since cumulative sales information has persistence, it is possible to alter previous purchases without going back to the pages on which they were presented, and without interacting in any way with the host server. "UP" and "DOWN" buttons allow scrolling through the list of purchases, and "MORE" and "LESS" buttons allow prior purchasing decisions to be altered.
If "CLEARCART" is pressed, then the frame is made invisible. The "Window Close" button on the frame is not enabled because, as Open Source developers will discover, its use causes undesirable side effects.
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