Open Source Shopping Cart Code
The following two lines of code are inserted into any HTML page that wishes to offer items for sale; I usually place them right after the <BODY> tag:
As mentioned earlier, one must add a CODEBASE=../, or some equivalent, to the <APPLET> tag when the HTML file is in a directory other than the one that contains the applet. A look at the source code posted elsewhere will give examples.
<APPLET code=app.class height=1
id=app name=app width=1 archive="app.zip"></APPLET>
<SCRIPT LANGUAGE=javascript>function buy(a,b,
c,d){document.app.prod(a,b,c,d)}</SCRIPT>
These lines load an applet called app.class. The code for "app" is as follows:
import java.applet.*;
public class app extends Applet
{
public void start()
{
ShopPanel.initValues(this);
}
public void prod(String iD, String it, String pr, String sh)
{
ShopPanel.prod(iD,it,pr,sh);
}
}
Let me make some comments for Open Source developers. First, the applet is the segment that is being reloaded, and it is short. This makes page to page transfer essentially instantaneous.
Second, HTML memory depends upon the applet being restarted, not reloaded. This appears to happen invariably, with an applet this size, in all current browsers. However, as features are added to the applet, one can begin to trigger a reload rather than a restart, particularly in HTML pages that are very complex. Pseudo-constructors continue to do their job; the result is a frame which persists, and whose purchases can still be finalized, but which is no longer accessible by any HTML page. It has become "detached." Further purchases bring up a second frame, which also persists. All further purchases are now added to the second frame. In order to keep size down, and to ensure restarting rather than reloading, Open Source programmers will probably find, as I have, that it is best to make changes in classes other than "app."
Third, notice that we call start() in the applet, and not init(). This is because init() is called the first time that an applet is loaded, whereas start() is called every time that a page transfer is made. Our goal is to update the rest of the code with the current address of the restarted applet every time the applet is reloaded. By passing on the value of "this", we can then use commands like "this.showDocument()." This continual updating can only be done by calling start().
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