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Java for the Webmaster: All Gain No Pain

Troubleshooting

There any many small problems that can pop up as you're adding an applet to your page. I often encounter them myself as I'm adding new applets to the Java Boutique. Sometimes the applet works fine on the author's page, but simply refuses to work on mine. It happens to the best of us, so don't be discouraged if it happens to you. We'll try to go over some tips here to help save you some time and frustration.

If you see "Applet can't start: class ______ not found" in your browser's status line (the area of your browser closest to the bottom of the screen), it can mean one of two things:

1. The class file(s) are not named correctly in your code or on your Web server. Java is case-sensitive, so be sure to follow precise capitalization when coding or copying files to the server.
2. The class file(s) are not in the correct directory. They should be located in the path indicated in the CODEBASE portion of the APPLET tag if you are using one, or in the directory with your HTML document if no CODEBASE is specified.

To further enable you to locate the problem, you may want to start what's known as the Java Console (under MSIE or NS). If you're using Netscape, you'll find it under the Communicator item in the Netscape menu (Java Console). Using MSIE, you'll usually find it under View (Java Console) in the MSIE menu. The Java Console will provide you with more details than the status bar, and may help you locate the reason why the applet will not run. Often, it will show you that the applet depends on more than one class file and it can't locate the additional class file, so you'll need to upload that class file to your server as well, once you determine what it is.

At times, the applet may have been written to a newer version of the JDK than you have installed on your system. Most applets will work with MSIE4 and Netscape4 upward, but you may want to test the applet on both browsers just to be sure. If the applet only works with the ultra-newest version of a browser or Java feature-set, be sure to let your visitors know that before they go tearing their own system apart looking for a solution.

Some applets may not work at all on your local system, but will work fine from your remote Web server, so you may want to test it there as well before you give up. Others are just the opposite, and will only work locally, and may require you to purchase a license in order to be used remotely on your site.

NEXT

This article first appeared in October, 1998

How to Add Java Applets to Your Site

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