How to Add Java™ Applets to Your Site

A lot of sites feature Java applets, and if you've been searching through the Java Boutique's applet library, you may have found an applet you'd like to add to your own site. This guide will help you to do just that, and will point out some common problems and tips to simplify the task. You may also want to read Java for the Webmaster and Java On Your Site to find out more about selecting and using the proper applets for your Web site.

The assumption is made that you are able to run Java on your computer system. If you have problems viewing Java applets, you can find help at: http://www.microsoft.com/java/

1. First, select the Java applet you would like to add to your site. Many of the applets are free with some requiring only a link back to the author's site. Others have a link to the author's site written in them which can be removed by paying a registration fee. Still others require a fee before they can be used.

2. Download the zip file to a directory on your computer (make sure you remember the directory where you downloaded it). The zip file contains the necessary files to run the Java applet.

   In a few cases, you must download the jar or class files individually. Note that in Netscape Communicator, you must hold down the shift key and then click the link to download the files.

   Another alternative would be downloading the .JAVA source code, if it is available, and compiling it using the Java Compiler that is included with the Sun Microsystems Java Developers Kit or this Java Compiler Service.

3. In order to run the applet, it must be loaded by an HTML file. This would be the Web page you want to display the applet on, i.e. your home page. Many times the author has included an example in the zip file. (If the applet comes from the Java Boutique, the HTML source is included on the applet page for you to copy) The code ("HTML source") will look something like the following:

   <applet code=NameOfApplet.class name=NameOfApplet archive=NameOfApplet.jar width=300 height=300> <param name="bgcolor" value="ffffff"> <param name="fontcolor" value="000000"> Your browser is not Java enabled. </applet>

   Note: The term "code" points to the class file, which contains the applet code; "archive" points to the file that contains the class files. You can leave the zip file intact and just point to it i.e. archive="NameOfApplet.zip". Many applets have a "param" listing. This is to list the parameters for the item mentioned, in this case the background color ("bgcolor") and the font color ("fontcolor"). The "value" is the value assigned to the parameter. This information should be contained in the zip file.

4. If the Applet requires image and/or sound files (generally .GIF, .JPG, and .AU files), place them in the appropriate directories as indicated on the applet page.

5. You are now ready to test the applet using a Java-enabled browser.

6. Assuming the applet loaded successfully, you can now move your files to your Web server. These should either all be in the same directory or the HTML source code should point to the directory where the class and/or zip files are, i.e. "CODEBASE=DirectoryNameWhereClassFilesReside".

   Upload the HTML file and the image and/or sound files. You will also need to upload all the files that were included in the applet zip file. If some of the files have a "$" in the name — i.e. this$file.class — you may not be able to upload them to the server. In that case, just use the "archive" parameter and point to the zip file: archive="NameOfApplet.zip". The applet will pull the code directly from the zip file.

   

7. Finally, crediting the author of the Applet (as well as the Java Boutique) on your page would probably be a nice finishing touch. Feel free to copy the button to the right or use the following code to incorporate it into your page:

   <a href="/old?u=http%3A%2F%2Fjavaboutique.internet.com&y=1999"> <img alt="The Java Boutique" src="/old?u=http%3A%2F%2Fjavaboutique.internet.com%2Fimg%2Fjavabtq_button.gif&y=1999"></a>

Troubleshooting

If you see "Applet can't start: class ______ not found" in your browser's status line, it can mean one of two things:

1. The .class file(s) are not named correctly. Java is case-sensitive, so be sure to follow precise capitalization.
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, or the directory of your HTML document if no CODEBASE= is specified.

To further enable you to locate the problem, you may start 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 find it under View (Java Console) in the MSIE menu. The Java Console will give you more details than the status bar, and may help you find out why the applet will not run. Often, it will show you that the applet depends on more than one class file, and you'll need to upload that class file to your server as well.

The applet may be written for a newer JDK than you have on your system. Most applets will work with MSIE4, and Netscape4 as well, provided you have applied the latest JDK 1.1 patch from http://developer.netscape.com.

For more help, you can try consulting the Java FAQs or posting a message to one of the java newsgroups:

• comp.lang.java.advocacy
• comp.lang.java.api
• comp.lang.java.beans
• comp.lang.java.corba
• comp.lang.java.databases
• comp.lang.java.gui
• comp.lang.java.help
• comp.lang.java.machine
• comp.lang.java.misc
• comp.lang.java.programmer
• comp.lang.java.security
• comp.lang.java.softwaretools
• comp.lang.java.tech