Developing Java Beans

Using JAR Files on the CLASSPATH

My class path is configured to look in the classes.zip file provided by the JDK, followed by the root directory of the packages that I am developing. The CLASSPATH environment variable looks as follows:

CLASSPATH=c:\jdk1.1\lib\classes.zip;c:\java\projects

We can include the JAR file on the class path the same way any other path is put there. For example, if I wanted to keep all of the packages developed for this book in the BeansBook.jar file instead of keeping them in separate files, I could modify my CLASSPATH variable to look as follows:

CLASSPATH=c:\jdk1.1\lib\classes.zip;c:\java\projects\BeansBook.jar

Now the HTML file for running the PickleUser applet can be restored to its original content by removing the ARCHIVES tag. In this case the PickleUser and BeansBook.util.PickleButton classes will be loaded from the BeansBook.jar file because it is part of the class path.

This technique works just fine as long as the JAR file is not compressed. (You can create a JAR file without compression using the command-line option). If you want to put a compressed JAR file on the class path, it must contain all entries for every subdirectory involved. If you want a compressed JAR file to contain BeansBook/Simulator/Thermostat.class, the JAR file needs entries for the following:

• BeansBook/

• BeansBook/Simulator

• BeansBook/Simulator/Thermostat.class