The first step is to download XML for Java at
www.alphaworks.ibm.com/tech/ xml4j. Currently, you only need to
navigate to that site, click the Download button, then select a file
to download, and click the Download Selected File button. For
example, if you're on a UNIX system, you can select the file labeled
Binary distribution packaged as a UNIX Tar.gz file, which is
XML4J-bin.3.0.1.tar.gz as of this writing. If you're on Windows, you
can select the file labeled Binary distribution packaged as a Windows
ZIP file, which is XML4J-bin.3.0.1.zip as of this writing. You can
also download the XML for Java source code, which means that you can
build everything for yourself.
After you've downloaded the compressed XML for Java file, you must
uncompress it yourself (in Windows, make sure that you use an unzip
utility that can handle long filenames). That's all for actually
installing XML for Java-now you must make sure that Java can find
it.
Setting CLASSPATH
As far as we're concerned, XML for Java is a huge set of classes
ready for us to use. Those classes are stored in Java JAR (Java
Archive) files, and we must make sure that Java can search those JAR
files for the classes that it needs.
I discussed this process a little in the last chapter when I
mentioned using the Java CLASSPATH environment variable. This is the
variable that you set to tell Java where to look for additional
classes your code may require. In our case, the JAR files we'll need
to search for classes are called xerces.jar and xercesSamples.jar
(these names may have changed by the time you read this).
Unfortunately, the way you set the CLASSPATH variable can vary by
system. For example, to permanently set the class path in Windows NT,
you use the Control Panel. In the System Properties dialog box, you
click the Environment tab, then click the CLASSPATH variable, and
enter the new value there. In Windows 95 or 98, you can use the
MS-DOS SET command in autoexec.bat, which sets the value of
environment variables. Note, however, that you can also use the
MS-DOS SET command to set the class path in Windows 95, 98, and NT to
set the class path until the MS-DOS window is closed, which is
perhaps the easiest way. For example, if xerces.jar and
xercesSamples.jar are in the directory C:\xmlparser\XML4J_3_0_1 on
your system, you could use a SET command like this (and put it all on
one line):
C:\>SET
CLASSPATH=%CLASSPATH%;C:\xmlparser\XML4J_3_0_1\xerces.jar;
C:\xmlparser\XML4J_3_0_1\xercesSamples.jar
Take a look at the Java documentation to see how to set CLASSPATH
on your system. There's a shortcut if you can't get the CLASSPATH
variable working; you can use the -classpath switch when working with
the javac and java tools. For example, here's how I compile and run a
program named browser.java using that switch to specify the class
path I want to use (both commands should be on one line):
%javac -classpath C:\xmlparser\XML4J_3_0_1\xerces.jar;
C:\xmlparser\XML4J_3_0_1\xercesSamples.jar browser.java
%java -classpath C:\xmlparser\XML4J_3_0_1\xerces.jar;
C:\xmlparser\XML4J_3_0_1\xercesSamples.jar browser
We're ready to start working with code. I'll start by writing an
example that parses an XML document.
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