## Installing XOM

### Elliotte Rusty Harold

Copyright © 2005, 2016 Elliotte Rusty Harold

XOM is a library. By itself, it doesn't do much of anything. It exists only to be used by other programs. It requires Java 1.2 or later.

To install it you'll need to place the XOM JAR archive somewhere in your `CLASSPATH`. This archive is the file named something like `xom-1.2.10.jar`. (The version number may have changed if I've forgotten to update this document.) You can either put it in your `jre/lib/ext` directory, add `xom-1.2.10.jar` to your `CLASSPATH` environment variable, or use the `-classpath` option when invoking javac and java.

To check your download you can run one of the sample programs found in the `xom-samples.jar` file. For instance, `nu.xom.samples.PrettyPrinter` class formats an XML document by inserting and removing white space around element boundaries. In Java 1.4 and later you can run it from the command line like this:

    $ java -classpath xom-samples.jar:xom-1.2.10.jar nu.xom.samples.PrettyPrinter filename.xml

Java 1.3 and earlier do not have a built-in XML parser so in these environments you'll also need to install XOM's supporting libraries. These include `xalan.jar`, `xercesImpl.jar`, and `xml-apis.jar`, and are found in the `lib` directory. The versions shipped with XOM are quite a bit faster and less buggy than the ones bundled with the JDK, so you may well want to use them even in Java 1.4 and later. For example,

    $ java -classpath xom-samples.jar:xom-1.2.10:lib/xml-apis.jar:lib/xercesImpl.jar:lib/xalan.jar nu.xom.samples.PrettyPrinter filename.xml

You can leave out `xalan.jar` if you don't use any of the classes in `nu.xom.xslt`. `junit.jar` is only used for testing, and is not needed for normal operation of XOM.