First you'll need to download the source distribution from the XOM web site. This unpacks into a directory named "XOM".

XOM includes an Ant build file. You can build XOM with Ant 1.5 or 1.6. However, some targets require Ant 1.5 and some require Ant 1.6. Most targets can be built with Java 1.3 or later, but one target requires Java 1.5.

Building XOM requires Apache Ant. If you don't already have it installed, download it from http://ant.apache.org/. Be sure to add the ant/bin directory to your path and point the ANT_HOME enivronment variable to wherever you've installed Ant, as explained in the Ant documentation. Also set the JAVA_HOME environment variable to the location of your JDK,

Once you've done this, just type "ant" in the XOM directory to see the list of available targets:

[XOM]$ ant
Buildfile: build.xml

help:
     [echo]
     [echo] XOM Build file
     [echo] -------------------------------------------------------------
     [echo]
     [echo]   available targets are:
     [echo]
     [echo]     help      --> print this message
     [echo]     jar       --> build the xom.jar file
     [echo]     samples   --> build the xom-samples.jar file
     [echo]     compile   --> compile the source code
     [echo]     compile15 --> compile the classes that depend on Java 1.5
     [echo]     javadoc   --> generate the API documentation
     [echo]     betterdoc --> better formatted API documentation (requires Ant 1.6)
     [echo]     test      --> run JUnit test suite
     [echo]     testui    --> run Junit test suite in GUI
     [echo]     clean     --> clean up the build directory
     [echo]     dist      --> the zip and .tar.gz files
     [echo]
     [echo] -------------------------------------------------------------
     [echo]

BUILD SUCCESSFUL
Total time: 3 seconds

Most of these are self-explanatory. Typing "ant compile" compiles the source base into the directory build/classes. Typing ant jar compiles the files and stuffs them into a JAR archive. Typeing "ant javadoc" compiles the API documentation, etc. However, there are a couple of special cases to note:

XOM includes one class (nu.xom.JDK15XML1_0Parser) which can only be compiled by Java 1.5. This class is compiled by running the "ant compile15" target. Since not everyone has Java 1.5, the compiled version of this class is included with the source distribution and copied into the build/classes/nu/xom directory when the compile target is activated.

The XML parser used by Ant 1.6 sometimes gets in the way of XOM, due to obscure class loading issues. The unit tests ("ant test" and "ant testui") will probably only pass when using Ant 1.5. If anyone knows how to make the tests pass when run from Ant 1.6, I'd love to hear about it.