For most projects I’ve been working on lately, I have had to implement a library or an application starting from an XML schema file. There are several ways to generate Java classes from a schema (this process is called binding a schema to a Java representation). Of course, working at SUN, I naturally started with using JAXB

A key element of this binding process is the compiler that generates those Java classes. In JAXB, this task is dedicated to XJC. In order to call XJC you can either run it from the command line or, even better, invoke it directly from your NetBeans project. To do the latter, you will need to modify or add a few files to your project: the overall build.xml of the project and a catalog.xml and a binding.xml that relates directly to the schema(s) you have to start with.

First, you need to add a new target in your build.xml file to instruct NetBeans to generate the code and where to put those classes:

    <target name=”-pre-compile”>
        <echo message=”Compiling the schemas…”/>
        <mkdir dir=”build/gen-src”/>
        <xjc catalog=”Schemas/catalog.xml” binding=”Schemas/binding.xml” destDir=”build/gen-src”>
            <schema dir=”Schemas/”>
                <include name=”*.xsd”/>
            <produces dir=”build/gen-src/com/sun/myproject” includes=”**/*.java”/>

Don’t forget to explicitly declare where XJC can be found. On my Mac, it would look like:

    <taskdef name=”xjc” classname=””>
            <fileset dir=”/Applications/NetBeans/…/ext/jaxws21″ includes=”**/*.jar”/>

Once this is done, you’ll need to add a catalog.xml file in the schemas directory (or elsewhere). In a nutshell you declare where other resources (like schemas your own schema may depend upon) can be found (e.g. in a local directory or online). An example of such mapping would be:

<?xml version=”1.0″ envoding=”UTF-8″?>
<catalog xmlns=”urn:oasis:names:rc:entity:xmlns:xml:catalog” prefer=”system”>
   <system systemId=”; uri=”w3-dsig/w3-2002-12-xenc-schema.xsd”/>
   <uri name=”; uri=”w3-dsig/w3-2002-12-xenc-schema.xsd”/>
   <system systemId=”; uri=”w3-dsig/w3-2000-09-xmldsig-core-schema.xsd”/>
   <uri name=”; uri=”w3-dsig/w3-2000-09-xmldsig-core-schema.xsd”/>

You also need, and this is the 3rd file I mentioned, to have a binding.xml file which, among many other things, describes the mapping of the schemas to be compiled with your project structure/hierarchy. For instance, you can say that the Java classes created from the schema w3-2000-09-xmldsig-core-schema.xsd should be packaged as org.w3.xmldsig. An example of such file is below:

<jxb:bindings version=”2.1″

    <jxb:bindings schemaLocation=”rest-ds.xsd” node=”//xs:schema”>
            <jxb:package name=”com.sun.silverlining.identity”/>

    <jxb:bindings schemaLocation=”wssecurity-200401-secext-1.0.xsd” node=”//xs:schema”>
            <jxb:package name=”oasis.wss.secext”/>

    <jxb:bindings schemaLocation=”wssecurity-200401-utility-1.0.xsd” node=”//xs:schema”>
            <jxb:package name=”oasis.wss.utility”/>
    <jxb:bindings schemaLocation=”liberty-idwsf-utility-v2.0.xsd” node=”//xs:schema”>
            <jxb:package name=”liberty.util”/>


Don’t forget to instruct NetBeans to look for those newly generated classes. for this, in NetBeans, go to the properties of your project and look at the Sources in the Categories tab. There you should add the folder you declared in the build.xml file (in the above example: build/gen-src).

That’s it!
Building your project should now automatically generate Java classes from the schema and then build the whole project.