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<!DOCTYPE book [
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<section version="5.0"
         xml:id="schema-generation-invoking-schemagen-programatically"
         xml:lang="en" xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xmlns:ns5="http://www.w3.org/1999/xhtml"
         xmlns:ns3="http://www.w3.org/2000/svg"
         xmlns:ns="http://docbook.org/ns/docbook"
         xmlns:m="http://www.w3.org/1998/Math/MathML">
    <title>Invoking schemagen programatically</title>

    <para>Schemagen tools by default come in as CLI, ant task, and Maven
    plugin. These interfaces allow you to invoke schemagen functionality from
    your program.</para>

    <section xml:id="At_runtime">
        <title>At runtime</title>

        <para>If the classes you'd like to generate schema from are already
        available as <literal>java.lang.Class</literal> objects (meaning they are
        already loaded and resolved in the current JVM), then the easiest way
        to generate a schema is to use the JAXB API:</para>

        <example>
            <title>Generate schema at runtime</title>

            <programlisting language="java"><![CDATA[File baseDir = new File(".");

class MySchemaOutputResolver extends SchemaOutputResolver {
    public Result createOutput( String namespaceUri, String suggestedFileName ) throws IOException {
        return new StreamResult(new File(baseDir,suggestedFileName));
    }
}

JAXBContext context = JAXBContext.newInstance(Foo.class, Bar.class, ...);
context.generateSchema(new MySchemaOutputResolver());]]></programlisting>
        </example>
    </section>

    <section xml:id="CLI_interface">
        <title>CLI interface</title>

        <para>The <link
        xlink:href="http://fisheye5.cenqua.com/browse/jaxb2-sources/jaxb-ri/xjc/src/com/sun/tools/jxc/SchemaGenerator.java?r=jaxb-2_1-branch">CLI
        interface (<code>public static int
        com.sun.tools.jxc.SchemaGenerator.run(String[])</code>)</link> is the
        easiest API to access. You can pass in all the schemagen command-line
        arguments as a string array, and get the exit code as an int value.
        Messages are sent to <literal>System.err</literal> and
        <literal>System.out</literal>.</para>
    </section>

    <section xml:id="Ant_interface">
        <title>Ant interface</title>

        <para>Ant task can be invoked very easily from a non-Ant program. The
        schemagen ant task is defined in <link
        xlink:href="http://fisheye5.cenqua.com/browse/jaxb2-sources/jaxb-ri/xjc/facade/com/sun/tools/jxc/SchemaGenTask.java?r=jaxb-2_1-branch">the
        SchemaGenTask class</link>,</para>

        <para>For more about invoking an Ant task programatically, see the
        article <link
        xlink:href="http://www.fawcette.com/javapro/2004_06/magazine/features/kgauthier/">"Keep
        the Ant, Hold the XML"</link>.</para>
    </section>

    <section xml:id="Native_Java_API">
        <title>Native Java API</title>

        <para>The above two interfaces are built on top of externally
        committed contracts, so they'll evolve only in a compatibile way. The
        downside is that the amount of control you can exercise over them
        would be limited.</para>

        <para>So yet another approach to invoke schemagen is to use JAXB RI's
        internal interfaces. But be warned that those interfaces are subject
        to change in the future versions, despite our best effort to preserve
        them. This is the API that the JAX-WS RI uses to generate schema
        inside WSDL when they generate WSDL, so does some other web services
        toolkits that work with the JAXB RI.</para>

        <para>Most of those interfaces are defined and well-documented in
        <link
        xlink:href="http://fisheye5.cenqua.com/browse/jaxb2-sources/jaxb-ri/xjc/src/com/sun/tools/xjc/api">the
        com.sun.tools.xjc.api package</link>. You can see how the schemagen
        tools are eventually calling into this API at <link
        xlink:href="http://fisheye5.cenqua.com/browse/jaxb2-sources/jaxb-ri/xjc/src/com/sun/tools/jxc/apt/SchemaGenerator.java?r=jaxb-2_1-branch">the
        implementaion of SchemaGenerator class</link>.</para>
    </section>
</section>
