I have an experience in this field,
At first, you should have an Schema that jaxb  create Objects from it.
and then you should write an ant task to do it (create objects from schema).
the lib should be these jar files :

1- activation.jar
2- jaxb1-impl.jar
3- jaxb-api.jar
4- jaxb-impl.jar
5- jaxb-xjc.jar
6- jsr173_1.0_api.jar

and ant task should be like this :

    <property name="jaxb.home" value="."/>

    <taskdef name="xjc" classname="com.sun.tools.xjc.XJCTask">
        <classpath refid="build.classpath"/>
    </taskdef>

    <target name="JAXB" description="Compile all java  source files">
        <echo message="Compiling the schema..."/>
        <xjc schema="view/schema/opxiActivityLog.xsd" package="com.project.opxi.manager.adaptor.JaxbObject" destdir="${opxi.src.dir}">
            <produces dir="${opxi.src.dir}/com/project/opxi/manager/adaptor/JaxbObject/JaxbObject" includes="**/*.java" />
        </xjc>
        <echo message="Compiling the java source files..."/>

        <javac destdir="${classes.dir}"
               debug="true"
               fork="true"
               source="1.5"
               classpathref="build.classpath">
            <src path="${opxi.src.dir}/${src.classes.prefix}/adaptor/JaxbObject"/>
            <!--<classpath refid="build.classpath" />-->
        </javac>
    </target>

Im really new into this jaxb  and if u can explain to me a bit what you
mean by creating an ant task it would be of great help.......