ant_customizations/antbuild.xml

<project name="Ant Customizations" default="all">
    <target name="all"   depends="build, publish"/>
    <target name="build" depends="jar"/>

    <target name="init">
        <property environment="env"/>
        <property name="ant.dir_temp"     value="${env.ANT_HOME}/lib"/>
        <pathconvert targetos="unix" property="ant.dir">
            <path>
                <pathelement location="${ant.dir_temp}"/>
            </path>
        </pathconvert>
        <property name="publish.dir" value=".."/>
        <property name="project.dir" value="."/>
        <property name="output.dir"  value="${project.dir}/output"/>
        <property name="src.dir"     value="${project.dir}/src"/>
        <property name="classes.dir" value="${output.dir}/classes"/>
        <property name="custom.jar"  value="ant_customizations.jar"/>
        <property name="custom.lib"  value="${output.dir}/${custom.jar}"/>
        <tstamp/>
        <echo message="ant.dir = '${ant.dir}'"/>
        <available file="${ant.dir}" type="dir" property="ant.exists"/>
    </target>

    <target name="pub_init">
        <available file="${publish.dir}/${custom.jar}" property="pub.jar.exists"/>
    </target>

    <target name="clean">
        <delete dir="${output.dir}" quiet="true"/>
    </target>

    <target name="compile" depends="init, clean">
        <mkdir dir="${classes.dir}"/>
        <javac
            srcdir="${src.dir}"
            destdir="${classes.dir}"
            debug="true"
            debuglevel="lines,vars,source"
            failonerror="false"
            includes="org/eclipse/persistence/**/*.java"
            classpath="${ant.dir}/ant.jar"
        />
    </target>

    <target name="jar" if="ant.exists" depends="compile">
        <delete file="${custom.lib}" quiet="true"/>
        <jar jarfile="${custom.lib}">
            <fileset
                dir="${classes.dir}"
                includes="**"
            />
        </jar>
    </target>

    <target name="test">
    </target>

    <target name="archive-old" if="pub.jar.exists">
        <move file="${publish.dir}/${custom.jar}" tofile="${publish.dir}/ant_customizations_bak_on_${DSTAMP}${TSTAMP}.jar"/>
    </target>

    <target name="publish" depends="init, pub_init, archive-old">
        <copy file="${custom.lib}" todir="${publish.dir}"/>
    </target>
</project>