build.xml

<?xml version="1.0" encoding="UTF-8"?>
<project name="DemoProject" default="jar" basedir=".">

    <!-- ===== Properties ===== -->
    <property name="src.dir" value="src"/>
    <property name="build.dir" value="build"/>
    <property name="classes.dir" value="${build.dir}/classes"/>
    <property name="jar.dir" value="${build.dir}/jar"/>
    <property name="lib.dir" value="lib"/>
    <property name="main.class" value="com.training.Main"/>

    <!-- ===== Clean ===== -->
    <target name="clean">
        <delete dir="${build.dir}"/>
    </target>

    <!-- ===== Compile ===== -->
    <target name="compile" depends="clean">
        <mkdir dir="${classes.dir}"/>

        <javac srcdir="${src.dir}"
               destdir="${classes.dir}"
               includeantruntime="false"
               debug="true">
            <!--<classpath>
                <fileset dir="${lib.dir}" includes="*.jar"/>
            </classpath>-->
        </javac>
    </target>

    <!-- ===== JAR ===== -->
    <target name="jar" depends="compile">
        <mkdir dir="${jar.dir}"/>

        <jar destfile="${jar.dir}/MyJavaProject.jar" basedir="${classes.dir}">
        	<zipgroupfileset dir="${lib.dir}" includes="*.jar"/>
            <manifest>
                <attribute name="Main-Class" value="${main.class}"/>
            </manifest>
        </jar>
    </target>

</project>