Referring 3rd party Jars within your Jar /lib : MANIFEST.mf Class-Path

As per my current understanding, you cannot refer any third party utility Jars which you placed in your apps /lib folder, when you export it as a Jar. 

Say yourJar.jar has lib/log4j.jar.  But your main class cannot load the log4j classes

http://www.velocityreviews.com/forums/t130458-executable-jar-classpath-problem.html 

The workaround for this situation: Place those utility/thrid party Jars in the same directory or inner directories, where your Jar is placed and making sure that that relative path is mentioned in the Manifest.mf Class-path Header.

<!-- This build script will help you build your own Jar, with utility Jars exported with

and all those Jars added to the MANIFEST.mf Class-Path header

-->

<project

name="buildJar" default="build-jar" basedir=".">

<!-- Add all the jar files in lib folder to the class path -->

<path id="build.classpath">

<fileset dir="${basedir}/">

<include name="lib/*.jar" />

</fileset>

</path>

<!-- Copy all Jars name to the Class-Path; keep an eye on the SPACE seperator -->

<pathconvert property="project.manifest.classpath" pathsep=" lib/">

<path refid="build.classpath" />

<mapper>

<chainedmapper>

<flattenmapper />

<globmapper from="*.jar" to="*.jar" />

</chainedmapper>

</mapper>

</pathconvert>

<target name="clean">

<delete dir="bin" />

<mkdir dir="bin/lib" />

<delete dir="build" />

<mkdir dir="build" />

</target>

<target name="copy-inner-jar-files">

<copy todir="bin/lib" includeemptydirs="false">

<fileset dir="lib" includes="*.jar" />

</copy>

</target>

<target name="copy-non-java-files">

<copy todir="bin" includeemptydirs="false">

<fileset dir="src" includes="**/*" />

</copy>

</target>

<target name="compile-jar-classes" depends="clean,copy-non-java-files, copy-inner-jar-files">

<javac srcdir="src" destdir="bin" classpathref="build.classpath" />

</target>

<target name="build-jar" depends="compile-jar-classes" >

<jar basedir="bin" jarfile="${basedir}/build/MyJar.jar">

<fileset dir="build" />

<manifest>

<attribute name="Main-Class" value="com.sree.test.jar.MyInnerJarTesterMain" />

<!-- <attribute name="Class-Path" value=" . lib/junit-4.10.jar lib/log4j.jar lib/ojdbc14.jar" /> -->

<attribute name="Class-Path" value=". lib/${project.manifest.classpath}" />

</manifest>

</jar>

</target>

>jar -xf MyJar.jar lib

-->

<!-- To take out just the lib/ directory jars out to the same directory as this JAR use below command</project>

<?xml version="1.0"?>