Packages in separate Jars causes classpath error

Question

For the purposes of easy-updating and allowing developers to work on one part of a system without interfering with others, I have created separate Jar files for the main packages in my application. So;
com.me.pack1 is in Pack1.jar
com.me.pack2 is in Pack2.jar
An ant build takes care of building and packaging these up. The Jar files have the correct directory structure i.e.;
jar $ $JAVA_HOME/bin/jar tf /users/jmcparla/jar/Pack1.jar
META-INF/
META-INF/MANIFEST.MF
com/
com/me/
com/me/pack1/
com/me/pack1/MainClass.class
jar $ $JAVA_HOME/bin/jar tf /users/jmcparla/jar/Pack2.jar
META-INF/
META-INF/MANIFEST.MF
com/
com/me/
com/me/pack2/
com/me/pack2/OtherClass.classHowever when I run it;
jar $ $JAVA_HOME/bin/java -cp /users/jmcparla/jar/Pack2.jar -jar /users/jmcparla/jar/Pack1.jar
Entered main
Created MainClass instance
Exception in thread "main" java.lang.NoClassDefFoundError: com/me/pack2/OtherClass
        at com.me.pack1.MainClass.main(MainClass.java:13)The classes are;
MainClass.java
package com.me.pack1;
import com.me.pack2.OtherClass;
public class MainClass
    public static void main(String[] args)
        System.out.println("Entered main");
        new MainClass();
        System.out.println("Created MainClass instance");
        new OtherClass();
        System.out.println("Created OtherClass instance");
}OtherClass.java
package com.me.pack2;
public class OtherClass
}and the build file is;
build.xml
<project name="JarProblem" default="buildJars" basedir=".">
  <property name="classdir" value="classes"/>
  <target name="compile" depends="clean" description="compile the code">
      <mkdir dir="${classdir}"/>
      <javac debug="on" debuglevel="vars,lines,source" srcdir="."
             destdir="${classdir}" encoding="ISO-8859-1">
      </javac>
  </target>
  <target name="buildJars" depends="compile" description="build the jar files">
    <antcall target="buildPack2"/>
    <antcall target="buildPack1"/>
  </target>
  <target name="buildPack2" description="build the Pack2 jar">
    <tstamp>
      <format property="time" pattern="hh:mm aa dd/MM/yyyy"/>
    </tstamp>
    <jar destfile="Pack2.jar" update="false">
      <fileset dir="${classdir}">
        <!-- Only include the package we're building -->
        <include name="com/me/pack2/*"/>
      </fileset>
      <manifest>
        <attribute name="Built" value="${time}"/>
      </manifest>
    </jar>
  </target>
   <target name="buildPack1" description="build the Pack1 jar">
    <tstamp>
      <format property="time" pattern="hh:mm aa dd/MM/yyyy"/>
    </tstamp>
    <jar destfile="Pack1.jar" update="false">
      <fileset dir="${classdir}">
        <!-- Only include the package we're building -->
        <include name="com/me/pack1/*"/>
      </fileset>
      <manifest>
        <attribute name="Main-Class" value="com.me.pack1.MainClass"/>
        <attribute name="Built" value="${time}"/>
      </manifest>
    </jar>
  </target>
  <target name="clean" description="clean up the compiled source files">
    <delete verbose="false" failonerror="false">
      <fileset dir="${classdir}"/>
    </delete>
  </target>
</project>The build completes with no problems. So why can't the java command see OtherClass?

Answer 1

johnmcparlald wrote:
However when I run it;
jar $ $JAVA_HOME/bin/java -cp /users/jmcparla/jar/Pack2.jar -jar /users/jmcparla/jar/Pack1.jar
Entered main
Created MainClass instance
Exception in thread "main" java.lang.NoClassDefFoundError: com/me/pack2/OtherClass
at com.me.pack1.MainClass.main(MainClass.java:13)
I can't help you with ant but I can tell you that the command you entered looks wrong. If you use the -jar option with the java command, the only classpath that is used is the one specified by the Class-Path entry in the manifest - other classpaths are ignored.
So you either need to leave off the -jar, include the Pack1.jar file and specify the main class, or include the Class-Path: Pack2.jar entry in the manifest. (At least, it looks to me like there is no Class-Path in the manifest.)