Yes you can specify a fileset. See these links:
http://ant.apache.org/manual/CoreTasks/jar.html or
http://ant.apache.org/manual/CoreTasks/war.html

However, typically I do a fresh ant build and then include everything
in the classes directory. In my make target I can fuss about which
classes and files to include and exclude. Here are my slightly edited
jar and make targets for another example apart from the ant manual.

<target name="jar" depends="init,clean,make">
   <delete file="${jar.dir}/myjar.jar" />
   <jar destfile="${jar.dir}/myjar.jar" basedir="./classes">
       <manifest>
          <attribute name="Built-By" value="${user.name}" />
          <attribute name="Main-Class" value="mypackage.MyMainClass"/>
          <attribute name="Class-Path" value="." />
       </manifest>
   </jar>
</target>

<target name="make" depends="init">
   <copy todir="${classes.dir}">
       <fileset dir="${source.dir}">
           <include name="**/*.properties" />
           <include name="**/*.gif" />
           <include name="**/*.jpg" />
           <include name="**/*.png" />
           <include name="**/*.txt" />
       </fileset>
   </copy>
   <javac destdir="${classes.dir}" optimize="off" debug="on"
           target="1.5" source="1.5">
       <src path="${source.dir}" />
       <exclude name="**/Test.java" />
       <compilerarg line="-Xlint" />
   </javac>
</target>

Cheers,

Dan Andrews
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Ansir Development Limited www.ansir.ca
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