Here is the commented example of the configuration file. The address of this file must be hardly-coded in the org.gnu.amSpacks.user.invoke, present as part of your package.

<?xml version="1.0" encoding="UTF-8"?>

<updates>
  <!-- sample configuration file for stableUpdate 1.0. All addresses are
  imaginary. -->

  <!-- specify the short announcement that will be displayed at the bottom
  of the update dialog. -->
  <announcement>
  The first test
  </announcement>

   <!-- this defines an update, upgrading from 1.1.1 to 1.1.2, 25000 bytes -->
  <update from="1.1.1" to="1.1.2" size="25000" checksup="asdfa12.asderwerew.2500">
   <!-- checksum added at stableUpdate 1.0.2 and will be verified after downloading -->

   <!-- Icons are displayed in the update dialog. -->
   <icon hyperlink="http://jsight.sourceforge.net/index_SF.htm"
    url="http://sourceforge.net/sflogo.php?group_id=72076&type=2"/>
     <!-- do not forget to use & instead of & in urls -->

   <!-- Release note for this update: -->
   <about>Be sincere!</about>

   <!-- url must point to the update archive. The address icons (not required) are displayed
        in the mirror list.  -->
   <address url="http://switch.dl/autoupdater.jar"
            icon="http://images.sourceforge.net/prdownloads/switch_100x34.gif"/>

   <address url="http://easynews.dl/autoupdater.jar"
           icon="http://images.sourceforge.net/prdownloads/easynews_100x34.jpg"/>

   <address url="http://optusnet.dl/autoupdater.jar"
            icon="http://images.sourceforge.net/prdownloads/optusnet_100x34.gif"/>
  </update>

  <!-- Another update -->
  <update from="1.1.0" to="1.1.1" size="95000">

   <address url="http://www.bioinformatics.org/uu1.jar" icon="ku.gif">Bioinformatics.org</address>
   <address url="http://www.sourceforge.net/uu2.jar" icon="kx.gif">RRR hypernet</address>
   <address url="http://uu.sourceforge.net/uu2.jar" icon="http://www.ku.gif"/>

  </update>

  <update from="1.1.3" to="1.1.2" size="1123124">
   <!-- Example of the address without an icon. -->
   <address url="http://www.lrytas.lt/uu3.jar"/>
  </update>

</updates>

As you see, for each update it is possible to provide several addresses. Host icon, if present, is displayed during download.