blog_mapping.xml

<?xml version="1.0" encoding="UTF-8"?>
<castor:mapping>
  <castor:class name="test.Plgen">
    <castor:map-to xml="plgen" />
    <castor:field name="playlist" type="test.Playlist" collection="arraylist">
      <castor:bind-xml name="playlist" />
    </castor:field>
  </castor:class>

  <castor:class name="test.Playlist">
    <castor:field name="extensionType" type="string">
      <castor:bind-xml name="extensionType" />
    </castor:field>
  </castor:class>
</castor:mapping>