@Override
 public boolean onCreate(String eventsXmlString) {
   this.doc = XmlUtil.getDocumentByString(eventsXmlString);
   if (doc == null) {
     throw new IllegalArgumentException("Blank XML content or format erro:" + eventsXmlString);
   }
   return true;
 }
 public DemoXmlUpdateEventDatabase(String eventXml) {
   this.doc = XmlUtil.getDocument(eventXml);
 }