ArrayList 和Object的转换

   后台业务
           public ArrayList  getSelect(){
commandContext.clear();
commandContext.setCommandName("getSystemCommonVOs");
commandContext.setServiceName("systemCommonService");
SystemCommonVO vo = new SystemCommonVO();
vo.setField("*");
vo.setTablename("T_Util");
commandContext.setCommandParams(new Object [] {vo}, new Class [] {SystemCommonVO.class});
ArrayList rs =(ArrayList)this.executeCommandContext().getResult();
return rs;
}
   前台js和页面
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'MyJsp' starting page</title>
    <script type="text/javascript" src="<%=request.getContextPath()%>/dwr/engine.js"></script>
<script type="text/javascript" src="<%=request.getContextPath()%>/dwr/util.js"></script>
<script type="text/javascript" src="<%=request.getContextPath()%>/dwr/interface/showall.js"></script>
<script type="text/javascript">
  function setProValue(){
  showall.getSelect(callback);
}
  function callback(data) {
      DWRUtil.addOptions("conId", data,data.U_Name);
 
  }
  
</script>
  </head>
  <body>
<select id="conId" name="controy" >
</select>
  <button  type="submit" onclick="setProValue()"></button>
  
  </body>
</html>  每次运行下拉列表都是显示的 object Object    求大神开导。