Cannot read property 'length' of undefine

前台js代码：
$(document).ready(function(){
var url = "teachers/getSchool.do";
$.ajax({
type: "POST",
url: url,
//async : false,
dataType:"text",
success : function(data) {
alert(data);
alert("8888");
var str="

";
console.log(data);
$.each(data.list,function (i, value) {

str=str+"

"+value[i].SCHOOLNAME+"

";

});
str = str+"

";
$(".erjimenu").html(str);
},
error:function(data){
console.log(data);
$("#form-notice").html('获取学校出错，请重新获取');
}
});
})
后台代码：
@RequestMapping(value="/getSchool")
@ResponseBody
public Object getSchool(HttpServletResponse response){

    PageData pd = new PageData();
    Map<String, Object> map = null;
    List<PageData> schoolList = null;
    try {
        pd = this.getPageData();
        pd.put("SYSNAME", Tools.readTxtFile(Const.SYSNAME)); //读取系统名称
        PageData rolePd = new PageData();
        rolePd.put("PARENT_ID", Const.PARENT_ROLES);
        map = new HashMap<String, Object>();
        schoolList = this.schoolService.listAll(new PageData());
        if (schoolList != null)
            pd.put("msg", "success");
        else
            pd.put("msg", "error");
        schoolList.add(pd);
        map.put("list", schoolList);
    } catch (Exception e) {
        // TODO: handle exception
    }
    return AppUtil.returnObject(pd, map);
}