使用easyui显示数据时，日期类型显示的object Object??

后台代码：

Map map = new HashMap();
 map.put("tableName", "engage_major_release");
 map.put("fields", "*");
map.put("orderField", "mre_id");
 map.put("sqlwhere", "");
 map.put("pageSize", 2);
 map.put("pageIndex", 1);
 map.put("orderType", 0);

List> list = this.zpBiz.queryEngage(map);
 JsonConfig config = new JsonConfig();
 //提供对实体中sql.Date的格式处理
config.registerJsonValueProcessor(java.sql.Date.class, new DateValueProcessor());

JSONArray json = JSONArray.fromObject(list,config);
 System.out.println(json);
 System.out.println(list.get(0).get("regist_time"));

response.setContentType("text/json;charset=UTF-8");
 PrintWriter outPrintWriter = response.getWriter();

outPrintWriter.print(json);
 outPrintWriter.close();
 return null;