code: public static Dao ext(Dao dao, FieldFilter filter, Object tableName) {
          if (tableName == null && filter == null)
              return dao;
          ExtDaoInvocationHandler handler = new ExtDaoInvocationHandler(dao, filter, tableName);
          return (Dao) Proxy.newProxyInstance(dao.getClass().getClassLoader(), iz, handler);
      }
docs: 同时进行字段过滤和动态表名封装
  
  @param dao
  Dao实例
  @param filter
  字段过滤
  @param tableName
  动态表名参数
  @return 封装好的Dao实例