x-requested-with是做什么用的？：区分是Ajax异步请求还是普通的同步请求
项目中最复杂的sql语句：
select g.id,g.name,m.id menu_id,m.name menu_name,m.url,m.parent_id,m.order_num,a.name action_name
,a.id action_id,a.url action_url,a.menu_id action_menu_id,a.method
from sys_group g
left join sys_group_menu gm on g.id = gm.group_id
left join sys_menu m on gm.menu_id = m.id
left join sys_group_action ga on g.id = ga.group_id
left join sys_action a on ga.action_id = a.id
where g.id = #{_parameter}
order by m.order_num
