private int id; //id
 private String dept_name; //部門名稱
 private int pid; //上級部門id
 private int sort_num; //排序值
 private int create_id; //創建人
 private String create_time; //創建時間
 private int modify_id; //修改人
 private String modify_time; //最后修改時間
 private int is_del; // 是否刪除 0 未刪除 1 已刪除
 private int status; //status
 private String remark; //remark
 private List<Dept> deptChild = new ArrayList<>(); //部門迭代

List<Dept> selectDeptForJsonMenu();

<resultMap type="com.ys.entity.Dept" id="deptFirst">
 <result column="id" property="id" javaType="java.lang.Integer" />
 <result column="dept_name" property="dept_name" javaType="java.lang.String" />
 <result column="sort_num" property="sort_num" javaType="java.lang.Integer" />
 <result column="create_time" property="create_time" javaType="java.lang.String" />
 <result column="modify_id" property="modify_id" javaType="java.lang.Integer" />
 <result column="modify_time" property="modify_time" javaType="java.lang.String" />
 <result column="is_del" property="is_del" javaType="java.lang.Integer" />
 <result column="status" property="status" javaType="java.lang.Integer" />
 <result column="remark" property="remark" javaType="java.lang.String" />
 <collection column="id" property="deptChild" javaType="java.util.ArrayList" select="selectDeptForJsonMenuChild"/>
 </resultMap>
 <!-- 查詢部門菜單樹 -->
 <select id="selectDeptForJsonMenu" resultMap="deptFirst">
 SELECT * FROM sys_dept WHERE pid = 0 AND is_del = 0 ORDER BY sort_num
 </select>
 <select id="selectDeptForJsonMenuChild" resultMap="deptFirst" parameterType="java.lang.Integer">
 select * FROM sys_dept where pid = #{id} AND is_del = 0 ORDER BY sort_num
 </select>

public List<Dept> selectDeptForJsonMenu(){
 return mapper.selectDeptForJsonMenu();
 }

@RequestMapping(value = "selectDeptForJsonMenu",method={RequestMethod.GET,RequestMethod.POST})
 @ResponseBody
 public List<Dept> selectDeptForJsonMenu(){
 return service.selectDeptForJsonMenu();
 }

<div id="leftMenu">
</div>

$(function(){
 $.ajax({
 method:'post',
 url:getPath+"dept/selectDeptForJsonMenu",
 dataType:'json',
 success:function(data){
 if(data.length > 0){
 var showlist = $('<ul class="layui-nav layui-nav-tree"></ul>');
 showall(data, showlist);
 $("#leftMenu").html(showlist);
 }else{ 
 $('#leftMenu').html('<span class="layui-btn layui-btn-primary" id="add">添加</span>') ; 
 }
 }
 });
 //json為json數據
 //parent為最終html拼接內容
 function showall(json, parent) {
 for (var i in json) {
 //有子節點 遍歷
 if (json[i].deptChild.length > 0) {
 //創建li
 var li = $('<li class="layui-nav-item layui-nav-itemed"></li>');
 $(li).append('<a href="javascript:;" rel="external nofollow" rel="external nofollow" >'+json[i].dept_name+'</a>');
 $(li).append('<ul class="layui-nav-child"></ul>').appendTo(parent);
 //將UL選中 回調
 showall(json[i].deptChild, $(li).children().eq(1));
 }
 //無子級
 else {
 $('<li></li>').append('<a href="javascript:;" rel="external nofollow" rel="external nofollow" >'+json[i].dept_name+'</a>').appendTo(parent);
 }
 }
 }
});