vue+element树组件 实现树懒加载的过程详解

 <template>
 <el-tree :props="props"
   :load="loadNode"
   lazy
   show-checkbox>
 </el-tree>
</template>

<script>
export default {
 data () {
 return {
  props: {
  label: 'name',
  children: 'zones',
  isLeaf: 'leaf',

  },
 };
 },
 methods: {
 loadNode (node, resolve) {
  //如果展开第一级节点，从后台加载一级节点列表
  if (node.level == 0) {
  this.loadfirstnode(resolve);
  }
  //如果展开其他级节点，动态从后台加载下一级节点列表
  if (node.level >= 1) {
  this.loadchildnode(node, resolve);
  }
 },
 //加载第一级节点
 loadfirstnode (resolve) {

  this.api({
  url: "/test/tree",
  method: "post",

  }).then(data => {
  console.log(data);
  //this.data = data.list;
  return resolve(data.list);

  })
 },
 //加载节点的子节点集合
 loadchildnode (node, resolve) {
  this.api({
  url: "/test/tree2",
  method: "post",
  params: {
   id: node.data.id
  }
  }).then(data => {
  console.log(data);
  //this.defaultProps.children = data.list;
  return resolve(data.list);

  })
 }

 }

}
</script>

 @PostMapping("/tree")
 public JSONObject tree( ) {return userService.tree();
 }

 @PostMapping("/tree2")
 public JSONObject tree(@RequestParam Map<String, Object> user) {return userService.tree2(user);
 }

 /**
  * 树
  */
 JSONObject tree();
 
 /**
  * 树
  */
 JSONObject tree2(Map<String, Object> user);

 @Override
 public JSONObject tree() {
  List<JSONObject> list=userDao.tree();
  System.out.println(list);
  return CommonUtil.successPage(list);
 }
 @Override
 public JSONObject tree2(Map<String, Object> user) {
  int codept=Integer.parseInt(user.get("id").toString()) ;
  List<JSONObject> list=userDao.tree2(codept);
  return CommonUtil.successPage(list);
 }

 /**
  * 树
  */
 List<JSONObject> tree();
 List<JSONObject> tree2(@Param("codept")int codept);

 <select id="tree" resultType="com.alibaba.fastjson.JSONObject">
  SELECT [id]
  ,[codept]
  ,[name]
 FROM [dbo].[Dept] WHERE codept ='0'
 </select>

 <select id="tree2" resultType="com.alibaba.fastjson.JSONObject">
  SELECT [id]
  ,[codept]
  ,[name]
 FROM [dbo].[Dept] WHERE codept =#{codept}
 </select>