Vue ElementUI implements asynchronous loading tree

import List from '@/components/list.vue'
import Add from '@/components/add.vue'
import Tree from '@/components/tree.vue'
import AsynTree from '@/components/asyntree.vue'

export default{
    routes:[
        {path:"/list",component:List},
        {path:"/add",component:Add},
        {path:"/add/:id",component:Add},
        {path:"/tree",component:Tree},
        {path:"/asyntree",component:AsynTree}
    ]

}

<template>
  <div id="app">
    <router-link to="/add">Add</router-link>&nbsp;&nbsp;
    <router-link to="/list">List</router-link>&nbsp;&nbsp;
    <router-link to="/tree">Tree structure</router-link>&nbsp;&nbsp;
    <router-link to="/asyntree">Asynchronous tree structure</router-link>&nbsp;&nbsp;
    <router-view></router-view>
  </div>
</template>

<script>
import List from './components/list.vue'

export default {
  name: 'app',
  components:
    List
  }
}
</script>

<style>
#app {
  font-family: 'Avenir', Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
  margin-top: 60px;
}
</style>

<template>


<el-container>
  <el-aside width="200px">
    <el-tree ref="tree"
    :data="data"
    lazy
    show-checkbox
    node-key="id"
    check-strictly
    :load="loadnode"
    :props="defaultProps"
    @node-click="nodeclick">
    </el-tree>
  </el-aside>
  <el-main>

    <el-form :model="typeinfo" class="demo-form-inline">
    <el-form-item label="ID">
        <el-input v-model="typeinfo.id" readonly></el-input>
    </el-form-item>
    <el-form-item label="Category Name">
        <el-input v-model="typeinfo.label" placeholder="category name"></el-input>
    </el-form-item>
    <el-form-item label="Serial number">
        <el-input v-model="typeinfo.seqno" placeholder="Serial number"></el-input>
    </el-form-item>
   <el-form-item label="Parent ID">
        <el-input v-model="typeinfo.pid" readonly></el-input>
    </el-form-item>
    <el-form-item>
        <el-button type="primary" @click="dosave">Save</el-button>
        <el-button type="primary" @click="dochildsave">Add node</el-button>
    </el-form-item>
    </el-form>

  </el-main>
</el-container>

</template>

<script>
import axios from 'axios'

export default {
    data() {
        return {
            data:[], //Tree object data model defaultProps: { //Tree object property correspondence children: 'children',
                label: 'label'
            },
            typeinfo: {//Product classification entity object id:'',
                pid:'',
                label: '',
                seqno: ''
            }
        }
    },
    methods: {
        loadnode(node,resolve){
            //If you expand the first-level node, load the first-level node list from the background if (node.level==0)
            {
                this.loadfirstnode(resolve);
            }
            //If you expand other level nodes, dynamically load the next level node list from the background if (node.level>=1)
            {
                this.loadchildnode(node,resolve);
            }
        },
        //Load the first level node loadfirstnode(resolve){
            axios.get('http://localhost:6060/loadtype')
                .then(function(resp){
                    resolve(resp.data);
                })
        },
        //Refresh tree component refreshtree(){
            var _this = this;
            axios.get('http://localhost:6060/loadtype')
                .then(function(resp){
                    _this.data = resp.data;
                })
        },
        //Load the node's child node collection loadchildnode(node,resolve){
            axios.get('http://localhost:6060/loadtypechild?pid='+node.data.id)
                .then(function(resp){
                    resolve(resp.data);
                })
        },
        //Click the event triggered on the node, pass three parameters, the data object uses the first parameter nodeclick(data,dataObj,self)
        {
            //alert(data.label+",id="+data.id);
            this.typeinfo.id=data.id;
            this.typeinfo.pid=data.pid;
            this.typeinfo.label=data.label;
            this.typeinfo.seqno=data.seqno;
        },
        //Save classification method dosave()
        {
            var _this = this;
             axios.post('http://localhost:6060/savetype',this.typeinfo)
                .then(function(resp){
                    if(resp.data)
                        _this.refreshtree();
                })
        },
        //Save subclassification method dochildsave()
        {
            //Judge whether a node is selected in the left tree componentvar cnt=this.$refs['tree'].getCheckedNodes().length;
            if(cnt!=1)
            {
                this.$message('You must select a unique parent node');
                return;
            }
            //Get the tree object through this.$refs['tree'], where tree is the ref attribute of the tree component var dataObj = this.$refs['tree'].getCheckedNodes()[0];
    
            this.typeinfo.id='';
            this.typeinfo.pid=dataObj.id;
            var _this = this;
            axios.post('http://localhost:6060/savetype',this.typeinfo)
                .then(function(resp){
                    if(resp.data)
                        _this.refreshtree();
                })
        }
    }

}
</script>

@RequestMapping("/loadtype")
 @ResponseBody
 public List<TypeInfo> getTypeJson()
 {
  List<TypeInfo> rtn = getFirstNode();
  
  return rtn;
 }
  
 @RequestMapping("/loadtypechild")
 @ResponseBody
 public List<TypeInfo> getTypeByPid(Integer pid)
 {
  System.out.println("pid==="+pid);
  List<TypeInfo> rtn = addsrv.getTypeList(pid);
  
  return rtn;
 }
 
 private List<TypeInfo> getFirstNode()
 {
  TypeInfo root = addsrv.getRootType();
  List<TypeInfo> firstList = addsrv.getTypeList(root.getId());
  for(TypeInfo ti:firstList)
   recurseNode(ti);
  return firstList;
 }
 
 private void recurseNode(TypeInfo ti)
 {
  List<TypeInfo> children = addsrv.getTypeList(ti.getId());
  System.out.println("ti.id"+ti.getId()+",children="+children);
  if (children == null || children.size() == 0)
   return;
  ti.setChildren(children);
  for(TypeInfo chd:children)
  {
   recurseNode(chd);
  }
 }
 
 @RequestMapping("/savetype")
 @ResponseBody
 public Boolean savetype(@RequestBody TypeInfo ti)
 {
  try {
   Integer id = ti.getId();
   if(id != null)
    addsrv.updateType(ti);
   else {
    addsrv.saveType(ti);
   }
   return true;
  } catch (Exception e) {
   return false;
  }
  
 }