树形结构的接口和前端代码

//一级分类
@Data
public class OneSubject {
    private String id;
    private String title;

    //一个一级分类有多个二级分类
    private List<TwoSubject> children = new ArrayList<>();
}


//二级分类
@Data
public class TwoSubject {
    private String id;
    private String title;
}

@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
@ApiModel(value="EduSubject对象", description="课程科目")
public class EduSubject implements Serializable {

    private static final long serialVersionUID = 1L;

    @ApiModelProperty(value = "课程类别ID")
    @TableId(value = "id", type = IdType.ID_WORKER_STR)
    private String id;

    @ApiModelProperty(value = "类别名称")
    private String title;

    @ApiModelProperty(value = "父ID")
    private String parentId;

    @ApiModelProperty(value = "排序字段")
    private Integer sort;

    @ApiModelProperty(value = "创建时间")
    @TableField(fill = FieldFill.INSERT)
    private Date gmtCreate;

    @ApiModelProperty(value = "更新时间")
    @TableField(fill = FieldFill.INSERT)
    private Date gmtModified;

}

@RestController
@RequestMapping("/eduservice/subject")
@CrossOrigin
public class EduSubjectController {


    @Autowired
    private EduSubjectService subjectService;


    //课程分类列表（树形）
    @GetMapping("getAllSubject")
    public R getAllSubject() {
        //list集合泛型是一级分类
        List<OneSubject> list = subjectService.getAllOneTwoSubject();
        return R.ok().data("list",list);
    }

}

@Service
public class EduSubjectServiceImpl extends ServiceImpl<EduSubjectMapper, EduSubject> implements EduSubjectService {

  
    @Override
    public List<OneSubject> getAllOneTwoSubject() {
        //1 查询所有一级分类  parentid = 0
        QueryWrapper<EduSubject> wrapperOne = new QueryWrapper<>();
        wrapperOne.eq("parent_id","0");
        List<EduSubject> oneSubjectList = baseMapper.selectList(wrapperOne);

        //2 查询所有二级分类  parentid != 0
        QueryWrapper<EduSubject> wrapperTwo = new QueryWrapper<>();
        wrapperTwo.ne("parent_id","0");
        List<EduSubject> twoSubjectList = baseMapper.selectList(wrapperTwo);

        //创建list集合，用于存储最终封装数据
        List<OneSubject> finalSubjectList = new ArrayList<>();

        //3 封装一级分类
        //查询出来所有的一级分类list集合遍历，得到每个一级分类对象，获取每个一级分类对象值，
        //封装到要求的list集合里面 List<OneSubject> finalSubjectList
        for (int i = 0; i < oneSubjectList.size(); i++) { //遍历oneSubjectList集合
            //得到oneSubjectList每个eduSubject对象
            EduSubject eduSubject = oneSubjectList.get(i);
            //把eduSubject里面值获取出来，放到OneSubject对象里面
            OneSubject oneSubject = new OneSubject();
//            oneSubject.setId(eduSubject.getId());
//            oneSubject.setTitle(eduSubject.getTitle());
            //eduSubject值复制到对应oneSubject对象里面
            BeanUtils.copyProperties(eduSubject,oneSubject);
            //多个OneSubject放到finalSubjectList里面
            finalSubjectList.add(oneSubject);

            //在一级分类循环遍历查询所有的二级分类
            //创建list集合封装每个一级分类的二级分类
            List<TwoSubject> twoFinalSubjectList = new ArrayList<>();
            //遍历二级分类list集合
            for (int m = 0; m < twoSubjectList.size(); m++) {
                //获取每个二级分类
                EduSubject tSubject = twoSubjectList.get(m);
                //判断二级分类parentid和一级分类id是否一样
                if(tSubject.getParentId().equals(eduSubject.getId())) {
                    //把tSubject值复制到TwoSubject里面，放到twoFinalSubjectList里面
                    TwoSubject twoSubject = new TwoSubject();
                    BeanUtils.copyProperties(tSubject,twoSubject);
                    twoFinalSubjectList.add(twoSubject);
                }
            }
            //把一级下面所有二级分类放到一级分类里面
            oneSubject.setChildren(twoFinalSubjectList);
        }
        return finalSubjectList;

    }
}

 {
    path: ‘/subject‘,
    component: Layout,
    redirect: ‘/subject/list‘,
    name: ‘课程分类管理‘,
    meta: { title: ‘课程分类管理‘, icon: ‘example‘ },
    children: [
      {
        path: ‘list‘,
        name: ‘课程分类列表‘,
        component: () => import(‘@/views/edu/subject/list‘),
        meta: { title: ‘课程分类列表‘, icon: ‘table‘ }
      },
      {
        path: ‘save‘,
        name: ‘添加课程分类‘,  
        component: () => import(‘@/views/edu/subject/save‘),
        meta: { title: ‘添加课程分类‘, icon: ‘tree‘ }
      }
    ]
  },

import request from ‘@/utils/request‘
export default {
    //1 课程分类列表
    getSubjectList() {
        return request({
            url: ‘/eduservice/subject/getAllSubject‘,
            method: ‘get‘
          })
    }
}

<template>
  <div class="app-container">
    <el-input v-model="filterText" placeholder="Filter keyword" style="margin-bottom:30px;" />

    <el-tree
      ref="tree2"
      :data="data2"
      :props="defaultProps"
      :filter-node-method="filterNode"
      class="filter-tree"
      default-expand-all
    />

  </div>
</template>

<script>
import subject from ‘@/api/edu/subject‘
export default {

  data() {
    return {
      filterText: ‘‘,
      data2: [],  //返回所有分类数据
      defaultProps: {
        children: ‘children‘,
        label: ‘title‘
      }
    }
  },
  created() {
      this.getAllSubjectList()
  },
  watch: {
    filterText(val) {
      this.$refs.tree2.filter(val)
    }
  },

  methods: {
    getAllSubjectList() {
        subject.getSubjectList()
            .then(response => {
                this.data2 = response.data.list
            })
    },
    filterNode(value, data) {
      if (!value) return true
      return data.title.toLowerCase().indexOf(value.toLowerCase()) !== -1
    }
  }
}
</script>