java利用递归实现类别树示例代码

@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
@ApiModel("商品类别表")
public class OrdersCategory implements Serializable {

	private static final long serialVersionUID = 1L;

 @ApiModelProperty(value = "类别主键")
 @TableId(value = "id", type = IdType.ASSIGN_ID)
 private Integer catId;

 @ApiModelProperty(value = "分类名称")
 private String name;

 @ApiModelProperty(value = "父分类id")
 private Integer parentCid;

 @ApiModelProperty(value = "层级")
 private Integer catLevel;

 @ApiModelProperty(value = "是否显示[0-不显示，1显示]")
 private Integer showStatus;

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

 @ApiModelProperty(value = "图标地址")
 private String icon;

 @ApiModelProperty(value = "计量单位")
 private String productUnit;

 @ApiModelProperty(value = "商品数量")
 private String productCount;
}

@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
@ApiModel("商品类别返回对象")
public class OrdersCategoryVo extends OrdersCategory implements Serializable {

 private static final long serialVersionUID = 1L;

 @ApiModelProperty(value = "子类别树")
 List<OrdersCategoryVo> childrenCategoryList;
}

 /**
  * 获取商品类别树
  * @return
  */
 @Override
 public List<OrdersCategoryVo> getCategoryTree() {
  //查出分类表所有数据
  List<OrdersCategoryVo> entityList = categoryMapper.getCategoryTreeAll();
  //查询出所有的一级分类数据. 使用stream的api
  List<OrdersCategoryVo> firstEntityList = entityList.stream()
  	.filter(categoryVo -> categoryVo.getParentCid().intValue() == 0)
  	.map((menu) -> {
   //传递当前的商品分类, 和所有的分类,递归查询出每个一级分类下的子分类
   menu.setChildrenCategoryList( getChildrens(menu,entityList));
   return menu;
  } ).collect(Collectors.toList());
  return firstEntityList;
 }

 /**
  * 递归查询子父类
  * @param root 当前节点的父id
  * @param all 所有的商品分类
  * @return
  */
 private List<OrdersCategoryVo> getChildrens(OrdersCategoryVo root, List<OrdersCategoryVo> all) {
  List<OrdersCategoryVo> childrenList = all.stream()
  	.filter(categoryVo -> categoryVo.getParentCid().intValue() == root.getCatId().intValue())
  	.map(categoryVo -> {
   //子菜单可能还有子菜单, 因此递归查询 , 查询出子菜单
   categoryVo.setChildrenCategoryList(getChildrens(categoryVo, all));
   return categoryVo;
  }).collect(Collectors.toList());

  return childrenList;
 }

<template>
 <el-tree :data="data" :props="defaultProps" @node-click="handleNodeClick"></el-tree>
</template>

<script>
import { getCategoryTree } from '@/api/category'

export default {
 data() {
 return {
  data: [],
  defaultProps: {
   children: 'childrenCategoryList',
   label: 'name'
  }
 }
 },
 created() {
  this.getData();
 },
 methods: {
 handleNodeClick () {

 },
 getData() {
  getCategoryTree()
  .then(response => {
   this.data = response.data.data.list
  })
  .catch(() => {
   this.data = []
  })
 }
 }