分类维护-通过Java8 Stream API 获取商品三级分类数据

package com.zsy.gulimall.product.entity;
import com.baomidou.mybatisplus.annotation.*;
import java.io.Serializable;
import java.util.List;
import com.fasterxml.jackson.annotation.JsonInclude;
import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
import lombok.Data;
import lombok.EqualsAndHashCode;
/**
 * <p>
 * 商品三级分类
 * </p>
 *
 * @author liulq
 * @since 2022-03-19
 */
@Data
@TableName("pms_category")
@EqualsAndHashCode(callSuper = false)
@ApiModel(value="PmsCategory对象", description="商品三级分类")
public class PmsCategory implements Serializable {
    private static final long serialVersionUID = 1L;
    @ApiModelProperty(value = "分类id")
    @TableId(value = "cat_id", type = IdType.AUTO)
    private Long catId;
    @ApiModelProperty(value = "分类名称")
    private String name;
    @ApiModelProperty(value = "父分类id")
    private Long parentCid;
    @ApiModelProperty(value = "层级")
    private Integer catLevel;
    @ApiModelProperty(value = "是否显示[0-不显示，1显示]")
    @TableLogic(value = "1", delval = "0")
    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 Integer productCount;
    @JsonInclude(JsonInclude.Include.NON_EMPTY)
    @TableField(exist = false)
    private List<PmsCategory> children;
}

实现

public List<CategoryEntity> listWithTree() {
    //1、查出所有分类
    List<CategoryEntity> entities = baseMapper.selectList(null);
    //2、组装成父子的树形结构
    //2.1）、找到所有的一级分类，给children设置子分类
    return entities.stream()
        // 过滤找出一级分类
        .filter(categoryEntity -> categoryEntity.getParentCid() == 0)
        // 处理，给一级菜单递归设置子菜单
        .peek(menu -> menu.setChildren(getChildless(menu, entities)))
        // 按sort属性排序
        .sorted(Comparator.comparingInt(menu -> (menu.getSort() == null ? 0 : menu.getSort())))
        .collect(Collectors.toList());
}
/**
 * 递归查找所有菜单的子菜单
 */
private List<CategoryEntity> getChildless(CategoryEntity root, List<CategoryEntity> all) {
    return all.stream()
        .filter(categoryEntity -> categoryEntity.getParentCid().equals(root.getCatId()))
        .peek(categoryEntity -> {
            // 找到子菜单
            categoryEntity.setChildren(getChildless(categoryEntity, all));
        })
        .sorted(Comparator.comparingInt(menu -> (menu.getSort() == null ? 0 : menu.getSort())))
        .collect(Collectors.toList());
}

效果