教你如何使用Java8实现菜单树形数据

CREATE TABLE `pms_cateGory`  (
  `cat_id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '分类id',
  `name` char(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '分类名称',
  `parent_cid` bigint(20) NULL DEFAULT NULL COMMENT '父分类id',
  `cat_level` int(11) NULL DEFAULT NULL COMMENT '层级',
  `show_status` tinyint(4) NULL DEFAULT NULL COMMENT '是否显示[0-不显示，1显示]',
  `sort` int(11) NULL DEFAULT NULL COMMENT '排序',
  `icon` char(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '图标地址',
  `product_unit` char(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '计量单位',
  `product_count` int(11) NULL DEFAULT NULL COMMENT '商品数量',
  PRIMARY KEY (`cat_id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 1433 CHARACTER SET = utf8 COLLATE = utf8_general_ci COMMENT = '商品三级分类' ROW_FORMAT = Dynamic;

@Data
@TableName("pms_category")
public class CategoryEntity implements Serializable {
	private static final long serialVersionUID = 1L;

	
	@TableId
	private Long catId;
	
	private String name;
	
	private Long parentCid;
	
	private Integer catLevel;
	
	private Integer showStatus;
	
	private Integer sort;
	
	private String icon;
	
	private String productUnit;
	
	private Integer productCount;

	
	@TableField(exist = false)
	private List<CategoryEntity> children;

}

public List<CategoryEntity> listWithTree() {
        //1.查询所有分类
        List<CategoryEntity> entities = baseMapper.selectList(null);
        //2.组装
        //2.1) 所到所有的一级类别 ,parentId = 0
        List<CategoryEntity> levelOneMenus = entities.stream()
                .filter(item ->  item.getParentCid() == 0)
                .map(item -> {
                    item.setChildren(this.getChildrens(item, entities));
                    return item;
                })
                .sorted((item1, item2) -> {
                    return (item1.getSort() == null ? 0 : item1.getSort())  - (item2.getSort() == null ? 0 : item2.getSort());
                })
                .collect(Collectors.toList());
        return levelOneMenus;
    }

private List<CategoryEntity> getChildrens(CategoryEntity root, List<CategoryEntity> all){
        List<CategoryEntity> treeMenus = all.stream()
                //如果菜单中的父菜单Id == 当前菜单的id，则说明是子菜单
                .filter(item ->  Objects.equals(item.getParentCid(), root.getCatId()))
                .map(item -> {
                    //递归添加子菜单
                    List<CategoryEntity> childrens = getChildrens(item, all);
                    item.setChildren(childrens);
                    return item;
                })
                //排序
                .sorted((item1, item2) -> {
                    return (item1.getSort() == null ? 0 : item1.getSort())  - (item2.getSort() == null ? 0 : item2.getSort());
                })
                .collect(Collectors.toList());
        return treeMenus;
    }