10.业务功能实现---商品服务三级分类树形API

1.商品服务三级分类树形API

1. 实体类，添加属性

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

    // ...

    /**
     * 子分类数据
     */
    @TableField(exist = false)
    private List<CategoryEntity> children;
}

2. 对数据进行分类的方法，组成树形结构：

public List<CategoryEntity> getListToTree() {
    //1.获取所有分类数据
    List<CategoryEntity> categoryEntities = baseMapper.selectList(null);
    //2.组装成树形结构
    //2.1).先找到所有的一级分类,然后继续设置分类下的子分类,最后排序，归约
    List<CategoryEntity> firstLevelMenu = categoryEntities.stream()
        .filter(categoryEntity -> categoryEntity.getParentCid() == 0)
        .map((menu) -> {
	    menu.setChildren(getChildren(categoryEntities, menu));
	    return menu;
	})
	.sorted((menu1, menu2) -> {
	    return (menu1.getSort() == null ? 0 : menu1.getSort()) - (menu2.getSort() == null ? 0 : menu2.getSort());
	}).collect(Collectors.toList());
	return firstLevelMenu;
}

/**
 * 递归设置各级子菜单
 *
 * @param all  所有的分类数据
 * @param root 一级菜单
 * @return
 */
private List<CategoryEntity> getChildren(List<CategoryEntity> all, CategoryEntity root) {
    List<CategoryEntity> children = all.stream()
	.filter(categoryEntity -> categoryEntity.getParentCid() == root.getCatId())
	.map(categoryEntity -> {
	    //递归设置子菜单
	    categoryEntity.setChildren(getChildren(all, categoryEntity));
	    return categoryEntity;
	}).sorted((menu1, menu2) -> {
       	    return (menu1.getSort() == null ? 0 : menu1.getSort()) - (menu2.getSort() == null ? 0 : menu2.getSort());
        }).collect(Collectors.toList());
	return children;
}