实现三级菜单分类

在controller直接调用即可

这里使用的是mybatis plus

数据库表结构

@Service("categoryService")
public class CategoryServiceImpl extends ServiceImpl<CategoryDao, CategoryEntity> implements CategoryService {

    @Override
    public List<CategoryEntity> listWithTree() {
        // 1.查询出所有分类
        List<CategoryEntity> entities = baseMapper.selectList(null);

        // 2.组装成父子树形结构
        // 2.1找到所有一级分类
        List<CategoryEntity> levelMenus = entities.stream().filter((categoryEntity) -> {
            return categoryEntity.getParentCid() == 0;
        }).map((menu)->{
            menu.setChildren(getChildren(menu, entities));
            return menu;
        }).sorted((menu1, menu2)->{
            return (menu1.getSort()==null?0:menu1.getSort())-(menu2.getSort()==null?0:menu2.getSort());
        }).collect(Collectors.toList());
        return levelMenus;
    }

    /**
     * 递归查找所有菜单的子菜单
     * @param root
     * @param all
     * @return
     */
    private List<CategoryEntity> getChildren(CategoryEntity root, List<CategoryEntity> all) {
        List<CategoryEntity> children = all.stream().filter(categoryEntity -> {
            return categoryEntity.getParentCid() == root.getCatId();
        }).map(categoryEntity -> {
            // 1.找到子菜单
            categoryEntity.setChildren(getChildren(categoryEntity, all));
            return categoryEntity;
        }).sorted((menu1, menu2)->{
            // 2.菜单排序
            return (menu1.getSort()==null?0:menu1.getSort())-(menu2.getSort()==null?0:menu2.getSort());
        }).collect(Collectors.toList());
        return children;
    }

}