java实现多级菜单

在实现菜单查询目前遇到两种方式

1、根据父id依次查询该id为父id的同级菜单，一次查询一个（上下级菜单通过parentId进行关联）

    1.1、前台传入参数为父parentId（select  *  from category where parentId =#{parentId }）

   ①

@GetMapping("/list")
public ResponseEntity<List<Category>> queryCategoryByPid(@RequestParam("pid") Long pid) {
    return  ResponseEntity.ok().body(categoryService.list(pid));
}

②

@Override
public List<Category> list(Long pid) {
    final Category category = new Category();
    category.setParentId(pid);
    final List<Category> categories = categoryMapper.select(category);
    if (CollectionUtils.isEmpty(categories)) {
        throw new LyException(ExceptionEnum.CATEGORY_ISNULL);
    }
    return categories;
}

2、通过sql一次全部出来所有菜单

<select id="queryList" resultType="io.renren.modules.sys.entity.SysDeptEntity">

select t1.*,(select t2.name from sys_dept t2 where t2.dept_id=t1.parent_id)parentName from sys_dept t1 where

t1.del_flag = 0

<if test="sql_filter != null">

and ${sql_filter}

</if>

</select>