后台菜单返回树结构

• 数据库model ```java public class Menu { @TableId(type = IdType.AUTO) private Integer id;

  @TableField(fill =FieldFill.INSERT) private Date addTime;

  @TableField(fill = FieldFill.INSERT_UPDATE) private Date modifyTime;

  @ApiModelProperty(value = “排序”) private Integer sort;

  @ApiModelProperty(value = “类型(0.按钮 1.菜单)”) private Integer type;

  @ApiModelProperty(value = “图标”) private String icon;

  @ApiModelProperty(value = “菜单URL”) private String url;

  @ApiModelProperty(value = “上级菜单ID 第一级为0”) private Integer parentId;

  @ApiModelProperty(value = “菜单/按钮名称”) private String menuName;

  @ApiModelProperty(value = “菜单状态(0.失效,1.有效)”) private Integer state;

  @ApiModelProperty(value = “菜单级别”) private Integer level;

}

返回model
```java
public class MenuVo {
    @ApiModelProperty(value = "菜单/按钮Id")
    private Integer menuId;
    @ApiModelProperty(value = "菜单/按钮名称")
    private String menuName;
    @ApiModelProperty(value = "类型(0.按钮 1.菜单)")
    private Integer type;
    @ApiModelProperty(value = "图标")
    private String icon;
    @ApiModelProperty(value = "菜单/按钮 URL")
    private String url;
    @ApiModelProperty(value = "排序")
    private Integer sort;
    @ApiModelProperty(value = "菜单级别")
    private Integer level;
    @ApiModelProperty(value = "上级菜单ID 第一级为0")
    private Integer parentId;
    @ApiModelProperty(value = "是否选中 0未选 1已选")
    private Integer selected;
    @ApiModelProperty(value = "下级菜单信息")
    private List<MenuVo> children;
}

数据处理

   //roleId 为角色Id，用来标注这个角色有没有选中这个菜单
  @Override
    public GenericResponse findAllMenu(Integer roleId) {
        Role role = roleMapper.selectById(roleId);
        String menuIds = role.getMenuIds();
        List<String> listmenuIds = Lists.newArrayList();
        if (StringUtils.isNotBlank(menuIds)) {
            listmenuIds = Arrays.asList(menuIds.split(",")).stream().map(s -> (s.trim())).collect(Collectors.toList());
        }
        //所有有效的菜单 1：有效的
        List<Menu> menuList = menuMapper.selectList(new LambdaQueryWrapper<Menu>().eq(Menu::getState, 1));
        List<MenuVo> collect = combingParam(menuList, listmenuIds);
        return GenericResponse.response(collect);
    }


    /** 
     * 参数整理
     * @author X-MD
     * @date 2020/12/31 0031
     * @param  menuList
     * @param  listmenuIds
     * @return List
     **/
    private List<MenuVo> combingParam(List<Menu> menuList,List<String> listmenuIds){
        List<MenuVo> listVo = Lists.newArrayList();
        if (CollectionUtils.isEmpty(menuList)) {
            return listVo;
        }
        //使用stream拷贝list
        List<MenuVo> voList = menuList.stream()
                .map(menu -> {
                    MenuVo menuVo = new MenuVo();
                    BeanUtils.copyProperties(menu, menuVo);
                    return menuVo.setMenuId(menu.getId());
                })
                .collect(Collectors.toList());

        //先将所有一级部门添加至rslist
        for (MenuVo menuVo : voList) {
            //如果父级为空，则为顶级部门
            if (menuVo.getParentId().equals(0)) {
                menuVo = listmenuIds.contains(String.valueOf(menuVo.getMenuId())) ? menuVo.setSelected(2) : menuVo.setSelected(1);
                listVo.add(menuVo);
            }
        }

        // 为父级部门设置子部门，getChild是递归调用的
        for (MenuVo menuVo : listVo) {
            //传入父级部门Id,以及所有查询结果
            menuVo.setChildren(getChild(menuVo.getMenuId(), voList, listmenuIds));
        }
        return listVo.stream().sorted(Comparator.comparing(MenuVo::getSort)).collect(Collectors.toList());
    }

    /**
     * 传进父级ID,查找其子部门
     *
     * @param id
     * @param depts
     * @return List<MenuVo>
     * @author X-MD
     * @date 2020/12/30 0030
     **/
    public List<MenuVo> getChild(Integer id, List<MenuVo> depts, List<String> listmenuIds) {
        List<MenuVo> childList = new ArrayList<>();
        for (MenuVo menuVo : depts) {
            // 遍历所有属于父级节点的子节点
            if (menuVo.getParentId() != 0 && menuVo.getParentId().equals(id)) {
                menuVo = listmenuIds.contains(String.valueOf(menuVo.getMenuId())) ? menuVo.setSelected(2) : menuVo.setSelected(1);
                childList.add(menuVo);
            }
        }
        List<MenuVo> collect = childList.stream().sorted(Comparator.comparing(MenuVo::getSort))
                .collect(Collectors.toList());
        //然后给所有子节点添加子节点
        for (MenuVo menuVo : collect) {
            // 遍历所有属于父级节点的子节点
            menuVo.setChildren(getChild(menuVo.getMenuId(), depts, listmenuIds));
        }
        // 递归退出条件
        if (CollectionUtils.isEmpty(childList)) {
            return Lists.newArrayList();
        }
        return childList;
    }