public List<MenuDTO> getMenus() {
        List<MenuEntity> menuEntityList = list();
        if (CollectionUtils.isEmpty(menuEntityList)) {
            return Collections.emptyList();
        }
        List<MenuDTO> menuDTOList = BeanUtils.copyProperties(menuEntityList, MenuDTO.class);
        List<MenuDTO> resultDTOs = menuDTOList.stream()
                .filter(m -> m.getParentId() == 0)
                .peek(m -> m.setChildrenMenuDTOs(getChildMenus(m, menuDTOList)))
                .sorted(Comparator.comparing(MenuDTO::getSort))
                .collect(Collectors.toList());
        return resultDTOs;
    }

    private List<MenuDTO> getChildMenus(MenuDTO menuDTO, List<MenuDTO> menuDTOList) {
        return menuDTOList.stream()
                .filter(m -> Objects.equals(m.getParentId(), menuDTO.getId()))
                .peek(m -> m.setChildrenMenuDTOs(getChildMenus(m, menuDTOList)))
                .sorted(Comparator.comparing(MenuDTO::getSort))
                .collect(Collectors.toList());
    }

• MenuDTO

@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class MenuDTO {
    @ApiModelProperty("菜單id")
    private Long id;
    @ApiModelProperty("菜單名稱")
    private String name;
    @ApiModelProperty("菜單路徑")
    private String url;
    @ApiModelProperty("菜單圖標")
    private String icon;
    @ApiModelProperty("前端菜單索引")
    private String frontIndex;
    @ApiModelProperty("排序")
    private Integer sort;
    @ApiModelProperty("父級ID")
    private Long parentId;
    @ApiModelProperty("子菜單")
    private List<MenuDTO> childrenMenuDTOs;
}

DDDD