springboot使用遞歸獲取導(dǎo)航無(wú)限級(jí)分類,使用thymeleaf渲染導(dǎo)航欄,在實(shí)際項(xiàng)目中經(jīng)常會(huì)出現(xiàn)三級(jí)分類或者多級(jí)分類的情況,一般采用存pid的方式存儲(chǔ),在去數(shù)據(jù)時(shí)遞歸迭代下數(shù)據(jù)就行來(lái)看看導(dǎo)航欄遞歸實(shí)現(xiàn)吧!
項(xiàng)目的源代碼:碼云下載
由于更新的數(shù)據(jù)庫(kù)字段和插入了部分?jǐn)?shù)據(jù),需要重新執(zhí)行下碼云的sql語(yǔ)句,同時(shí)重命名了文件夾mapper為dao.

1. 實(shí)體類增加children

public class Nav {
    private Integer id;

    private String title;

    private String url;

    private Integer sorts;

    private Integer pid;

    private Date createTime;

    private Date updateTime;

    private Boolean status;

    private List<Nav> children;

2. NavServiceImpl增加遞歸格式化分類函數(shù)unlimitedTree,格式成帶children層級(jí)

@Service
public class NavServiceImpl implements NavService {
    @Resource
    private NavDao navDao;
    @Override
    public int deleteByPrimaryKey(Integer id) {
        return 0;
    }

    @Override
    public int insert(Nav record) {
        return 0;
    }

    @Override
    public Nav selectByPrimaryKey(Integer id) {
        return null;
    }

    @Override
    public List<Nav> selectAll() {
        List<Nav> navs = navDao.selectAll();
        return unlimitedTree(navs, 0);
    }

    @Override
    public int updateByPrimaryKey(Nav record) {
        return 0;
    }

    public static List<Nav> formatNavs(List<Nav> navs,List<Nav> navs_list,Integer pid) {
        for (Nav nav:navs){
            navs_list.add(nav);
            List<Nav> childrenNavs=nav.getChildren();
            if(null!=childrenNavs){
                navs_list=formatNavs(childrenNavs,navs_list,nav.getPid());
            }
        }
        return navs_list;
    }
    public static List<Nav> unlimitedTree(List<Nav> navs,Integer pid) {
        ArrayList<Nav> navs_list =new ArrayList<>();
        for (Nav nav:navs){
            if(pid==nav.getPid()){
                nav.setChildren(unlimitedTree(navs,nav.getId()));
                navs_list.add(nav);
            }
        }
        return navs_list;
    }

}

3.IndexController查詢出值

@Controller
public class IndexController {
    @Resource
    private NavService nav;
    @GetMapping("/")
    public String index(Model m) {
        List<Nav> navs = nav.selectAll();
        m.addAttribute("navs",navs);
        return "index";
    }
}

4.使用thymeleaf渲染顯示數(shù)據(jù)

<nav>
  <ul id="starlist">
    <li><a href="index.html" title="首頁(yè)">網(wǎng)站首頁(yè)</a></li>
    <li th:each="nav : ${navs}" th:class="${not #lists.isEmpty(nav.children)}?'menu'">
      <a th:href="@{${nav.url}}" th:text="${nav.title}" href="index1.html">個(gè)人博客</a>
      <ul th:if="${not #lists.isEmpty(nav.children)}" class="sub">
        <li th:each="children : ${nav.children}">
         <a th:href="@{${children.url}}" th:text="${children.title}" href="index1.html">CSS3|Html5</a>
        </li>
      </ul>
     </li>
   </ul>
 </nav>

部分代碼未完全貼出來(lái),詳細(xì)代碼參考碼云倉(cāng)庫(kù)代碼!