很多时候我们在前段展现时要用到多级菜单，刚好今天做了个简单的，整理一下；

首先我们要确定要展现的菜单结构：

--根菜单

--一级菜单A

--二级菜单A

--三级菜单A

--一级菜单B

与Hibernate构造无限极菜单不同的是，这个菜单传到前端时已经构造好，不是类似AJAX请求动态生成菜单；

好了 直奔主题：

import java.util.ArrayList;

import java.util.HashMap;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

public class MenuTest {

/**

* @param args

*/

public static void main(String[] args) {

MenuTest menuTest = new MenuTest();

List menuList = initMenu();//初始化菜单

Map menuMap = menuTest.rebuildMenus(menuList);//重构菜单

menuTest.showMenu(menuMap);//打印菜单

}

/**

* 重构菜单，构造成需要的结构

* @param menuList

* @return

*/

private Map rebuildMenus(List menuList) {

List rootMenuList=new ArrayList();//这个List用来存放根菜单

for (int j = 0; j < menuList.size(); j++) {

Map menu = (Map) menuList.get(j);

String parentId = menu.get("parentId").toString();

if (null==parentId || "".equals(parentId)) {

rootMenuList.add(menu);

}

}

menuList.removeAll(rootMenuList);//将根菜单从menuList中除去

HashMap menuMap = new HashMap();

for (int j = 0; j < rootMenuList.size(); j++) {//遍历根菜单，每一个跟菜单都遍历到最后一个子菜单(叶子节点)

Map menu = (Map) rootMenuList.get(j);

menu = this.pase(menu, menuList);

menuMap.put(menu.get("id"), menu);

}

return menuMap;

}

/**

* 递归构造菜单Map

* @param menu

* @param menuList

* @return

*/

private Map pase(Map menu, List menuList) {

for (int j = 0; j < menuList.size(); j++) {

Map menu2 = (Map) menuList.get(j);

if (menu2.get("parentId").toString().equals(menu.get("id").toString())) {

if(menu.get("children") == null){

menu.put("children", new ArrayList());

}

((List)menu.get("children")).add(menu2);

pase(menu2, menuList);

}

}

return menu;

}

/**

* 打印菜单

* @param menuMap

*/

private void showMenu(Map menuMap){

Iterator it = menuMap.keySet().iterator();

while(it.hasNext()){

Map menu = (Map) menuMap.get(it.next());

System.out.println(menu.get("id")+"--"+menu.get("name"));

this.buildChildMenu(menu);

}

}

/**

* 构造子菜单

* @param menu

*/

private void buildChildMenu(Map menu){

List childList = (List) menu.get("children");

if(null!=childList){

for(int i=0;i

Map childMap = (Map) childList.get(i);

System.out.println(childMap.get("id")+"--"+childMap.get("name"));

this.buildChildMenu(childMap);

}

}

}

/**

* 初始化菜单，实际项目中这部分数据是从数据库中获取

* @return

*/

public static List initMenu(){

List menuList = new ArrayList();

Map menuMap = new HashMap();

menuMap.put("id", "0000");

menuMap.put("name", "根菜单");

menuMap.put("parentId","");//根菜单的父菜单为空

Map menuMap1 = new HashMap();

menuMap1.put("id", "1000");

menuMap1.put("name", "一级菜单A");

menuMap1.put("parentId","0000");

Map menuMap2 = new HashMap();

menuMap2.put("id", "2000");

menuMap2.put("name", "一级菜单B");

menuMap2.put("parentId","0000");

Map menuMap3 = new HashMap();

menuMap3.put("id", "1100");

menuMap3.put("name", "二级菜单A");

menuMap3.put("parentId","1000");

Map menuMap4 = new HashMap();

menuMap4.put("id", "1110");

menuMap4.put("name", "三级菜单A");

menuMap4.put("parentId","1100");

menuList.add(menuMap);

menuList.add(menuMap1);

menuList.add(menuMap2);

menuList.add(menuMap3);

menuList.add(menuMap4);

return menuList;

}

}