JAVA构造多级菜单

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<childList.size();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;
	}
	
	

}