最近尝试用extjs来展示树状菜单。着实花了一番功夫。树状菜单的菜单项需要动态加载，而目前版本的extjs中只支持JSON格式的数据。查了一些资 料，决定使用struts2的json-plugin。首先按照例子做了一个，但是结果就是不成功，界面上只出来了一个js中生成的root节点，不能加 载从后台生成的数据。研究后发现是数据格式有问题。使用json-plugin生成的数据格式如下：
{"cls":"folder","id":10,"leaf":false,"children":[{"cls":"file","id":11,"leaf":true,"children":null,"text":"S600"},{"cls":"file","id":12,"leaf":true,"children":null,"text":"SLK200"}],"text":"Benz"}而extjs需要的数据格式如下：
[{"cls":"folder","id":10,"leaf":false,"children":[{"cls":"file","id":11,"leaf":true,"children":null,"text":"S600"},{"cls":"file","id":12,"leaf":true,"children":null,"text":"SLK200"}],"text":"Benz"}]区别很小，就只相差最外面的两个方括号。但是少了这两个方括号，在json中，含义迥然不同，前者表示一个对象，而后者表示一个数组。而extjs中 tree的dataloader需要的数据必须是一个数组。而这样的数据格式是json-plugin自动生成的，无法改变。所以，我最后放弃了json -plugin，转而使用json-lib来解决这个问题。
1. 下载json-lib, http://json-lib.sourceforge.net/
2. lib目录下的jar文件清单：
commons-beanutils-1.7.0.jar
commons-collections-3.2.jar
commons-digester-1.6.jar
commons-lang-2.3.jar
commons-logging-1.1.jar
dom4j-1.6.1.jar
ezmorph-1.0.4.jar
freemarker-2.3.8.jar
javassist-3.8.1.jar
json-lib-2.2.1-jdk15.jar
log4j-1.2.13.jar
ognl-2.6.11.jar
struts2-core-2.0.11.jar
xml-apis-1.0.b2.jar
xwork-2.0.4.jar
首先配置web.xml
<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <filter> <filter-name>struts2</filter-name> <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>/*</url-pattern> </filter-mapping></web-app>
然后是struts.xml
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" "http://struts.apache.org/dtds/struts-2.0.dtd"> <struts> <constant name="struts.devMode" value="true"/> <constant name="struts.i18n.encoding" value="UTF-8"/> <package name="person" extends="struts-default"> <action name="menus" method="execute"> <result>/menu.jsp</result> </action> </package></struts>
3. 树的节点模型（省略了getter，setter)
public class Menu { private int id; private String text; private boolean leaf; private String cls; private List<Menu> children;}4. action
package com.lab;import java.util.ArrayList;import java.util.List;import net.sf.json.JSONArray;public class MenuAction { private String menuString; private List<Menu> menus; public String execute() { menus = new ArrayList<Menu>(); Menu benz = new Menu(); benz.setText("Benz"); benz.setCls("folder"); benz.setLeaf(false); benz.setId(10); menus.add(benz); List<Menu> benzList = new ArrayList<Menu>(); benz.setChildren(benzList); Menu menu; menu = new Menu(); menu.setText("S600"); menu.setCls("file"); menu.setLeaf(true); menu.setId(11); benzList.add(menu); menu = new Menu(); menu.setText("SLK200"); menu.setCls("file"); menu.setLeaf(true); menu.setId(12); benzList.add(menu); Menu bmw = new Menu(); bmw.setText("BMW"); bmw.setCls("folder"); bmw.setLeaf(false); bmw.setId(20); menus.add(bmw); List<Menu> bmwList = new ArrayList<Menu>(); bmw.setChildren(bmwList); menu = new Menu(); menu.setText("325i"); menu.setCls("file"); menu.setLeaf(true); menu.setId(21); bmwList.add(menu); menu = new Menu(); menu.setText("X5"); menu.setCls("file"); menu.setLeaf(true); menu.setId(22); bmwList.add(menu); JSONArray jsonObject = JSONArray.fromObject(menus); try { menuString = jsonObject.toString(); } catch (Exception e) { menuString = "ss"; } return "success"; } public String getMenuString() { return menuString; } public void setMenuString(String menuString) { this.menuString = menuString; }}5. menu.jsp
<%@ taglib prefix="s" uri="/struts-tags" %><s:property value="menuString" escape="false"/>
6. html页面和js
我使用的就是extjs的example中的reorder.html和reorder.js，更改了reorder.js中treeloader的dataurl： menus.action
<html><head><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><title>Reorder TreePanel</title><link rel="stylesheet" type="text/css" href="extjs/resources/css/ext-all.css" /> <!-- GC --> <!-- LIBS --> <script type="text/javascript" src="extjs/adapter/ext/ext-base.js"></script> <!-- ENDLIBS --> <script type="text/javascript" src="extjs/ext-all.js"></script><script type="text/javascript" src="reorder.js"></script><!-- Common Styles for the examples --><link rel="stylesheet" type="text/css" href="extjs/resources/css/example.css" /></head><body><script type="text/javascript" src="../examples.js"></script><!-- EXAMPLES --><h1>Drag and Drop ordering in a TreePanel</h1><p>This example shows basic drag and drop node moving in a tree. In this implementation there are no restrictions and anything can be dropped anywhere except appending to nodes marked leaf (the files). <br></p><p>Drag along the edge of the tree to trigger auto scrolling while performing a drag and drop.</p><p>In order to demonstrate drag and drop insertion points, sorting was <b>not</b> enabled.</p><p>The data for this tree is asynchronously loaded with a JSON TreeLoader.</p><p>The js is not minified so it is readable. See <a href="reorder.js">reorder.js</a>.</p><div id="tree-div" style="overflow:auto; height:300px;width:250px;border:1px solid #c3daf9;"></div></body></html>
js:
/* * Ext JS Library 2.0.1 * Copyright(c) 2006-2008, Ext JS, LLC. * [email protected] * * http://extjs.com/license */Ext.onReady(function(){ // shorthand var Tree = Ext.tree; var tree = new Tree.TreePanel({ el:'tree-div', autoScroll:true, animate:true, enableDD:true, containerScroll: true, loader: new Tree.TreeLoader({ dataUrl:'http://localhost:8080/lab/menus.action' }) }); // set the root node var root = new Tree.AsyncTreeNode({ text: 'Ext JS', draggable:false, id:'source' }); tree.setRootNode(root); // render the tree tree.render(); root.expand();});
7.解析为List数据
代码如下：
EXTJS中的json数据
var comboStore = new Ext.data.Store({ proxy: new Ext.data.HttpProxy({ url:'adminGroup', //这里是struts请求到action method:'POST' //请求方式 }), reader: new Ext.data.JsonReader({ //总记录数 totalProperty: 'results', //总记录数 root: 'items', //记录集合 id:'roleId' }, ['roleId','roleName'] //显示的两个字段 ) });
JSON数据内容
{"items":[{"password":"ahui","adminId":1,"role":{"roleName":"系统管理员","roleId":2,"sequence":"2","admin":null,"logoutMark":"否"},"adminName":"ahui","logout":"否"}, {"password":"xiao","adminId":2,"role":{"roleName":"系统管理员","roleId":2,"sequence":"2","admin":null,"logoutMark":"否"},"adminName":"xiao","logout":"是"},"results":13}
下面是struts2里面的action代码 里面封装了ExtHelper工具类，里面有转换xml和json两种格式
public String findAll() throws Exception{ HttpServletRequest request = ServletActionContext.getRequest(); HttpServletResponse response = ServletActionContext.getResponse(); List list = groupService.getGroup(); //调用service里面的方法，把所有的数据都查询出来 String json = ExtHelper.getJsonFromList(list);//把list转换为json格式的数据 response.setContentType("text/json;charset=UTF-8");//设置数据到前台显示的字符编码，如果不转会有乱码 response.getWriter().write(json); System.out.println(json); return null; } 解析json的方法有很多,所以是怎么方便怎么来,json自己的包里也可以进行转换,但如果项目中用的是Struts2,直接用Struts2提供的方法更方便。