dom4j学习笔记：动态创建和修改Spring的bean配置文件
今天本来打算写Spring温故知新系列的第二篇，不过突然想起一直都忘了学怎么用java来操作XML，这么重要的事情居然拖了这么久才想起来实在是太不应该了，于是今天就先练习一下用dom4j来操作XML。
其实dom4j这个库实在是太方便了，使用起来跟C#操作XML几乎没太大差别，也没什么难度，所以就先贴两段代码吧。
其中有几个要点：
1、如果只是创建一个XML文件，那么只需要导入dom4j-1.6.1.jar就可以了，路径如下：
spring-framework-2.5.6\lib\dom4j\dom4j-1.6.1.jar
如果是需要读取或者修改，那么就需要导入这个库内的另外一个文件：
spring-framework-2.5.6\lib\dom4j\jaxen-1.1-beta-7.jar
否则就会报错，报错内容如下：
java.lang.NoClassDefFoundError: org/jaxen/JaxenException
...
...
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2、dom4j是支持链式操作的，这跟jQuery非常像。这样一来创建一个XML文件就非常方便而且代码结构看起来也更加清晰明了。
3、要学会XPath.... 要不然你会很痛苦，不过XPath其实很简单，应该花不了多少时间，难不住各位的，哈哈~
Action部分：
package com.iteye.bolide74.action;import java.io.File;import java.io.FileWriter;import java.io.IOException;import java.util.List;import org.dom4j.Document;import org.dom4j.DocumentException;import org.dom4j.DocumentHelper;import org.dom4j.Element;import org.dom4j.Node;import org.dom4j.io.SAXReader;import org.dom4j.io.XMLWriter;public class MyDom4j {/** * 动态创建一个bean配置文件，包含HelloWorld这个bean，并添加初始值 * */public void createXML(String xmlPath, String msg) throws IOException {Document XmlDoc = DocumentHelper.createDocument();XmlDoc.addDocType("beans", "-//SPRING//DTD BEAN//EN","http://www.springframework.org/dtd/spring-beans.dtd");//首先创建beans根节点Element beansEle = XmlDoc.addElement("beans");//注意：dom4j是支持类似于jQuery一样的链式操作的Element beanHelloWorld = beansEle.addElement("bean").addAttribute("id", "HelloWorld").addAttribute("class", "com.iteye.bolide74.action.HelloWorld");Element propertyHelloWorld = beanHelloWorld.addElement("property").addAttribute("name", "msg");Element valueHelloWorld = propertyHelloWorld.addElement("value").addText(msg);XMLWriter outXml = new XMLWriter(new FileWriter(new File(xmlPath)));outXml.write(XmlDoc);outXml.close();}/** * 首先遍历一个bean配置文件里的所有bean，获取id和class的值， 然后修改HelloWorld这个bean的msg的值 * @throws IOException * */public void editXML(String xmlPath, String msg) throws DocumentException, IOException {Document XmlDoc = new SAXReader().read(new File(xmlPath));List<Element> xmlList = XmlDoc.selectNodes("/beans/bean");System.out.println("\r\n遍历所有的bean获得id和class：");for (Element element : xmlList) {System.out.println("id:" + element.attributeValue("id")+ " / class:" + element.attributeValue("class"));}System.out.println("\r\n动态修改HelloWorld这个bean的msg值：");//用XPath来获取单一节点Node valueHelloWorld = XmlDoc.selectSingleNode("/beans/bean[@id='HelloWorld']/property[@name='msg']/value");System.out.println("原始值为：" + valueHelloWorld.getText());valueHelloWorld.setText(msg);System.out.println("修改后的值为：" + valueHelloWorld.getText());//修改完了以后记得保存，要不然你会纳闷为什么XML文件没变的，哈哈XMLWriter outXml = new XMLWriter(new FileWriter(new File(xmlPath)));outXml.write(XmlDoc);outXml.close();}}package com.iteye.bolide74.action;public class HelloWorld {public String msg;public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}}package com.iteye.bolide74.tester;import java.io.IOException;import org.dom4j.DocumentException;import org.springframework.context.ApplicationContext;import org.springframework.context.support.FileSystemXmlApplicationContext;import com.iteye.bolide74.action.HelloWorld;import com.iteye.bolide74.action.MyDom4j;public class HelloWorldTester {public static void main(String[] args) {String xmlPath = "/WebContent/WEB-INF/conf/config_dom4j.xml";MyDom4j myBeans = new MyDom4j();try {myBeans.createXML(System.getProperty("user.dir") + xmlPath,"Hello,world!this is created by dom4j!");} catch (IOException e) {e.printStackTrace();}ApplicationContext ac = new FileSystemXmlApplicationContext(xmlPath);HelloWorld helloWorld = (HelloWorld) ac.getBean("HelloWorld");System.out.println(helloWorld.getMsg());try {myBeans.editXML(System.getProperty("user.dir") + xmlPath,"Hello,world!this is edited by dom4j!");} catch (DocumentException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}// 重新获取bean配置文件ac = new FileSystemXmlApplicationContext(xmlPath);helloWorld = (HelloWorld) ac.getBean("HelloWorld");System.out.println("\r\n" + helloWorld.getMsg());}}Hello,world!this is created by dom4j!遍历所有的bean获得id和class：id:HelloWorld / class:com.iteye.bolide74.action.HelloWorld动态修改HelloWorld这个bean的msg值：原始值为：Hello,world!this is created by dom4j!修改后的值为：Hello,world!this is edited by dom4j!Hello,world!this is edited by dom4j!