1. dom4j概述
解析DOM4J是一个开源XML解析包，采用了Java集合框架并完全支持DOM，SAX和JAXP。
最大的特色是使用了大量的接口，主要接口都在org.dom4j里定义。
2. dom4j的使用
2.1 Doucment相关用法
2.11 解析XML文件，获得Document对象
SAXReader reader = new SAXReader();
Document document = reader.read(new File("input.xml"));2.12 解析字符串，获得Document对象String text = "<members></members>"; Document document = DocumentHelper.parseText(text);2.13 无脑自建Document对象
Document document = DocumentHelper.createDocument();
Element root = document.addElement("members");// 创建根节点2.2 节点相关用法
2.21 获得文档根节点Element rootElm = document.getRootElement();2.22 获得某个节点下的指定子节点
Element memberElm = root.element("member");// "member"是节点名 root为某个节点2.23 获得节点下的文字String text = memberElm.getText();
String text = root.elementText("name");2.24 遍历取得某节点下名为member的所有子节点List nodes = rootElm.elements("member");
for (Iterator it = nodes.iterator(); it.hasNext();) {
Element elm = (Element) it.next();
// do something
}2.25 遍历取得某节点下的所有子节点 for (Iterator it = root.elementIterator();it.hasNext();){
Element element = (Element) it.next();
// do something
}2.26 A节点下 Add/Delete B节点Element B = A.addElement("age");
A.remove(B);2.27 在根节点下添加一个CDATA节点
Element contentElm = root.addElement("content");
contentElm.addCDATA("Hello");
// 特别说明：获取节点的CDATA值与获取节点的值是一个方法
System.out.println("contentElm.getText() " + contentElm.getText());2.3 属性相关用法
2.31 取得根节点下的某属性
Element root=document.getRootElement();
Attribute attribute=root.attribute("size");// 属性名name2.32 取得/设置为（Set）上面该属性的文字String text=attribute.getText();2.33 遍历根节点下的所有属性
Element root=document.getRootElement();
for(Iterator it=root.attributeIterator();it.hasNext();){
Attribute attribute = (Attribute) it.next();
String text=attribute.getText();
System.out.println(text);
}2.34 设置某个节点的属性和文字element.addAttribute("name", "sitinspring");2.35 为某节点添加和删除属性// 新建student.xml文件并新增内容
Document document = DocumentHelper.createDocument();
Element root = document.addElement("学生信息");
Element student = root.addElement("学生");
student.addAttribute("sid", "001");Attribute attribute = <span style="font-family: 微软雅黑, sans-serif;">student</span>.attribute("sid");// 属性名name
<span style="font-family: 微软雅黑, sans-serif;">student</span><span style="font-family: 微软雅黑, sans-serif;">.remove(attribute);</span>2.4 文档最后写入MXL文件
OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("GBK"); // 指定XML编码
XMLWriter writer = new XMLWriter(new FileWriter("output.xml"),format);
writer.write(document);
writer.close();2.5 字符串与XML的转换
2.51 字符串 To XML
String text = "<members> <member>sitinspring</member> </members>"; Document document = DocumentHelper.parseText(text);2.52 XML To 字符串
SAXReader reader = new SAXReader();
Document document = reader.read(new File("input.xml"));
Element root = document.getRootElement();
String docXmlText = document.asXML();
String rootXmlText= root.asXML();
Element memberElm = root.element("member");
String memberXmlText = memberElm.asXML();2.6 格式化转义字符问题请查看这篇链接文。
3. 最后一个简单的小例子，看看注释和输出结果，很容易理解。就不多解释了。
程序连续运行两次输出结果如下：
import java.io.File;
import java.io.FileWriter;
import java.util.Iterator;
import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;
public class XML{
public static void main(String[] args) {
try {
XMLWriter writer = null;// 声明写XML的对象
SAXReader reader = new SAXReader();
OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("GBK");// 设置XML文件的编码格式
String filePath = "d:\student.xml";//文件路径
File file = new File(filePath);
if (file.exists()) {
Document document = reader.read(file);// 读取XML文件
Element root = document.getRootElement();// 得到根节点
boolean add_new = false;
for (Iterator i = root.elementIterator(); i.hasNext();) {
Element student = (Element) i.next();
if (student.attributeValue("sid").equals("001")) {
//获取并修改学生sid=001的学生信息
Element info_num = student.element("编号");
System.out.println("sid为001的该属性名为 - " + info_num.getName());
System.out.println("sid为001的该属性值为 - " + info_num.getText());
Element info_name = student.element("姓名");
System.out.println("sid为001的该属性名为 - " + info_name.getName());
System.out.println("sid为001的该属性值为 - " + info_name.getText());
info_name.setName("外号");
info_name.setText("余小二");
System.out.println("sid为001的同学新属性名为 - " + info_name.getName());
System.out.println("sid为001的同学新属性值为 - " + info_name.getText());
writer = new XMLWriter(new FileWriter(filePath), format);
writer.write(document);
writer.close();
add_new = true;
break;
}
}
if (add_new) {
// 添加一个学生信息
Element student = root.addElement("学生");
student.addAttribute("sid", "100");
Element sid = student.addElement("编号");
sid.setText("100");
Element name = student.addElement("姓名");
name.setText("老大");
Element sex = student.addElement("性别");
sex.setText("男");
Element age = student.addElement("年龄");
age.setText("40");
writer = new XMLWriter(new FileWriter(filePath), format);
writer.write(document);
writer.close();
}
} else {
// 新建student.xml文件并新增内容
Document document = DocumentHelper.createDocument();
Element root = document.addElement("学生信息");
Element student = root.addElement("学生");
student.addAttribute("sid", "001");
Element id = student.addElement("编号");
id.setText("001");
Element name = student.addElement("姓名");
name.setText("寂寞");
Element age = student.addElement("年龄");
age.setText("18");
writer = new XMLWriter(new FileWriter(file), format);
writer.write(document);
writer.close();
}
System.out.println("操作结束! ");
} catch (Exception e) {
e.printStackTrace();
}
}