DOM4J介绍与代码示例

DOM4J是dom4j.org出品的一个开源XML解析包。Dom4j是一个易用的、开源的库，用于XML，XPath和XSLT。它应用于Java平台，采用了Java集合框架并完全支持DOM，SAX和JAXP。
DOM4J下载jar包：http://downloads.sourceforge.net/dom4j/dom4j-1.6.1.jar
JAXEN（对XPath的支持）：http://dist.codehaus.org/jaxen/distributions/jaxen-1.1.1.zip
1.DOM4J主要接口
DOM4J主要接口都在org.dom4j这个包里定义。

-Node为所有的dom4j中XML节点定义了多态行为；

-Branch为能够包含子节点的节点如XML元素(Element)和文档(Docuemnts)定义了一个公共的行为；
|-Element 定义XML 元素；
|-Document定义了XML文档；

-DocumentType 定义XML DOCTYPE声明；
-Entity定义 XML entity；
-Attribute定义了XML的属性；
-ProcessingInstruction 定义 XML 处理指令；

-CharacterData是一个标识借口，标识基于字符的节点。如CDATA，Comment, Text；
|- CDATA 定义了XML CDATA 区域；
|-Text 定义XML 文本节点；
|- Comment 定义了XML注释的行为；

项目结构



maven代码

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion>

<groupId>lqy</groupId>
<artifactId>Dom4jTest</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>

<name>Dom4jTest</name>
<url>http://maven.apache.org</url>

<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>

<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>dom4j</groupId>
<artifactId>dom4j</artifactId>
<version>1.6.1</version>
</dependency>
<dependency>
<groupId>jaxen</groupId>
<artifactId>jaxen</artifactId>
<version>1.1.4</version>
</dependency>
</dependencies>
</project>

1.创建XML文档

package lqy.Dom4jTest;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.XMLWriter;

/*
* 创建XML文档
*/
public class XmlGen {

/*
* 方法generateDocumentByMethod()通过调用方法构建xml文档：
1.使用DocumentHelper得到Document实例
Document document = DocumentHelper.createDocument();
2.创建Processing Instruction
document.addProcessingInstruction("xml-stylesheet", inMap);
3.创建元素Element
Element studentsElement = document.addElement("students");
4.为元素添加注释Comment
studentsElement.addComment("An Student Catalog");
5.为元素添加属性
studentsElement.addComment("An Student Catalog");
6.为元素添加文本值Text
ageElement.setText("18");
*/
public Document generateDocumentByMethod() {

Document document = DocumentHelper.createDocument();
// ProcessingInstruction
Map<String, String> inMap = new HashMap<String, String>();
inMap.put("type", "text/xsl");
inMap.put("href", "students.xsl");
document.addProcessingInstruction("xml-stylesheet", inMap);
// root element
Element studentsElement = document.addElement("students");
studentsElement.addComment("An Student Catalog");
// son element
Element stuElement = studentsElement.addElement("student");
stuElement.addAttribute("sn", "01");
Element nameElement = stuElement.addElement("name");
nameElement.setText("sam");
Element ageElement = stuElement.addElement("age");
ageElement.setText("18");
// son element
Element anotherStuElement = studentsElement.addElement("student");
anotherStuElement.addAttribute("sn", "02");
Element anotherNameElement = anotherStuElement.addElement("name");
anotherNameElement.setText("lin");
Element anotherAgeElement = anotherStuElement.addElement("age");
anotherAgeElement.setText("20");

return document;
}

/*
* 方法generateDocumentByString()通过字符串转换直接构建xml文档，使用DocumentHelper.parseText()来实现.
* document = DocumentHelper.parseText(text);
*/
public Document generateDocumentByString() {
String text = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +
"<?xml-stylesheet type=\"text/xsl\" href=\"students.xsl\"?>" +
"<students><!--An Student Catalog-->   <student sn=\"01\">" +
"<name>sam</name><age>18</age></student><student sn=\"02\">" +
"<name>lin</name><age>20</age></student></students>";
Document document = null;
try {
document = DocumentHelper.parseText(text);
} catch (DocumentException e) {
e.printStackTrace();
}
return document;
}

public void saveDocument(Document document, File outputXml) {
try {
// 美化格式
OutputFormat format = OutputFormat.createPrettyPrint();
/*// 缩减格式
OutputFormat format = OutputFormat.createCompactFormat();*/
/*// 指定XML编码
format.setEncoding("GBK");*/
XMLWriter output = new XMLWriter(new FileWriter(outputXml), format);
output.write(document);
output.close();
} catch (IOException e) {
System.out.println(e.getMessage());
}
}

public static void main(String[] argv) {
XmlGen dom4j = new XmlGen();
Document document = null;
//通过方法生成
document=dom4j.generateDocumentByMethod();

//通过字符串生成
//document = dom4j.generateDocumentByString();
dom4j.saveDocument(document, new File("students-gen.xml"));
}
}

生成students-gen.xml如下

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="students.xsl"?>

<students>
<!--An Student Catalog-->
<student sn="01">
<name>sam</name>
<age>18</age>
</student>
<student sn="02">
<name>lin</name>
<age>20</age>
</student>
</students>

方法generateDocumentByMethod()通过调用方法构建xml文档：
1.使用DocumentHelper得到Document实例
Document document = DocumentHelper.createDocument();
2.创建Processing Instruction
document.addProcessingInstruction("xml-stylesheet", inMap);
3.创建元素Element
Element studentsElement = document.addElement("students");
4.为元素添加注释Comment
studentsElement.addComment("An Student Catalog");
5.为元素添加属性
studentsElement.addComment("An Student Catalog");
6.为元素添加文本值Text
ageElement.setText("18");

方法generateDocumentByString()通过字符串转换直接构建xml文档，使用DocumentHelper.parseText()来实现.
[align=left]document = DocumentHelper.parseText(text);[/align]

方法saveDocument(Document document, File outputXml)将文档输出到文件保存，可指定字符编码，可指定格式化输出。

2.修改XML文档

package lqy.Dom4jTest;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;

/*
* 这里使用xpath来定位待修改的元素和属性，需要jaxen的支持。
*示例中将students-gen.xml的第一个student元素的sn属性改为001，其子元素name内容改为jeff。
*XmlMod.java
*/
public class XmlMod {

/*
* 1.使用File定位文件资源，并基于此获得Document实例
*SAXReader saxReader = new SAXReader();
*Document document = saxReader.read(inputXml);
*2.Document实例的selectNodes方法可以传入xpath，并返回一个List实例，基于此使用迭代器，完成特定的应用
*List list = document.selectNodes("//students/student/@sn");
*/
public void modifyDocument(File inputXml) {
try {
SAXReader saxReader = new SAXReader();
Document document = saxReader.read(inputXml);

List list = document.selectNodes("//students/student/@sn");
Iterator iter = list.iterator();
while (iter.hasNext()) {
Attribute attribute = (Attribute) iter.next();
if (attribute.getValue().equals("01"))
attribute.setValue("001");
}
list = document.selectNodes("//students/student");
iter = list.iterator();
while (iter.hasNext()) {
Element element = (Element) iter.next();
Iterator iterator = element.elementIterator("name");
while (iterator.hasNext()) {
Element nameElement = (Element) iterator.next();
if (nameElement.getText().equals("sam"))
nameElement.setText("jeff");
}
}
XMLWriter output = new XMLWriter(new FileWriter(new File(
"students-modified.xml")));
output.write(document);
output.close();
}

catch (DocumentException e) {
System.out.println(e.getMessage());
} catch (IOException e) {
System.out.println(e.getMessage());
}
}

/*
* selectSingleNode如果有多个只取第一个
*/
public void modifyDocument2(File inputXml){
SAXReader saxReader = new SAXReader();
try {
Document document = saxReader.read(inputXml);
Node nodeAttr=document.selectSingleNode("//students/student/@sn");
System.out.println(nodeAttr.getText());
nodeAttr.setText("nodeAttr");

Node nodeEle=document.selectSingleNode("//students/student");
System.out.println(nodeEle.getText());
nodeEle.setText("nodeEle");

XMLWriter output = new XMLWriter(new FileWriter(new File(
"students-modified2.xml")));
output.write(document);
output.close();
} catch (Exception e) {
e.printStackTrace();
}

}

public static void main(String[] argv) {
XmlMod dom4jParser = new XmlMod();
//dom4jParser.modifyDocument(new File("students-gen.xml"));
dom4jParser. modifyDocument2(new File("students-gen.xml"));
}
}

生成students-modified.xml

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="students.xsl"?><students>
<!--An Student Catalog-->
<student sn="001">
<name>jeff</name>
<age>18</age>
</student>
<student sn="02">
<name>lin</name>
<age>20</age>
</student>
</students>

生成students-modified2.xml

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="students.xsl"?><students>
<!--An Student Catalog-->
<student sn="nodeAttr"><name>sam</name><age>18</age>nodeEle</student>
<student sn="02">
<name>lin</name>
<age>20</age>
</student>
</students>

1.使用File定位文件资源，并基于此获得Document实例
[align=left]SAXReader saxReader = new SAXReader();[/align]
Document document = saxReader.read(inputXml);
2.Document实例的selectNodes方法可以传入xpath，并返回一个List实例，基于此使用迭代器，完成特定的应用
List list = document.selectNodes("//students/student/@sn");

3.遍历XML文档

这里提供两种遍历方法，一种是基于迭代的遍历，一种是基于Visitor模式的遍历。这里介绍迭代的

package lqy.Dom4jTest;

import java.io.File;
import java.util.Iterator;

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

/*
* 方法traversalDocumentByIterator()提供一种基于迭代的遍历实现，每个Element通过elementIterator()和attributeIterator()取代其子元素和属性的迭代器。
*/
public class XmlIterator {

private File inputXml;

public XmlIterator(File inputXml) {
this.inputXml = inputXml;
}

public static void main(String[] argv) {
XmlIterator dom4jParser = new XmlIterator(new File("students-gen.xml"));
dom4jParser.traversalDocumentByIterator();
}

public Element getRootElement() {
return getDocument().getRootElement();
}

public Document getDocument() {
SAXReader saxReader = new SAXReader();
Document document = null;
try {
document = saxReader.read(inputXml);
} catch (Exception e) {
e.printStackTrace();
}
return document;
}

/*
* 该方法只是枚举了两层，如果一直挖的话要用递归方法
*/
public void traversalDocumentByIterator() {
Element root = getRootElement();
// 枚举根节点下所有子节点
for (Iterator ie = root.elementIterator(); ie.hasNext();) {
System.out.println("======");
Element element = (Element) ie.next();
System.out.println(element.getName());

// 枚举属性
for (Iterator ia = element.attributeIterator(); ia.hasNext();) {
Attribute attribute = (Attribute) ia.next();
System.out.println(attribute.getName() + ":"
+ attribute.getData());
}

// 枚举当前节点下所有子节点
for (Iterator ieson = element.elementIterator(); ieson.hasNext();) {
Element elementSon = (Element) ieson.next();
System.out.println(elementSon.getName() + ":"+ elementSon.getText());
}
}
}

}

输出



4.通过Element找到节点

package lqy.Dom4jTest;

import java.io.File;
import java.util.Iterator;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;

public class XmlReadByElement {

/**
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {

XmlReadByElement.getOneEle();
XmlReadByElement.getEles();
XmlReadByElement.getAttrs();
XmlReadByElement.getOneAttr();
}

public static Document getDocument() throws Exception{
SAXReader reader = new SAXReader();
Document  document = reader.read(new File("students-read.xml"));
return document;
}

//要顺序一个一个往下找
public static void getOneEle() throws Exception{
Document  document=getDocument();
Element rootElm = document.getRootElement();
Element e=rootElm.element("lqy");
System.out.println("arrt:"+e.attributeValue("aa"));
Element e2=e.element("login");
System.out.println("text:"+e2.getText());

}

public static void getEles() throws Exception{
Document  document=getDocument();
Element rootElm = document.getRootElement();
List eList=rootElm.elements("student");
Iterator it=eList.iterator();
while(it.hasNext()){
Element elm=(Element)it.next();
System.out.println("arrt:"+elm.attributeValue("sn"));
}

}

public static void getOneAttr() throws Exception{
Document  document=getDocument();
Node node1=document.selectSingleNode("//students/lqy/login");
Element elm=(Element)node1;
System.out.println("attr:"+elm.attributeValue("sn"));

}

public static void getAttrs() throws Exception{
Document  document=getDocument();
List list = document.selectNodes("//students/student");
Iterator it=list.iterator();
while(it.hasNext()){
Element elm=(Element)it.next();
System.out.println("attr:"+elm.attributeValue("sn"));
}

}

}

students-read.xml

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="students.xsl"?>

<students>
<!--An Student Catalog-->
<student sn="01">
<name>sam</name>
<age>18</age>
</student>
<student sn="02">
<name>lin</name>
<age>20</age>
</student>
<lqy aa="123123123">
<login sn="03">luo</login>
<pass>123456</pass>
</lqy>
</students>

输出结果



5[b].通过XPath找到节点[/b]

package lqy.Dom4jTest;

import java.io.File;
import java.util.Iterator;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;

public class XmlReadByXPath {

/**
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {

XmlReadByXPath.getOneEleByXPath();
XmlReadByXPath.getElesByXPath();
XmlReadByXPath.getAttrsByXPath();
XmlReadByXPath.getOneAttrByXPath();
}

public static Document getDocument() throws Exception{
SAXReader reader = new SAXReader();
Document  document = reader.read(new File("students-read.xml"));
return document;
}

public static void getOneEleByXPath() throws Exception{
Document  document=getDocument();
Node node1=document.selectSingleNode("//students/lqy/login");
String nodeText1=node1.getText();
System.out.println("nodeText1："+nodeText1);

//假如多个只返回第一个
Node node2=document.selectSingleNode("//students/student/name");
String nodeText2=node2.getText();
System.out.println("nodeText2："+nodeText2);

Node node3=document.selectSingleNode("//students/student/@sn");
short nodeText3=node1.ATTRIBUTE_NODE;
System.out.println("nodeText3："+nodeText3);

}

public static void getElesByXPath() throws Exception{
Document  document=getDocument();
List list = document.selectNodes("//students/student/name");
Iterator it=list.iterator();
while(it.hasNext()){
Element elm=(Element)it.next();
System.out.println("elm:"+elm.getText());
}

}

public static void getOneAttrByXPath() throws Exception{
Document  document=getDocument();
Node node1=document.selectSingleNode("//students/lqy/login");
Element elm=(Element)node1;
System.out.println("attr:"+elm.attributeValue("sn"));

}

public static void getAttrsByXPath() throws Exception{
Document  document=getDocument();
List list = document.selectNodes("//students/student");
Iterator it=list.iterator();
while(it.hasNext()){
Element elm=(Element)it.next();
System.out.println("attr:"+elm.attributeValue("sn"));
}

}

}

输出结果



6[b].XML转换成String[/b]

package lqy.Dom4jTest;

import java.io.File;
import java.util.Iterator;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;

public class XMLToString {

/**
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
SAXReader reader = new SAXReader();
Document  document = reader.read(new File("students-read.xml"));
String docXmlText=document.asXML();
System.out.println(docXmlText);
System.out.println("------------------docXmlText-------------------");
Element root=document.getRootElement();
String rootXmlText=root.asXML();
System.out.println(rootXmlText);
System.out.println("------------------rootXmlText-------------------");
Element memberElm=root.element("lqy");
String memberXmlText=memberElm.asXML();
System.out.println(memberXmlText);
System.out.println("------------------memberXmlText-------------------");

}

}

输出



参考

1.http://zhangjunhd.blog.51cto.com/113473/126310

2.http://www.blogjava.net/junglesong/archive/2008/02/21/181196.html