Java解析XML汇总（DOM/SAX/JDOM/DOM4j/XPath）

【目录】

一、【基础知识——扫盲】

二、【DOM、SAX、JDOM、DOM4j简单使用介绍】

三、【性能测试】

四、【对比】

五、【小插曲XPath】

六、【补充】

关键字：Java解析xml、解析xml四种方法、DOM、SAX、JDOM、DOM4j、XPath

【引言】

目前在Java中用于解析XML的技术很多，主流的有DOM、SAX、JDOM、DOM4j，下文主要介绍这4种解析XML文档技术的使用、优缺点及性能测试。

一、【基础知识——扫盲】

sax、dom是两种对xml文档进行解析的方法(没有具体实现，只是接口)，所以只有它们是无法解析xml文档的；jaxp只是api，它进一步封装了sax、dom两种接口，并且提供了DomcumentBuilderFactory/DomcumentBuilder和SAXParserFactory/SAXParser（默认使用xerces解释器）。

二、【DOM、SAX、JDOM、DOM4j简单使用介绍】

1、【DOM(Document Object Model) 】

由W3C提供的接口，它将整个XML文档读入内存，构建一个DOM树来对各个节点(Node)进行操作。

示例代码：

[html]
view plaincopyprint?

<?xml version="1.0" encoding="UTF-8"?>
<university name="pku">
<college name="c1">
<class name="class1">
<student name="stu1" sex='male' age="21" />
<student name="stu2" sex='female' age="20" />
<student name="stu3" sex='female' age="20" />
</class>
<class name="class2">
<student name="stu4" sex='male' age="19" />
<student name="stu5" sex='female' age="20" />
<student name="stu6" sex='female' age="21" />
</class>
</college>
<college name="c2">
<class name="class3">
<student name="stu7" sex='male' age="20" />
</class>
</college>
<college name="c3">
</college>
</university>

[java]
view plaincopyprint?

package test.xml;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.parsers.ParserConfigurationException;

import javax.xml.transform.Transformer;

import javax.xml.transform.TransformerConfigurationException;

import javax.xml.transform.TransformerException;

import javax.xml.transform.TransformerFactory;

import javax.xml.transform.dom.DOMSource;

import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;

import org.w3c.dom.Element;

import org.w3c.dom.Node;

import org.w3c.dom.NodeList;

import org.w3c.dom.Text;

import org.xml.sax.SAXException;

/**
* dom读写xml
* @author whwang
*/
public class TestDom {

public static void main(String[] args) {

read();
//write();
}

public static void read() {

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

try {

DocumentBuilder builder = dbf.newDocumentBuilder();

InputStream in = TestDom.class.getClassLoader().getResourceAsStream("test.xml");

Document doc = builder.parse(in);
// root <university>

Element root = doc.getDocumentElement();
if (root == null) return;

System.err.println(root.getAttribute("name"));

// all college node

NodeList collegeNodes = root.getChildNodes();
if (collegeNodes == null) return;

for(int i = 0; i < collegeNodes.getLength(); i++) {

Node college = collegeNodes.item(i);

if (college != null && college.getNodeType() == Node.ELEMENT_NODE) {

System.err.println("\t" + college.getAttributes().getNamedItem("name").getNodeValue());

// all class node

NodeList classNodes = college.getChildNodes();

if (classNodes == null) continue;

for (int j = 0; j < classNodes.getLength(); j++) {

Node clazz = classNodes.item(j);
if (clazz != null && clazz.getNodeType() == Node.ELEMENT_NODE) {

System.err.println("\t\t" + clazz.getAttributes().getNamedItem("name").getNodeValue());

// all student node

NodeList studentNodes = clazz.getChildNodes();

if (studentNodes == null) continue;

for (int k = 0; k < studentNodes.getLength(); k++) {

Node student = studentNodes.item(k);

if (student != null && student.getNodeType() == Node.ELEMENT_NODE) {

System.err.print("\t\t\t" + student.getAttributes().getNamedItem("name").getNodeValue());

System.err.print(" " + student.getAttributes().getNamedItem("sex").getNodeValue());

System.err.println(" " + student.getAttributes().getNamedItem("age").getNodeValue());

}
}
}
}
}
}
} catch (ParserConfigurationException e) {

e.printStackTrace();
} catch (FileNotFoundException e) {

e.printStackTrace();
} catch (SAXException e) {

e.printStackTrace();
} catch (IOException e) {

e.printStackTrace();
}

}

public static void write() {

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

try {
DocumentBuilder builder = dbf.newDocumentBuilder();

InputStream in = TestDom.class.getClassLoader().getResourceAsStream("test.xml");

Document doc = builder.parse(in);
// root <university>

Element root = doc.getDocumentElement();

if (root == null) return;

// 修改属性

root.setAttribute("name", "tsu");

NodeList collegeNodes = root.getChildNodes();

if (collegeNodes != null) {

for (int i = 0; i <collegeNodes.getLength() - 1; i++) {

// 删除节点

Node college = collegeNodes.item(i);

if (college.getNodeType() == Node.ELEMENT_NODE) {

String collegeName = college.getAttributes().getNamedItem("name").getNodeValue();

if ("c1".equals(collegeName) || "c2".equals(collegeName)) {

root.removeChild(college);

} else if ("c3".equals(collegeName)) {

Element newChild = doc.createElement("class");

newChild.setAttribute("name", "c4");

college.appendChild(newChild);

}
}
}
}
// 新增节点

Element addCollege = doc.createElement("college");

addCollege.setAttribute("name", "c5");

root.appendChild(addCollege);
Text text = doc.createTextNode("text");

addCollege.appendChild(text);

// 将修改后的文档保存到文件

TransformerFactory transFactory = TransformerFactory.newInstance();

Transformer transFormer = transFactory.newTransformer();

DOMSource domSource = new DOMSource(doc);

File file = new File("src/dom-modify.xml");

if (file.exists()) {

file.delete();
}
file.createNewFile();
FileOutputStream out = new FileOutputStream(file);

StreamResult xmlResult = new StreamResult(out);

transFormer.transform(domSource, xmlResult);
System.out.println(file.getAbsolutePath());

} catch (ParserConfigurationException e) {

e.printStackTrace();
} catch (SAXException e) {

e.printStackTrace();
} catch (IOException e) {

e.printStackTrace();
} catch (TransformerConfigurationException e) {

e.printStackTrace();
} catch (TransformerException e) {

e.printStackTrace();
}
}
}

package test.xml;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;
import org.xml.sax.SAXException;

/**
* dom读写xml
* @author whwang
*/
public class TestDom {

public static void main(String[] args) {
read();
//write();
}

public static void read() {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = dbf.newDocumentBuilder();
InputStream in = TestDom.class.getClassLoader().getResourceAsStream("test.xml");
Document doc = builder.parse(in);
// root <university>
Element root = doc.getDocumentElement();
if (root == null) return;
System.err.println(root.getAttribute("name"));
// all college node
NodeList collegeNodes = root.getChildNodes();
if (collegeNodes == null) return;
for(int i = 0; i < collegeNodes.getLength(); i++) {
Node college = collegeNodes.item(i);
if (college != null && college.getNodeType() == Node.ELEMENT_NODE) {
System.err.println("\t" + college.getAttributes().getNamedItem("name").getNodeValue());
// all class node
NodeList classNodes = college.getChildNodes();
if (classNodes == null) continue;
for (int j = 0; j < classNodes.getLength(); j++) {
Node clazz = classNodes.item(j);
if (clazz != null && clazz.getNodeType() == Node.ELEMENT_NODE) {
System.err.println("\t\t" + clazz.getAttributes().getNamedItem("name").getNodeValue());
// all student node
NodeList studentNodes = clazz.getChildNodes();
if (studentNodes == null) continue;
for (int k = 0; k < studentNodes.getLength(); k++) {
Node student = studentNodes.item(k);
if (student != null && student.getNodeType() == Node.ELEMENT_NODE) {
System.err.print("\t\t\t" + student.getAttributes().getNamedItem("name").getNodeValue());
System.err.print(" " + student.getAttributes().getNamedItem("sex").getNodeValue());
System.err.println(" " + student.getAttributes().getNamedItem("age").getNodeValue());
}
}
}
}
}
}
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

}

public static void write() {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = dbf.newDocumentBuilder();
InputStream in = TestDom.class.getClassLoader().getResourceAsStream("test.xml");
Document doc = builder.parse(in);
// root <university>
Element root = doc.getDocumentElement();
if (root == null) return;
// 修改属性
root.setAttribute("name", "tsu");
NodeList collegeNodes = root.getChildNodes();
if (collegeNodes != null) {
for (int i = 0; i <collegeNodes.getLength() - 1; i++) {
// 删除节点
Node college = collegeNodes.item(i);
if (college.getNodeType() == Node.ELEMENT_NODE) {
String collegeName = college.getAttributes().getNamedItem("name").getNodeValue();
if ("c1".equals(collegeName) || "c2".equals(collegeName)) {
root.removeChild(college);
} else if ("c3".equals(collegeName)) {
Element newChild = doc.createElement("class");
newChild.setAttribute("name", "c4");
college.appendChild(newChild);
}
}
}
}
// 新增节点
Element addCollege = doc.createElement("college");
addCollege.setAttribute("name", "c5");
root.appendChild(addCollege);
Text text = doc.createTextNode("text");
addCollege.appendChild(text);

// 将修改后的文档保存到文件
TransformerFactory transFactory = TransformerFactory.newInstance();
Transformer transFormer = transFactory.newTransformer();
DOMSource domSource = new DOMSource(doc);
File file = new File("src/dom-modify.xml");
if (file.exists()) {
file.delete();
}
file.createNewFile();
FileOutputStream out = new FileOutputStream(file);
StreamResult xmlResult = new StreamResult(out);
transFormer.transform(domSource, xmlResult);
System.out.println(file.getAbsolutePath());
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (TransformerConfigurationException e) {
e.printStackTrace();
} catch (TransformerException e) {
e.printStackTrace();
}
}
}

该代码只要稍做修改，即可变得更加简洁，无需一直写if来判断是否有子节点。

2、【SAX (Simple API for XML) 】

SAX不用将整个文档加载到内存，基于事件驱动的API(Observer模式)，用户只需要注册自己感兴趣的事件即可。SAX提供EntityResolver, DTDHandler, ContentHandler, ErrorHandler接口，分别用于监听解析实体事件、DTD处理事件、正文处理事件和处理出错事件，与AWT类似，SAX还提供了一个对这4个接口默认的类DefaultHandler（这里的默认实现，其实就是一个空方法），一般只要继承DefaultHandler，重写自己感兴趣的事件即可。

示例代码：

[java]
view plaincopyprint?

package test.xml;

import java.io.IOException;

import java.io.InputStream;

import javax.xml.parsers.ParserConfigurationException;

import javax.xml.parsers.SAXParser;

import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;

import org.xml.sax.InputSource;

import org.xml.sax.Locator;

import org.xml.sax.SAXException;

import org.xml.sax.SAXParseException;

import org.xml.sax.helpers.DefaultHandler;

/**
*
* @author whwang
*/
public class TestSAX {

public static void main(String[] args) {

read();
write();
}

public static void read() {

try {

SAXParserFactory factory = SAXParserFactory.newInstance();

SAXParser parser = factory.newSAXParser();

InputStream in = TestSAX.class.getClassLoader().getResourceAsStream("test.xml");

parser.parse(in, new MyHandler());

} catch (ParserConfigurationException e) {

e.printStackTrace();
} catch (SAXException e) {

e.printStackTrace();
} catch (IOException e) {

e.printStackTrace();
}
}

public static void write() {

System.err.println("纯SAX对于写操作无能为力");

}

}

// 重写对自己感兴趣的事件处理方法

class MyHandler extends DefaultHandler {

@Override
public InputSource resolveEntity(String publicId, String systemId)

throws IOException, SAXException {

return super.resolveEntity(publicId, systemId);

}

@Override
public void notationDecl(String name, String publicId, String systemId)

throws SAXException {

super.notationDecl(name, publicId, systemId);

}

@Override
public void unparsedEntityDecl(String name, String publicId,

String systemId, String notationName) throws SAXException {

super.unparsedEntityDecl(name, publicId, systemId, notationName);

}

@Override
public void setDocumentLocator(Locator locator) {

super.setDocumentLocator(locator);

}

@Override

public void startDocument() throws SAXException {

System.err.println("开始解析文档");

}

@Override
public void endDocument() throws SAXException {

System.err.println("解析结束");

}

@Override

public void startPrefixMapping(String prefix, String uri)

throws SAXException {

super.startPrefixMapping(prefix, uri);

}

@Override

public void endPrefixMapping(String prefix) throws SAXException {

super.endPrefixMapping(prefix);

}

@Override
public void startElement(String uri, String localName, String qName,

Attributes attributes) throws SAXException {

System.err.print("Element: " + qName + ", attr: ");

print(attributes);
}

@Override

public void endElement(String uri, String localName, String qName)

throws SAXException {

super.endElement(uri, localName, qName);

}

@Override

public void characters(char[] ch, int start, int length)

throws SAXException {

super.characters(ch, start, length);

}

@Override

public void ignorableWhitespace(char[] ch, int start, int length)

throws SAXException {

super.ignorableWhitespace(ch, start, length);

}

@Override

public void processingInstruction(String target, String data)

throws SAXException {

super.processingInstruction(target, data);

}

@Override

public void skippedEntity(String name) throws SAXException {

super.skippedEntity(name);

}

@Override
public void warning(SAXParseException e) throws SAXException {

super.warning(e);

}

@Override

public void error(SAXParseException e) throws SAXException {

super.error(e);

}

@Override
public void fatalError(SAXParseException e) throws SAXException {

super.fatalError(e);

}

private void print(Attributes attrs) {

if (attrs == null) return;

System.err.print("[");

for (int i = 0; i < attrs.getLength(); i++) {

System.err.print(attrs.getQName(i) + " = " + attrs.getValue(i));

if (i != attrs.getLength() - 1) {

System.err.print(", ");

}
}
System.err.println("]");

}
}

[java]
view plaincopyprint?

package test.xml;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.util.List;

import org.jdom.Attribute;

import org.jdom.Document;

import org.jdom.Element;

import org.jdom.JDOMException;

import org.jdom.input.SAXBuilder;

import org.jdom.output.XMLOutputter;

/**
* JDom读写xml
* @author whwang
*/
public class TestJDom {

public static void main(String[] args) {

//read();
write();
}

public static void read() {

try {

boolean validate = false;

SAXBuilder builder = new SAXBuilder(validate);

InputStream in = TestJDom.class.getClassLoader().getResourceAsStream("test.xml");

Document doc = builder.build(in);
// 获取根节点 <university>

Element root = doc.getRootElement();
readNode(root, "");

} catch (JDOMException e) {

e.printStackTrace();
} catch (IOException e) {

e.printStackTrace();
}
}

@SuppressWarnings("unchecked")

public static void readNode(Element root, String prefix) {

if (root == null) return;

// 获取属性

List<Attribute> attrs = root.getAttributes();
if (attrs != null && attrs.size() > 0) {

System.err.print(prefix);
for (Attribute attr : attrs) {

System.err.print(attr.getValue() + " ");

}
System.err.println();
}
// 获取他的子节点
List<Element> childNodes = root.getChildren();

prefix += "\t";

for (Element e : childNodes) {

readNode(e, prefix);
}
}

public static void write() {

boolean validate = false;

try {
SAXBuilder builder = new SAXBuilder(validate);

InputStream in = TestJDom.class.getClassLoader().getResourceAsStream("test.xml");

Document doc = builder.build(in);
// 获取根节点 <university>

Element root = doc.getRootElement();
// 修改属性

root.setAttribute("name", "tsu");

// 删除
boolean isRemoved = root.removeChildren("college");

System.err.println(isRemoved);
// 新增

Element newCollege = new Element("college");

newCollege.setAttribute("name", "new_college");

Element newClass = new Element("class");

newClass.setAttribute("name", "ccccc");

newCollege.addContent(newClass);
root.addContent(newCollege);
XMLOutputter out = new XMLOutputter();

File file = new File("src/jdom-modify.xml");

if (file.exists()) {

file.delete();
}
file.createNewFile();
FileOutputStream fos = new FileOutputStream(file);

out.output(doc, fos);
} catch (JDOMException e) {

e.printStackTrace();
} catch (IOException e) {

e.printStackTrace();
}
}

}

package test.xml;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import org.jdom.Attribute;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;
import org.jdom.output.XMLOutputter;

/**
* JDom读写xml
* @author whwang
*/
public class TestJDom {
public static void main(String[] args) {
//read();
write();
}

public static void read() {
try {
boolean validate = false;
SAXBuilder builder = new SAXBuilder(validate);
InputStream in = TestJDom.class.getClassLoader().getResourceAsStream("test.xml");
Document doc = builder.build(in);
// 获取根节点 <university>
Element root = doc.getRootElement();
readNode(root, "");
} catch (JDOMException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

@SuppressWarnings("unchecked")
public static void readNode(Element root, String prefix) {
if (root == null) return;
// 获取属性
List<Attribute> attrs = root.getAttributes();
if (attrs != null && attrs.size() > 0) {
System.err.print(prefix);
for (Attribute attr : attrs) {
System.err.print(attr.getValue() + " ");
}
System.err.println();
}
// 获取他的子节点
List<Element> childNodes = root.getChildren();
prefix += "\t";
for (Element e : childNodes) {
readNode(e, prefix);
}
}

public static void write() {
boolean validate = false;
try {
SAXBuilder builder = new SAXBuilder(validate);
InputStream in = TestJDom.class.getClassLoader().getResourceAsStream("test.xml");
Document doc = builder.build(in);
// 获取根节点 <university>
Element root = doc.getRootElement();
// 修改属性
root.setAttribute("name", "tsu");
// 删除
boolean isRemoved = root.removeChildren("college");
System.err.println(isRemoved);
// 新增
Element newCollege = new Element("college");
newCollege.setAttribute("name", "new_college");
Element newClass = new Element("class");
newClass.setAttribute("name", "ccccc");
newCollege.addContent(newClass);
root.addContent(newCollege);
XMLOutputter out = new XMLOutputter();
File file = new File("src/jdom-modify.xml");
if (file.exists()) {
file.delete();
}
file.createNewFile();
FileOutputStream fos = new FileOutputStream(file);
out.output(doc, fos);
} catch (JDOMException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

}

4、【DOM4j】

dom4j是目前在xml解析方面是最优秀的(Hibernate、Sun的JAXM也都使用dom4j来解析XML)，它合并了许多超出基本 XML 文档表示的功能，包括集成的 XPath 支持、XML Schema 支持以及用于大文档或流化文档的基于事件的处理

示例代码：

[java]
view plaincopyprint?

package test.xml;

import java.io.File;

import java.io.FileWriter;

import java.io.IOException;

import java.io.InputStream;

import java.util.List;

import org.dom4j.Attribute;

import org.dom4j.Document;

import org.dom4j.DocumentException;

import org.dom4j.DocumentHelper;

import org.dom4j.Element;

import org.dom4j.ProcessingInstruction;

import org.dom4j.VisitorSupport;

import org.dom4j.io.SAXReader;

import org.dom4j.io.XMLWriter;

/**
* Dom4j读写xml
* @author whwang
*/
public class TestDom4j {

public static void main(String[] args) {

read1();
//read2();
//write();

}

public static void read1() {

try {

SAXReader reader = new SAXReader();

InputStream in = TestDom4j.class.getClassLoader().getResourceAsStream("test.xml");

Document doc = reader.read(in);
Element root = doc.getRootElement();
readNode(root, "");

} catch (DocumentException e) {

e.printStackTrace();
}
}

@SuppressWarnings("unchecked")

public static void readNode(Element root, String prefix) {

if (root == null) return;

// 获取属性

List<Attribute> attrs = root.attributes();
if (attrs != null && attrs.size() > 0) {

System.err.print(prefix);
for (Attribute attr : attrs) {

System.err.print(attr.getValue() + " ");

}
System.err.println();
}
// 获取他的子节点
List<Element> childNodes = root.elements();

prefix += "\t";

for (Element e : childNodes) {

readNode(e, prefix);
}
}

public static void read2() {

try {

SAXReader reader = new SAXReader();

InputStream in = TestDom4j.class.getClassLoader().getResourceAsStream("test.xml");

Document doc = reader.read(in);
doc.accept(new MyVistor());

} catch (DocumentException e) {

e.printStackTrace();
}
}

public static void write() {

try {
// 创建一个xml文档

Document doc = DocumentHelper.createDocument();
Element university = doc.addElement("university");

university.addAttribute("name", "tsu");

// 注释

university.addComment("这个是根节点");

Element college = university.addElement("college");

college.addAttribute("name", "cccccc");

college.setText("text");

File file = new File("src/dom4j-modify.xml");

if (file.exists()) {

file.delete();
}
file.createNewFile();
XMLWriter out = new XMLWriter(new FileWriter(file));

out.write(doc);
out.flush();
out.close();
} catch (IOException e) {

e.printStackTrace();
}
}
}

class MyVistor extends VisitorSupport {

public void visit(Attribute node) {

System.out.println("Attibute: " + node.getName() + "="

+ node.getValue());
}

public void visit(Element node) {

if (node.isTextOnly()) {

System.out.println("Element: " + node.getName() + "="

+ node.getText());
} else {
System.out.println(node.getName());
}
}

@Override

public void visit(ProcessingInstruction node) {

System.out.println("PI:" + node.getTarget() + " " + node.getText());

}
}

[java]
view plaincopyprint?

package test.xml;

import java.io.IOException;

import java.io.InputStream;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.parsers.ParserConfigurationException;

import javax.xml.xpath.XPath;

import javax.xml.xpath.XPathConstants;

import javax.xml.xpath.XPathExpression;

import javax.xml.xpath.XPathExpressionException;

import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;

import org.w3c.dom.NodeList;

import org.xml.sax.SAXException;

public class TestXPath {

public static void main(String[] args) {

read();
}

public static void read() {

try {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

DocumentBuilder builder = dbf.newDocumentBuilder();

InputStream in = TestXPath.class.getClassLoader().getResourceAsStream("test.xml");

Document doc = builder.parse(in);
XPathFactory factory = XPathFactory.newInstance();

XPath xpath = factory.newXPath();
// 选取所有class元素的name属性

// XPath语法介绍： http://w3school.com.cn/xpath/ 
XPathExpression expr = xpath.compile("//class/@name");

NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);

for (int i = 0; i < nodes.getLength(); i++) {

System.out.println("name = " + nodes.item(i).getNodeValue());

}
} catch (XPathExpressionException e) {

e.printStackTrace();
} catch (ParserConfigurationException e) {

e.printStackTrace();
} catch (SAXException e) {

e.printStackTrace();
} catch (IOException e) {

e.printStackTrace();
}
}

}

package test.xml;

import java.io.IOException;
import java.io.InputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class TestXPath {

public static void main(String[] args) {
read();
}

public static void read() {
try {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = dbf.newDocumentBuilder();
InputStream in = TestXPath.class.getClassLoader().getResourceAsStream("test.xml");
Document doc = builder.parse(in);
XPathFactory factory = XPathFactory.newInstance();
XPath xpath = factory.newXPath();
// 选取所有class元素的name属性
// XPath语法介绍： http://w3school.com.cn/xpath/ XPathExpression expr = xpath.compile("//class/@name");
NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
for (int i = 0; i < nodes.getLength(); i++) {
System.out.println("name = " + nodes.item(i).getNodeValue());
}
} catch (XPathExpressionException e) {
e.printStackTrace();
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

}

六、【补充】

注意4种解析方法对TextNode（文本节点）的处理：

1、在使用DOM时，调用node.getChildNodes()获取该节点的子节点，文本节点也会被当作一个Node来返回，如：

[html]
view plaincopyprint?

<?xml version="1.0" encoding="UTF-8"?>

<university name="pku">

<college name="c1">

<class name="class1">

<student name="stu1" sex='male' age="21" />

<student name="stu2" sex='female' age="20" />

<student name="stu3" sex='female' age="20" />

</class>

</college>

</university>

[java]
view plaincopyprint?

package test.xml;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.InputStream;

import java.util.Arrays;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;

import org.w3c.dom.Element;

import org.w3c.dom.Node;

import org.w3c.dom.NodeList;

import org.xml.sax.SAXException;

/**
* dom读写xml
* @author whwang
*/
public class TestDom2 {

public static void main(String[] args) {

read();
}

public static void read() {

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

try {
DocumentBuilder builder = dbf.newDocumentBuilder();

InputStream in = TestDom2.class.getClassLoader().getResourceAsStream("test.xml");

Document doc = builder.parse(in);
// root <university>

Element root = doc.getDocumentElement();

if (root == null) return;

//          System.err.println(root.getAttribute("name"));

// all college node

NodeList collegeNodes = root.getChildNodes();

if (collegeNodes == null) return;

System.err.println("university子节点数：" + collegeNodes.getLength());

System.err.println("子节点如下：");

for(int i = 0; i < collegeNodes.getLength(); i++) {

Node college = collegeNodes.item(i);
if (college == null) continue;

if (college.getNodeType() == Node.ELEMENT_NODE) {

System.err.println("\t元素节点：" + college.getNodeName());

} else if (college.getNodeType() == Node.TEXT_NODE) {

System.err.println("\t文本节点：" + Arrays.toString(college.getTextContent().getBytes()));

}
}
} catch (ParserConfigurationException e) {

e.printStackTrace();
} catch (FileNotFoundException e) {

e.printStackTrace();
} catch (SAXException e) {

e.printStackTrace();
} catch (IOException e) {

e.printStackTrace();
}

}
}

package test.xml;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

/**
* dom读写xml
* @author whwang
*/
public class TestDom2 {

public static void main(String[] args) {
read();
}

public static void read() {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = dbf.newDocumentBuilder();
InputStream in = TestDom2.class.getClassLoader().getResourceAsStream("test.xml");
Document doc = builder.parse(in);
// root <university>
Element root = doc.getDocumentElement();
if (root == null) return;
//			System.err.println(root.getAttribute("name"));
// all college node
NodeList collegeNodes = root.getChildNodes();
if (collegeNodes == null) return;
System.err.println("university子节点数：" + collegeNodes.getLength());
System.err.println("子节点如下：");
for(int i = 0; i < collegeNodes.getLength(); i++) {
Node college = collegeNodes.item(i);
if (college == null) continue;
if (college.getNodeType() == Node.ELEMENT_NODE) {
System.err.println("\t元素节点：" + college.getNodeName());
} else if (college.getNodeType() == Node.TEXT_NODE) {
System.err.println("\t文本节点：" + Arrays.toString(college.getTextContent().getBytes()));
}
}
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

}
}

输出的结果是：

[java]
view plaincopyprint?

university子节点数：3

子节点如下：
文本节点：[10, 9]

元素节点：college
文本节点：[10]

[html]
view plaincopyprint?

<?xml version="1.0" encoding="UTF-8"?>

<university name="pku">11

<college name="c1">

<class name="class1">

<student name="stu1" sex='male' age="21" />

<student name="stu2" sex='female' age="20" />

<student name="stu3" sex='female' age="20" />

</class>

</college>22

</university>

<?xml version="1.0" encoding="UTF-8"?>
<university name="pku">11
<college name="c1">
<class name="class1">
<student name="stu1" sex='male' age="21" />
<student name="stu2" sex='female' age="20" />
<student name="stu3" sex='female' age="20" />
</class>
</college>22
</university>

还是上面的程序，输出结果为：

[java]
view plaincopyprint?

university子节点数：3

子节点如下：
文本节点：[49, 49, 10, 9]

元素节点：college
文本节点：[50, 50, 10]

university子节点数：3
子节点如下：
文本节点：[49, 49, 10, 9]
元素节点：college
文本节点：[50, 50, 10]其中数字1的ASCII码为49，数字2的ASCII码为50。

2、使用SAX来解析同DOM，当你重写它的public void characters(char[] ch, int start, int length)方法时，你就能看到。

3、JDOM，调用node.getChildren()只返回子节点，不包括TextNode节点（不管该节点是否有Text信息）。如果要获取该节点的Text信息，可以调用node.getText()方法，该方法返回节点的Text信息，也包括\n\t等特殊字符。

4、DOM4j同JDOM

参考：
http://www.docin.com/p-78963650.html http://wenku.baidu.com/view/b091f9360b4c2e3f5727638b.html http://kree.iteye.com/blog/668280