Java解析XML的四种方法

简介

XML现在已经成为一种通用的数据交换格式,它的平台无关性,语言无关性,系统无关性,给数据集成与交互带来了极大的方便。

XML文件解析方法

XML在不同的语言里解析方式都是一样的,只不过实现的语法不同而已。基本的解析方式有两种,一种叫SAX，另一种叫DOM。SAX是基于事件流的解析,DOM是基于XML文档树结构的解析。假设我们XML的内容和结构如下:

<?xml version="1.0" encoding="UTF-8"?>
<employees>
<employee>
<name>ddviplinux</name>
<sex>m</sex>
<age>30</age>
</employee>
</employees>

本文实现DOM与SAX的XML文档生成与解析。

首先定义一个操作XML文档的接口XmlDocument 它定义了XML文档的建立与解析的接口。

package com.alisoft.facepay.framework.bean;

/**
*
* @author hongliang.dinghl
* 定义XML文档建立与解析的接口
*/
public interface XmlDocument {
/**
* 建立XML文档
* @param fileName 文件全路径名称
*/
public void createXml(String fileName);

/**
* 解析XML文档
* @param fileName 文件全路径名称
*/
public void parserXml(String fileName);
}

1.DOM生成和解析XML文档

为 XML 文档的已解析版本定义了一组接口。解析器读入整个文档，然后构建一个驻留内存的树结构，然后代码就可以使用 DOM 接口来操作这个树结构。优点：整个文档树在内存中，便于操作；支持删除、修改、重新排列等多种功能；缺点：将整个文档调入内存（包括无用的节点），浪费时间和空间；使用场合：一旦解析了文档还需多次访问这些数据；硬件资源充足（内存、CPU）。
（1）DOM解析XML文档所使用到的jar：dom.jar

（2）DOM解析与创建XML文档示例代码

package com.alisoft.facepay.framework.bean;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
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.xml.sax.SAXException;

/**
*
* @author hongliang.dinghl DOM生成与解析XML文档
*/
public class DomDemo implements XmlDocument {
private Document document;
private String fileName;

public void init() {
try {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
this.document = builder.newDocument();
} catch(ParserConfigurationException  e) {
System.out.println(e.getMessage());
}
}

//创建一个xml文件
public void createXml(String fileName) {
Element root = this.document.createElement("employees");  //创建一个xml文件根节点
this.document.appendChild(root); //把根节点加到xml文档结构下面
Element employee = this.document.createElement("employee"); //创过employee节点
Element name = this.document.createElement("name"); //创建name节点
name.appendChild(this.document.createTextNode("丁宏亮")); //创建一个内容,并把内容加到name节点下面
employee.appendChild(name);  //把name加到employee下面
Element sex = this.document.createElement("sex"); //创建军一个sex节点
sex.appendChild(this.document.createTextNode("m")); //创建一个性别添加到性别节点下面
employee.appendChild(sex); //把性别添加到,人员节点下面
Element age = this.document.createElement("age");
age.appendChild(this.document.createTextNode("30"));
employee.appendChild(age);
root.appendChild(employee);
TransformerFactory tf = TransformerFactory.newInstance();
try {
Transformer transformer = tf.newTransformer();
DOMSource source = new DOMSource(document);
transformer.setOutputProperty(OutputKeys.ENCODING, "gb2312");
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
PrintWriter pw = new PrintWriter(new FileOutputStream(fileName));
StreamResult result = new StreamResult(pw);
transformer.transform(source, result);
System.out.println("生成XML文件成功!");
} catch (TransformerConfigurationException e) {
System.out.println(e.getMessage());
} catch (IllegalArgumentException e) {
System.out.println(e.getMessage());
} catch (FileNotFoundException e) {
System.out.println(e.getMessage());
} catch (TransformerException e) {
System.out.println(e.getMessage());
}

}

//解释一个XML文件
public void parserXml(String fileName) {
try {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document document = db.parse(fileName); // 读取xml文件
NodeList employees = document.getChildNodes();

for (int i = 0; i < employees.getLength(); i++) {
Node employee = employees.item(i);
NodeList employeeInfo = employee.getChildNodes();
for (int j = 0; j < employeeInfo.getLength(); j++) {
Node node = employeeInfo.item(j);
NodeList employeeMeta = node.getChildNodes();
for (int k = 0; k < employeeMeta.getLength(); k++) {
System.out.println(employeeMeta.item(k).getNodeName()
+ ":" + employeeMeta.item(k).getTextContent());
}
}
}

System.out.println("解析完毕");
} catch (FileNotFoundException e) {
System.out.println(e.getMessage());
} catch (ParserConfigurationException e) {
System.out.println(e.getMessage());
} catch (SAXException e) {
System.out.println(e.getMessage());
} catch (IOException e) {
System.out.println(e.getMessage());
}
}

}

2.SAX生成和解析XML文档

为解决DOM的问题，出现了SAX。SAX ，事件驱动。当解析器发现元素开始、元素结束、文本、文档的开始或结束等时，发送事件，程序员编写响应这些事件的代码，保存数据。优点：不用事先调入整个文档，占用资源少；SAX解析器代码比DOM解析器代码小，适于Applet，下载。缺点：不是持久的；事件过后，若没保存数据，那么数据就丢了；无状态性；从事件中只能得到文本，但不知该文本属于哪个元素；使用场合：Applet;只需XML文档的少量内容，很少回头访问；机器内存少；
（1）SAX解析XML文档所使用到的jar包：sax.jar

（2）SAX关健类的，类结构图



（3）SAX文档解释示例代码

package com.alisoft.facepay.framework.bean;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.XMLReaderFactory;

public class XMLParser {
protected PrintStream output = new PrintStream(new BufferedOutputStream(
new FileOutputStream(java.io.FileDescriptor.out), 128), true);
// handler error info.
protected PrintStream error = new PrintStream(new BufferedOutputStream(
new FileOutputStream(java.io.FileDescriptor.err), 128), true);

public void parserXMLFile(String fileName) throws SAXException, IOException {
XMLReader reader = XMLReaderFactory.createXMLReader();
reader.setContentHandler(new MyContentHandler());
reader.setErrorHandler(new MyErrorHandler());
InputSource source = new InputSource(new FileInputStream(new File(
fileName)));
reader.parse(source);
}

class MyErrorHandler implements ErrorHandler {

public void error(SAXParseException exception) throws SAXException {

error.println(exception.getMessage());
}

public void fatalError(SAXParseException exception) throws SAXException {

error.println(exception.getMessage());
}

public void warning(SAXParseException exception) throws SAXException {
output.println(exception.getMessage());

}

}

class MyContentHandler implements ContentHandler {

private StringBuffer buffer = new StringBuffer();
private String key;

public void characters(char[] ch, int start, int length)
throws SAXException {
buffer.append(ch, start, length); // 添加标记中间的内容

}

public void endDocument() throws SAXException {

}

public void endElement(String uri, String localName, String name)
throws SAXException {
if (key.equals(localName)) {
output.print(buffer); // 输出标记中间的内容
}
output.print("</" + localName + ">");
}

public void endPrefixMapping(String prefix) throws SAXException {
}

public void ignorableWhitespace(char[] ch, int start, int length)
throws SAXException {
}

public void processingInstruction(String target, String data)
throws SAXException {
}

public void setDocumentLocator(Locator locator) {
}

public void skippedEntity(String name) throws SAXException {
}

public void startDocument() throws SAXException // XML文档开始读取时调用
{
output.println("<xml version=\"1.0\" encoding=\"utf-8\"?>");
}

public void startElement(String uri, String localName, String name,
Attributes atts) throws SAXException // 获取标记开始信息
{
// uri is identifier of namespace
// name-->prefix:localName

buffer.delete(0, buffer.length());
key = localName;

output.print("<" + localName);
for (int i = 0; i < atts.getLength(); i++) {
String attrName = atts.getLocalName(i);
String attrValue = atts.getValue(i);
output.print(" " + attrName + "=" + attrValue);
}
output.print(">" + "\r");
}

public void startPrefixMapping(String prefix, String uri)
throws SAXException {
}
}

public static void main(String[] args) throws Exception, IOException {
XMLParser parser = new XMLParser();
parser.parserXMLFile("D:/testSpace/testPrj/src/xmlPackage/MyXml.xml"); // 解释XML文件
}
}

（4）SAX生成XML文档示例代码(生成XML)

package com.alisoft.facepay.framework.bean;

import java.io.FileOutputStream;
import java.io.StringWriter;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.sax.SAXTransformerFactory;
import javax.xml.transform.sax.TransformerHandler;
import javax.xml.transform.stream.StreamResult;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.AttributesImpl;

public class XMLHandler {
public String createXMLFile() {
String xmlStr = null;
try {
Result resultXml = new StreamResult(new FileOutputStream(
"E://cities.xml"));
StringWriter writerStr = new StringWriter();
SAXTransformerFactory sff = (SAXTransformerFactory) SAXTransformerFactory
.newInstance();
TransformerHandler th = sff.newTransformerHandler();
Transformer transformer = th.getTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
th.setResult(resultXml);
th.startDocument();
String four = "\n    ";
String eight = "\n        ";
AttributesImpl attr = new AttributesImpl();
th.startElement("", "", "country", attr);
th.characters(four.toCharArray(), 0, four.length());

th.startElement("", "", "china", attr);

th.characters(eight.toCharArray(), 0, eight.length());

th.startElement("", "", "city", attr);
String bj = "Beijing";
th.characters(bj.toCharArray(), 0, bj.length());
th.endElement("", "", "city");

th.characters(eight.toCharArray(), 0, eight.length());

th.startElement("", "", "city", attr);
String sh = "Shanghai";
th.characters(sh.toCharArray(), 0, sh.length());
th.endElement("", "", "city");

th.characters(four.toCharArray(), 0, four.length());

th.endElement("", "", "china");
th.endElement("", "", "country");
th.endDocument();
xmlStr = writerStr.getBuffer().toString();
} catch (TransformerConfigurationException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
return xmlStr;
}

public static void main(String args[]) {
XMLHandler xh = new XMLHandler();
xh.createXMLFile();
}
}

生成的XML文档：

<?xml version="1.0" encoding="UTF-8" ?>
<country>
<china>
<city>Beijing</city>
<city>Shanghai</city>
</china>
</country>

3.DOM4J生成和解析XML文档

DOM4J 是一个非常非常优秀的Java XML API，具有性能优异、功能强大和极端易用使用的特点，同时它也是一个开放源代码的软件。如今你可以看到越来越多的 Java 软件都在使用 DOM4J 来读写 XML，特别值得一提的是连 Sun 的JAXM 也在用 DOM4J。
（1）Dom4j解析XML文档所使用到的jar包：dom4j.jar
（2）Dom4j文档解释示例代码

package com.alisoft.facepay.framework.bean;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.util.Iterator;

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

/**
*
* @author hongliang.dinghl Dom4j 生成XML文档与解析XML文档
*/
public class Dom4jDemo implements XmlDocument {

// Dom4j创建Xml文档
public void createXml(String fileName) {
Document document = DocumentHelper.createDocument(); // 创建一个文档对象
Element employees = document.addElement("employees"); // 在根节点添加元素
Element employee = employees.addElement("employee"); // 在employees下添加子节点
Element name = employee.addElement("name"); // 在employee下添加子节点
name.setText("ddvip"); // 给name节点添加内容
Element sex = employee.addElement("sex");
sex.setText("m");
Element age = employee.addElement("age");
age.setText("29");
try {
Writer fileWriter = new FileWriter(fileName);
XMLWriter xmlWriter = new XMLWriter(fileWriter);
xmlWriter.write(document);
xmlWriter.close();
} catch (IOException e) {

System.out.println(e.getMessage());
}

}

// Dom4j解释Xml文档
public void parserXml(String fileName) {
File inputXml = new File(fileName);
SAXReader saxReader = new SAXReader();
try {
Document document = saxReader.read(inputXml);
Element employees = document.getRootElement();
for (Iterator i = employees.elementIterator(); i.hasNext();) {
Element employee = (Element) i.next();
for (Iterator j = employee.elementIterator(); j.hasNext();) { // 遍例节点
Element node = (Element) j.next();
System.out.println(node.getName() + ":" + node.getText());
}

}
} catch (DocumentException e) {
System.out.println(e.getMessage());
}
System.out.println("dom4j parserXml");
}
}

4.JDOM生成和解析XML

为减少DOM、SAX的编码量，出现了JDOM；优点：20-80原则，极大减少了代码量。使用场合：要实现的功能简单，如解析、创建等，但在底层，JDOM还是使用SAX（最常用）、DOM、Xanan文档。
（1）JDOM解析XML文档所使用到的jar包：jdom.jar（2）JDOM文档解释示例代码

package com.alisoft.facepay.framework.bean;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.List;

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

/**
*
* @author hongliang.dinghl JDOM 生成与解析XML文档
*
*/
public class JDomDemo implements XmlDocument {

public void createXml(String fileName) {
Document document;
Element root;
root = new Element("employees");
document = new Document(root);
Element employee = new Element("employee");
root.addContent(employee);
Element name = new Element("name");
name.setText("ddvip");
employee.addContent(name);
Element sex = new Element("sex");
sex.setText("m");
employee.addContent(sex);
Element age = new Element("age");
age.setText("23");
employee.addContent(age);
XMLOutputter XMLOut = new XMLOutputter();
try {
XMLOut.output(document, new FileOutputStream(fileName));
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

public void parserXml(String fileName) {
SAXBuilder builder = new SAXBuilder(false);
try {
Document document = builder.build(fileName);
Element employees = document.getRootElement();
List employeeList = employees.getChildren();
// 获取employee节点
for (int i = 0; i < employeeList.size(); i++) {
Element employee = (Element) employeeList.get(i);
List employeeInfo = employee.getChildren();
// 获取employee节点下面的所有子节点
for(int j = 0; j < employeeInfo.size(); j++) {
Element info = (Element)employeeInfo.get(j);
System.out.println(info.getName() + ":" + info.getValue());
}
}
} catch (JDOMException  e) {
System.out.println(e.getMessage());
} catch (IOException e) {
System.out.println(e.getMessage());
}
}
}

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