JAVA解析XML的四种方法

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。对于XML本身的语法知识与技
术细节,需要阅读相关的技术文献,这里面包括的内容有DOM(Document Object Model),DTD(Document Type
Definition),SAX(Simple API for XML),XSD(Xml Schema
Definition),XSLT(Extensible Stylesheet Language
Transformations),具体可参阅w3c官方网站文档http://www.w3.org获取更多信息。

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>



本文使用JAVA语言来实现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）。

package com.alisoft.facepay.framework.bean;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

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());

}

}

public void createXml(String fileName) {

Element root = this.document.createElement("employees");

this.document.appendChild(root);

Element employee = this.document.createElement("employee");

Element name = this.document.createElement("name");

name.appendChild(this.document.createTextNode("丁宏亮"));

employee.appendChild(name);

Element sex = this.document.createElement("sex");

sex.appendChild(this.document.createTextNode("m"));

employee.appendChild(sex);

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());

}

}

public void parserXml(String fileName) {

try {

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

DocumentBuilder db = dbf.newDocumentBuilder();

Document document = db.parse(fileName);

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；

package
com.alisoft.facepay.framework.bean;

import
java.io.FileInputStream;

import
java.io.FileNotFoundException;

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.SAXException;

import
org.xml.sax.helpers.DefaultHandler;

/**

*

* @author hongliang.dinghl

* SAX文档解析

*/

public

class
SaxDemo
implements
XmlDocument {

public

void
createXml(String fileName) {

System.out.println("<<"
+filename+
">>"
);

}

public

void
parserXml(String fileName) {

SAXParserFactory saxfac = SAXParserFactory.newInstance();

try
{

SAXParser saxparser = saxfac.newSAXParser();

InputStream is = new
FileInputStream(fileName);

saxparser.parse(is, new
MySAXHandler());

} catch
(ParserConfigurationException e) {

e.printStackTrace();

} catch
(SAXException e) {

e.printStackTrace();

} catch
(FileNotFoundException e) {

e.printStackTrace();

} catch
(IOException e) {

e.printStackTrace();

}

}

}

class
MySAXHandler
extends
DefaultHandler {

boolean
hasAttribute =
false
;

Attributes attributes = null
;

public

void
startDocument()
throws
SAXException {

System.out.println("文档开始打印了"
);

}

public

void
endDocument()
throws
SAXException {

System.out.println("文档打印结束了"
);

}

public

void
startElement(String uri, String localName, String qName,

Attributes attributes) throws
SAXException {

if
(qName.equals(
"employees"
)) {

return
;

}

if
(qName.equals(
"employee"
)) {

System.out.println(qName);

}

if
(attributes.getLength() >
0
) {

this
.attributes = attributes;

this
.hasAttribute =
true
;

}

}

public

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

throws
SAXException {

if
(hasAttribute && (attributes !=
null
)) {

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

System.out.println(attributes.getQName(0
)

+ attributes.getValue(0
));

}

}

}

public

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

throws
SAXException {

System.out.println(new
String(ch, start, length));

}

}