XML現在已經(jīng)成為一種通用的數據交換格式,它的平臺無(wú)關(guān)性,語(yǔ)言無(wú)關(guān)性,系統無(wú)關(guān)性,給數據集成與交互帶來(lái)了極大的方便。對于XML本身的語(yǔ)法知識與技術(shù)細節,需要閱讀相關(guān)的技術(shù)文獻,這里面包括的內容有DOM(Document Object Model),DTD(Document Type Definition),SAX(Simple API for XML),XSD(Xml Schema Definition),XSLT(Extensible Stylesheet Language Transformations),具體可參閱w3c官方網(wǎng)站文檔http://www.w3.org獲取更多信息。
XML在不同的語(yǔ)言里解析方式都是一樣的,只不過(guò)實(shí)現的語(yǔ)法不同而已?；镜慕馕龇绞接袃煞N,一種叫SAX，另一種叫DOM。SAX是基于事件流的解析,DOM是基于XML文檔樹(shù)結構的解析。假設我們XML的內容和結構如下:
<?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語(yǔ)言來(lái)實(shí)現DOM與SAX的XML文檔生成與解析。
首先定義一個(gè)操作XML文檔的接口XmlDocument 它定義了XML文檔的建立與解析的接口。
package com.alisoft.facepay.framework.bean;
/**
*
* @author hongliang.dinghl
* 定義XML文檔建立與解析的接口
*/
public interface XmlDocument {
/**
* 建立XML文檔
* @param fileName 文件全路徑名稱(chēng)
*/
public void createXml(String fileName);
/**
* 解析XML文檔
* @param fileName 文件全路徑名稱(chēng)
*/
public void parserXml(String fileName);
}
1. DOM生成和解析XML文檔
為 XML 文檔的已解析版本定義了一組接口。解析器讀入整個(gè)文檔，然后構建一個(gè)駐留內存的樹(shù)結構，然后代碼就可以使用 DOM 接口來(lái)操作這個(gè)樹(shù)結構。優(yōu)點(diǎn)：整個(gè)文檔樹(shù)在內存中，便于操作；支持刪除、修改、重新排列等多種功能；缺點(diǎn)：將整個(gè)文檔調入內存（包括無(wú)用的節點(diǎn)），浪費時(shí)間和空間；使用場(chǎng)合：一旦解析了文檔還需多次訪(fǎng)問(wèn)這些數據；硬件資源充足（內存、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生成與解析XML文檔
*/
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(“解析完畢“);
} 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文檔
為解決DOM的問(wèn)題，出現了SAX。SAX ，事件驅動(dòng)。當解析器發(fā)現元素開(kāi)始、元素結束、文本、文檔的開(kāi)始或結束等時(shí)，發(fā)送事件，程序員編寫(xiě)響應這些事件的代碼，保存數據。優(yōu)點(diǎn)：不用事先調入整個(gè)文檔，占用資源少；SAX解析器代碼比DOM解析器代碼小，適于A(yíng)pplet，下載。缺點(diǎn)：不是持久的；事件過(guò)后，若沒(méi)保存數據，那么數據就丟了；無(wú)狀態(tài)性；從事件中只能得到文本，但不知該文本屬于哪個(gè)元素；使用場(chǎng)合：Applet;只需XML文檔的少量?jì)热?，很少回頭訪(fǎng)問(wèn)；機器內存少；
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文檔解析
*/
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(“文檔開(kāi)始打印了“);
}
public void endDocument() throws SAXException {
System.out.println(“文檔打印結束了“);
}
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));
}
}
3. DOM4J生成和解析XML文檔
DOM4J 是一個(gè)非常非常優(yōu)秀的Java XML API，具有性能優(yōu)異、功能強大和極端易用使用的特點(diǎn)，同時(shí)它也是一個(gè)開(kāi)放源代碼的軟件。如今你可以看到越來(lái)越多的 Java 軟件都在使用 DOM4J 來(lái)讀寫(xiě) XML，特別值得一提的是連 Sun 的 JAXM 也在用 DOM4J。
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文檔與解析XML文檔
*/
public class Dom4jDemo implements XmlDocument {
public void createXml(String fileName) {
Document document = DocumentHelper.createDocument();
Element employees=document.addElement(“employees”);
Element employee=employees.addElement(“employee”);
Element name= employee.addElement(“name”);
name.setText(“ddvip”);
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());
}
}
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();){
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
為減少DOM、SAX的編碼量，出現了JDOM；優(yōu)點(diǎn)：20-80原則，極大減少了代碼量。使用場(chǎng)合：要實(shí)現的功能簡(jiǎn)單，如解析、創(chuàng )建等，但在底層，JDOM還是使用SAX（最常用）、DOM、Xanan文檔。
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 生成與解析XML文檔
*
*/
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(“employee”);
for(int i=0;i<employeeList.size();i++){
Element employee=(Element)employeeList.get(i);
List employeeInfo=employee.getChildren();
for(int j=0;j<employeeInfo.size();j++){
System.out.println(((Element)employeeInfo.get(j)).getName()+“:”+((Element)employeeInfo.get(j)).getValue());
}
}
} catch (JDOMException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
