1、基础知识：
Java解析XML一般有四种方法：DOM、SAX、JDOM、DOM4J。
2、使用介绍
1)、DOM
(1)简介
由W3C(org.w3c.dom)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。优点就是整个文档都一直在内存中，我们可以随时访问任何节点，并且对树的遍历也是比较熟悉的操作；缺点则是耗内存，并且必须等到所有的文档都读入内存才能进行处理。
(2)示例代码：
599 CMCC 699 ChinaNet
import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.StringReader; 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.xml.sax.InputSource; import org.xml.sax.SAXException; public class XMLHandler { public XMLHandler(){ } public String createXML(){ String xmlStr = null; DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); try { DocumentBuilder builder = factory.newDocumentBuilder(); Document document = builder.newDocument(); document.setXmlVersion("1.0"); Element root = document.createElement("root"); document.appendChild(root); Element telephone = document.createElement("TelePhone"); Element nokia = document.createElement("type"); nokia.setAttribute("name", "nokia"); Element priceNokia = document.createElement("price"); priceNokia.setTextContent("599"); nokia.appendChild(priceNokia); Element operatorNokia = document.createElement("operator"); operatorNokia.setTextContent("CMCC"); nokia.appendChild(operatorNokia); telephone.appendChild(nokia); Element xiaomi = document.createElement("type"); xiaomi.setAttribute("name", "xiaomi"); Element priceXiaoMi = document.createElement("price"); priceXiaoMi.setTextContent("699"); xiaomi.appendChild(priceXiaoMi); Element operatorXiaoMi = document.createElement("operator"); operatorXiaoMi.setTextContent("ChinaNet"); xiaomi.appendChild(operatorXiaoMi); telephone.appendChild(xiaomi); root.appendChild(telephone); TransformerFactory transFactory = TransformerFactory.newInstance(); Transformer transFormer = transFactory.newTransformer(); DOMSource domSource = new DOMSource(document); //export string ByteArrayOutputStream bos = new ByteArrayOutputStream(); transFormer.transform(domSource, new StreamResult(bos)); xmlStr = bos.toString(); //------- //save as file File file = new File("TelePhone.xml"); if(!file.exists()){ file.createNewFile(); } FileOutputStream out = new FileOutputStream(file); StreamResult xmlResult = new StreamResult(out); transFormer.transform(domSource, xmlResult); //-------- } catch (ParserConfigurationException e) { // TODO Auto-generated catch block e.printStackTrace(); }catch (TransformerConfigurationException e) { // TODO Auto-generated catch block e.printStackTrace(); }catch (TransformerException e) { // TODO Auto-generated catch block e.printStackTrace(); }catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return xmlStr; } public void parserXML(String strXML){ DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); try { DocumentBuilder builder = factory.newDocumentBuilder(); StringReader sr = new StringReader(strXML); InputSource is = new InputSource(sr); Document doc = builder.parse(is); Element rootElement = doc.getDocumentElement(); NodeList phones = rootElement.getElementsByTagName("type"); for (int i = 0; i < phones.getLength(); i++) { Node type = phones.item(i); String phoneName = ((Element)type).getAttribute("name"); System.out.println("Phone name = "+phoneName); NodeList properties = type.getChildNodes(); for (int j = 0; j < properties.getLength(); j++) { Node property = properties.item(j); String nodeName = property.getNodeName(); if (nodeName.equals("price")) { String price=property.getFirstChild().getNodeValue(); System.out.println("price="+price); } else if (nodeName.equals("operator")) { String operator=property.getFirstChild().getNodeValue(); System.out.println("operator="+operator); } } } } catch (ParserConfigurationException e) { // TODO Auto-generated catch block e.printStackTrace(); }catch (SAXException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public static void main(String[] args) { XMLHandler handler = new XMLHandler(); String xml = handler.createXML(); System.out.println(xml); handler.parserXML(xml); } }
(3)元素(Element)和结点(Node)的区别（org.w3c.dom）
Node对象是整个文档对象模型的主要数据类型，是DOM中最基本的对象，代表了文档树中的抽象节点。但在实际使用中很少会直接使用Node对象，而是使用Node对象的子对象Element,Attr,Text等。
Element对象表示HTML或XML文档中的一个元素，是Node类最主要的子对象，在元素中可以包含属性，因而Element中有存取其属性的方法。
Element是从Node继承而来的，元素是一个小范围的定义，必须是含有完整信息的结点才是一个元素，例如
2)、SAX
3)、JDOM
4)、DOM4J
(1)简介
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。
在使用XPATH时要增加jaxen.jar，否则会出现如下错误：
Exception in thread "main" java.lang.NoClassDefFoundError: org/jaxen/JaxenException at org.dom4j.DocumentFactory.createXPath(DocumentFactory.java:230) at org.dom4j.tree.AbstractNode.createXPath(AbstractNode.java:207) at org.dom4j.tree.AbstractNode.selectNodes(AbstractNode.java:164)
(2)示例代码：
import java.io.File; import java.io.FileWriter; import java.io.IOException; import java.io.StringReader; import java.io.StringWriter; import java.util.List; 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.SAXReader; import org.dom4j.io.XMLWriter; import org.xml.sax.InputSource; public class XMLHandler { public XMLHandler() { // TODO Auto-generated constructor stub } public String createXML(){ String strXML = null; Document document = DocumentHelper.createDocument(); Element root = document.addElement("root"); Element phone = root.addElement("TelePhone"); Element nokia = phone.addElement("type"); nokia.addAttribute("name", "nokia"); Element price_nokia = nokia.addElement("price"); price_nokia.addText("599"); Element operator_nokia = nokia.addElement("operator"); operator_nokia.addText("CMCC"); Element xiaomi = phone.addElement("type"); xiaomi.addAttribute("name", "xiaomi"); Element price_xiaomi = xiaomi.addElement("price"); price_xiaomi.addText("699"); Element operator_xiaomi = xiaomi.addElement("operator"); operator_xiaomi.addText("ChinaNet"); //-------- StringWriter strWtr = new StringWriter(); OutputFormat format = OutputFormat.createPrettyPrint(); format.setEncoding("UTF-8"); XMLWriter xmlWriter =new XMLWriter(strWtr, format); try { xmlWriter.write(document); } catch (IOException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } strXML = strWtr.toString(); //-------- //------- //strXML=document.asXML(); //------ //------------- File file = new File("TelePhone.xml"); if (file.exists()) { file.delete(); } try { file.createNewFile(); XMLWriter out = new XMLWriter(new FileWriter(file)); out.write(document); out.flush(); out.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } //-------------- return strXML; } public void parserXML(String strXML){ SAXReader reader = new SAXReader(); StringReader sr = new StringReader(strXML); InputSource is = new InputSource(sr); try { Document document = reader.read(is); Element root = document.getRootElement(); //get element List phoneList = root.elements("TelePhone"); List typeList = phoneList.get(0).elements("type"); for (int i=0;i
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5)XPATH
(1)简介
XPath是一门在XML文档中查找信息的语言。XPath用于在XML文档中通过元素和属性进行导航。
具体语法介绍参考：http://w3school.com.cn/xpath/index.asp
(2)示例代码：
import java.io.IOException; import java.io.StringReader; 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.Element; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.xml.sax.InputSource; import org.xml.sax.SAXException; public class XMLHandler { public XMLHandler() { // TODO Auto-generated constructor stub } public void parserXML(String strXML){ DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); try { DocumentBuilder builder = factory.newDocumentBuilder(); StringReader sr = new StringReader(strXML); InputSource is = new InputSource(sr); Document doc = builder.parse(is); XPathFactory xFactory = XPathFactory.newInstance(); XPath xpath = xFactory.newXPath(); XPathExpression expr = xpath.compile("/root/TelePhone/type"); NodeList phones = (NodeList) expr.evaluate(doc, XPathConstants.NODESET); for (int i = 0; i < phones.getLength(); i++) { Node type = phones.item(i); String phoneName = ((Element)type).getAttribute("name"); System.out.println("Phone name = "+phoneName); XPathExpression expr1 = xpath.compile("./*"); NodeList list = (NodeList) expr1.evaluate(type, XPathConstants.NODESET); for(int j =0;j"+ ""+ ""+ ""+ "599 "+ "CMCC "+ " "+ ""+ "699 "+ "ChinaNet "+ " "+ " "+ " "; XMLHandler handler = new XMLHandler(); handler.parserXML(strXML); } }
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