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"?> |
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; |
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 package com.alisoft.facepay.framework.bean; 2 import java.io.FileInputStream; 3 import java.io.FileNotFoundException; 4 import java.io.FileOutputStream; 5 import java.io.IOException; 6 import java.io.InputStream; 7 import java.io.PrintWriter; 8 import javax.xml.parsers.DocumentBuilder; 9 import javax.xml.parsers.DocumentBuilderFactory; 10 import javax.xml.parsers.ParserConfigurationException; 11 import javax.xml.transform.OutputKeys; 12 import javax.xml.transform.Transformer; 13 import javax.xml.transform.TransformerConfigurationException; 14 import javax.xml.transform.TransformerException; 15 import javax.xml.transform.TransformerFactory; 16 import javax.xml.transform.dom.DOMSource; 17 import javax.xml.transform.stream.StreamResult; 18 import org.w3c.dom.Document; 19 import org.w3c.dom.Element; 20 import org.w3c.dom.Node; 21 import org.w3c.dom.NodeList; 22 import org.xml.sax.SAXException; 23 /** 24 * 25 * @author hongliang.dinghl 26 * DOM生成与解析XML文档 27 */ 28 public class DomDemo implements XmlDocument { 29 private Document document; 30 private String fileName; 31 public void init() { 32 try { 33 DocumentBuilderFactory factory = DocumentBuilderFactory 34 .newInstance(); 35 DocumentBuilder builder = factory.newDocumentBuilder(); 36 this.document = builder.newDocument(); 37 } catch (ParserConfigurationException e) { 38 System.out.println(e.getMessage()); 39 } 40 } 41 public void createXml(String fileName) { 42 Element root = this.document.createElement("employees"); 43 this.document.appendChild(root); 44 Element employee = this.document.createElement("employee"); 45 Element name = this.document.createElement("name"); 46 name.appendChild(this.document.createTextNode("丁宏亮")); 47 employee.appendChild(name); 48 Element sex = this.document.createElement("sex"); 49 sex.appendChild(this.document.createTextNode("m")); 50 employee.appendChild(sex); 51 Element age = this.document.createElement("age"); 52 age.appendChild(this.document.createTextNode("30")); 53 employee.appendChild(age); 54 root.appendChild(employee); 55 TransformerFactory tf = TransformerFactory.newInstance(); 56 try { 57 Transformer transformer = tf.newTransformer(); 58 DOMSource source = new DOMSource(document); 59 transformer.setOutputProperty(OutputKeys.ENCODING, "gb2312"); 60 transformer.setOutputProperty(OutputKeys.INDENT, "yes"); 61 PrintWriter pw = new PrintWriter(new FileOutputStream(fileName)); 62 StreamResult result = new StreamResult(pw); 63 transformer.transform(source, result); 64 System.out.println("生成XML文件成功!"); 65 } catch (TransformerConfigurationException e) { 66 System.out.println(e.getMessage()); 67 } catch (IllegalArgumentException e) { 68 System.out.println(e.getMessage()); 69 } catch (FileNotFoundException e) { 70 System.out.println(e.getMessage()); 71 } catch (TransformerException e) { 72 System.out.println(e.getMessage()); 73 } 74 } 75 public void parserXml(String fileName) { 76 try { 77 DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); 78 DocumentBuilder db = dbf.newDocumentBuilder(); 79 Document document = db.parse(fileName); 80 NodeList employees = document.getChildNodes(); 81 for (int i = 0; i < employees.getLength(); i++) { 82 Node employee = employees.item(i); 83 NodeList employeeInfo = employee.getChildNodes(); 84 for (int j = 0; j < employeeInfo.getLength(); j++) { 85 Node node = employeeInfo.item(j); 86 NodeList employeeMeta = node.getChildNodes(); 87 for (int k = 0; k < employeeMeta.getLength(); k++) { 88 System.out.println(employeeMeta.item(k).getNodeName() 89 + ":" + employeeMeta.item(k).getTextContent()); 90 } 91 } 92 } 93 System.out.println("解析完毕"); 94 } catch (FileNotFoundException e) { 95 System.out.println(e.getMessage()); 96 } catch (ParserConfigurationException e) { 97 System.out.println(e.getMessage()); 98 } catch (SAXException e) { 99 System.out.println(e.getMessage()); 100 } catch (IOException e) { 101 System.out.println(e.getMessage()); 102 } 103 } 104 }
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；
Java代码
1 package com.alisoft.facepay.framework.bean; 2 import java.io.FileInputStream; 3 import java.io.FileNotFoundException; 4 import java.io.IOException; 5 import java.io.InputStream; 6 7 import javax.xml.parsers.ParserConfigurationException; 8 import javax.xml.parsers.SAXParser; 9 import javax.xml.parsers.SAXParserFactory; 10 11 import org.xml.sax.Attributes; 12 import org.xml.sax.SAXException; 13 import org.xml.sax.helpers.DefaultHandler; 14 /** 15 * 16 * @author hongliang.dinghl 17 * SAX文档解析 18 */ 19 public class SaxDemo implements XmlDocument { 20 21 public void createXml(String fileName) { 22 System.out.println("<<"+filename+">>"); 23 } 24 25 public void parserXml(String fileName) { 26 SAXParserFactory saxfac = SAXParserFactory.newInstance(); 27 28 try { 29 30 SAXParser saxparser = saxfac.newSAXParser(); 31 32 InputStream is = new FileInputStream(fileName); 33 34 saxparser.parse(is, new MySAXHandler()); 35 36 } catch (ParserConfigurationException e) { 37 38 e.printStackTrace(); 39 40 } catch (SAXException e) { 41 42 e.printStackTrace(); 43 44 } catch (FileNotFoundException e) { 45 46 e.printStackTrace(); 47 48 } catch (IOException e) { 49 50 e.printStackTrace(); 51 52 } 53 54 } 55 56 } 57 58 class MySAXHandler extends DefaultHandler { 59 60 boolean hasAttribute = false; 61 62 Attributes attributes = null; 63 64 public void startDocument() throws SAXException { 65 66 System.out.println("文档开始打印了"); 67 68 } 69 70 public void endDocument() throws SAXException { 71 72 System.out.println("文档打印结束了"); 73 74 } 75 76 public void startElement(String uri, String localName, String qName, 77 78 Attributes attributes) throws SAXException { 79 80 if (qName.equals("employees")) { 81 82 return; 83 84 } 85 86 if (qName.equals("employee")) { 87 88 System.out.println(qName); 89 90 } 91 92 if (attributes.getLength() > 0) { 93 94 this.attributes = attributes; 95 96 this.hasAttribute = true; 97 98 } 99 100 } 101 102 public void endElement(String uri, String localName, String qName) 103 104 throws SAXException { 105 106 if (hasAttribute && (attributes != null)) { 107 108 for (int i = 0; i < attributes.getLength(); i++) { 109 110 System.out.println(attributes.getQName(0) 111 + attributes.getValue(0)); 112 113 } 114 115 } 116 117 } 118 119 public void characters(char[] ch, int start, int length) 120 121 throws SAXException { 122 123 System.out.println(new String(ch, start, length)); 124 125 } 126 127 }
1 package com.alisoft.facepay.framework.bean; 2 import java.io.FileInputStream; 3 import java.io.FileNotFoundException; 4 import java.io.IOException; 5 import java.io.InputStream; 6 import javax.xml.parsers.ParserConfigurationException; 7 import javax.xml.parsers.SAXParser; 8 import javax.xml.parsers.SAXParserFactory; 9 import org.xml.sax.Attributes; 10 import org.xml.sax.SAXException; 11 import org.xml.sax.helpers.DefaultHandler; 12 /** 13 * 14 * @author hongliang.dinghl 15 * SAX文档解析 16 */ 17 public class SaxDemo implements XmlDocument { 18 public void createXml(String fileName) { 19 System.out.println("<<"+filename+">>"); 20 } 21 public void parserXml(String fileName) { 22 SAXParserFactory saxfac = SAXParserFactory.newInstance(); 23 try { 24 SAXParser saxparser = saxfac.newSAXParser(); 25 InputStream is = new FileInputStream(fileName); 26 saxparser.parse(is, new MySAXHandler()); 27 } catch (ParserConfigurationException e) { 28 e.printStackTrace(); 29 } catch (SAXException e) { 30 e.printStackTrace(); 31 } catch (FileNotFoundException e) { 32 e.printStackTrace(); 33 } catch (IOException e) { 34 e.printStackTrace(); 35 } 36 } 37 } 38 class MySAXHandler extends DefaultHandler { 39 boolean hasAttribute = false; 40 Attributes attributes = null; 41 public void startDocument() throws SAXException { 42 System.out.println("文档开始打印了"); 43 } 44 public void endDocument() throws SAXException { 45 System.out.println("文档打印结束了"); 46 } 47 public void startElement(String uri, String localName, String qName, 48 Attributes attributes) throws SAXException { 49 if (qName.equals("employees")) { 50 return; 51 } 52 if (qName.equals("employee")) { 53 System.out.println(qName); 54 } 55 if (attributes.getLength() > 0) { 56 this.attributes = attributes; 57 this.hasAttribute = true; 58 } 59 } 60 public void endElement(String uri, String localName, String qName) 61 throws SAXException { 62 if (hasAttribute && (attributes != null)) { 63 for (int i = 0; i < attributes.getLength(); i++) { 64 System.out.println(attributes.getQName(0) 65 + attributes.getValue(0)); 66 } 67 } 68 } 69 public void characters(char[] ch, int start, int length) 70 throws SAXException { 71 System.out.println(new String(ch, start, length)); 72 } 73 }
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。
Java代码
1 package com.alisoft.facepay.framework.bean; 2 import java.io.File; 3 import java.io.FileWriter; 4 import java.io.IOException; 5 import java.io.Writer; 6 import java.util.Iterator; 7 8 import org.dom4j.Document; 9 import org.dom4j.DocumentException; 10 import org.dom4j.DocumentHelper; 11 import org.dom4j.Element; 12 import org.dom4j.io.SAXReader; 13 import org.dom4j.io.XMLWriter; 14 /** 15 * 16 * @author hongliang.dinghl 17 * Dom4j 生成XML文档与解析XML文档 18 */ 19 public class Dom4jDemo implements XmlDocument { 20 21 public void createXml(String fileName) { 22 Document document = DocumentHelper.createDocument(); 23 Element employees=document.addElement("employees"); 24 Element employee=employees.addElement("employee"); 25 Element name= employee.addElement("name"); 26 name.setText("ddvip"); 27 Element sex=employee.addElement("sex"); 28 sex.setText("m"); 29 Element age=employee.addElement("age"); 30 age.setText("29"); 31 try { 32 Writer fileWriter=new FileWriter(fileName); 33 XMLWriter xmlWriter=new XMLWriter(fileWriter); 34 xmlWriter.write(document); 35 xmlWriter.close(); 36 } catch (IOException e) { 37 38 System.out.println(e.getMessage()); 39 } 40 41 42 } 43 44 45 public void parserXml(String fileName) { 46 File inputXml=new File(fileName); 47 SAXReader saxReader = new SAXReader(); 48 try { 49 Document document = saxReader.read(inputXml); 50 Element employees=document.getRootElement(); 51 for(Iterator i = employees.elementIterator(); i.hasNext();){ 52 Element employee = (Element) i.next(); 53 for(Iterator j = employee.elementIterator(); j.hasNext();){ 54 Element node=(Element) j.next(); 55 System.out.println(node.getName()+":"+node.getText()); 56 } 57 58 } 59 } catch (DocumentException e) { 60 System.out.println(e.getMessage()); 61 } 62 System.out.println("dom4j parserXml"); 63 } 64 }
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 package com.alisoft.facepay.framework.bean; 2 3 import java.io.FileNotFoundException; 4 import java.io.FileOutputStream; 5 import java.io.IOException; 6 import java.util.List; 7 8 import org.jdom.Document; 9 import org.jdom.Element; 10 import org.jdom.JDOMException; 11 import org.jdom.input.SAXBuilder; 12 import org.jdom.output.XMLOutputter; 13 /** 14 * 15 * @author hongliang.dinghl 16 * JDOM 生成与解析XML文档 17 * 18 */ 19 public class JDomDemo implements XmlDocument { 20 21 public void createXml(String fileName) { 22 Document document; 23 Element root; 24 root=new Element("employees"); 25 document=new Document(root); 26 Element employee=new Element("employee"); 27 root.addContent(employee); 28 Element name=new Element("name"); 29 name.setText("ddvip"); 30 employee.addContent(name); 31 Element sex=new Element("sex"); 32 sex.setText("m"); 33 employee.addContent(sex); 34 Element age=new Element("age"); 35 age.setText("23"); 36 employee.addContent(age); 37 XMLOutputter XMLOut = new XMLOutputter(); 38 try { 39 XMLOut.output(document, new FileOutputStream(fileName)); 40 } catch (FileNotFoundException e) { 41 e.printStackTrace(); 42 } catch (IOException e) { 43 e.printStackTrace(); 44 } 45 46 } 47 48 public void parserXml(String fileName) { 49 SAXBuilder builder=new SAXBuilder(false); 50 try { 51 Document document=builder.build(fileName); 52 Element employees=document.getRootElement(); 53 List employeeList=employees.getChildren("employee"); 54 for(int i=0;i<employeelist.size();i++){ <br="">Element employee=(Element)employeeList.get(i); 55 List employeeInfo=employee.getChildren(); 56 for(int j=0;j<employeeinfo.size();j++){ <br="">System.out.println(((Element)employeeInfo.get(j)).getName()+":"+((Element)employeeInfo.get(j)).getValue()); 57 58 } 59 } 60 } catch (JDOMException e) { 61 62 e.printStackTrace(); 63 } catch (IOException e) { 64 65 e.printStackTrace(); 66 } 67 68 } 69 }