详解Java解析XML的四种方法

2019-11-26 13:35:11

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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。

/** * * @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）。

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；

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));    }    }  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));  }  }

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。

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 {    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

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。

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("employee");   for(int i=0;iElement employee=(Element)employeeList.get(i);   List employeeInfo=employee.getChildren();   for(int j=0;jSystem.out.println(((Element)employeeInfo.get(j)).getName()+":"+((Element)employeeInfo.get(j)).getValue());    }   }   } catch (JDOMException e) {    e.printStackTrace();   } catch (IOException e) {    e.printStackTrace();   }    }   }

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