Java解析XML的四种方法

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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。

项目结构图：
这里写图片描述

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>

首先定义一个操作XML文档的接口XmlInterface，它定义了XML文档的建立与解析的接口。

XmlInterface.java

package xml;/** * @description XML文档建立与解析的接口  */public interface XmlInterface {       /**     * @description 建立XML文档      * @param fileName 文件全路径名称      */     public void createXml(String fileName);      /**     * @description      * @param fileName 解析XML文档      */    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 xml;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;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;public class Dom implements XmlInterface{    private Document document;     public void init(){        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();        DocumentBuilder builder;        try {            builder = factory.newDocumentBuilder();            this.document = builder.newDocument();        } catch (ParserConfigurationException e) {             e.printStackTrace();        }    }    @Override    public void createXml(String fileName) {        Element root = this.document.createElement("employees");         Element employee = this.document.createElement("employee");        Element name = this.document.createElement("name");        Element sex = this.document.createElement("sex");        Element age = this.document.createElement("age");        this.document.appendChild(root);        name.appendChild(this.document.createTextNode("sunshine"));        sex.appendChild(this.document.createTextNode("M"));        age.appendChild(this.document.createTextNode("20"));        employee.appendChild(name);        employee.appendChild(sex);        employee.appendChild(age);        root.appendChild(employee);        TransformerFactory trf = TransformerFactory.newInstance();               try {            Transformer tr = trf.newTransformer();            DOMSource source = new DOMSource(document);            tr.setOutputProperty(OutputKeys.ENCODING, "utf8");            tr.setOutputProperty(OutputKeys.INDENT, "yes");            PrintWriter pw = new PrintWriter(new FileOutputStream(fileName));            StreamResult result = new StreamResult(pw);            tr.transform(source, result);            System.out.println("生成xml文件成功！");        }         catch (TransformerConfigurationException e) {            e.printStackTrace();        }         catch (FileNotFoundException e) {             e.printStackTrace();        }         catch (TransformerException e) {             e.printStackTrace();        }        }    @Override    public void parserXml(String fileName) {        try {             DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();             DocumentBuilder db = dbf.newDocumentBuilder();             Document document = db.parse(fileName);             //找到employees结点            Element employees = document.getDocumentElement();             //找到employee集            NodeList employeeList = employees.getChildNodes();             for (int i = 0; i < employeeList.getLength(); i++) {                     Node node = employeeList.item(i);                     //细分到属性 比如name                    NodeList employeeMeta = node.getChildNodes();                      for (int j = 0; j < employeeMeta.getLength(); j++) {                           if(! "#text".equals(employeeMeta.item(j).getNodeName())){                            System.out.println(employeeMeta.item(j).getNodeName() + ":" + employeeMeta.item(j).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());         }     }    public static void main(String[] args) {        Dom dom =  new Dom();        dom.init();        dom.createXml("dom.xml");           dom.parserXml("dom.xml");    }}

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 xml;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;public class Sax implements XmlInterface{    @Override    public void createXml(String fileName) {        System.out.println("<<"+fileName+">>");             }    @Override    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();         }     }       public static void main(String[] args) {        Sax sax = new Sax();        sax.createXml("sax.xml");        sax.parserXml("sax.xml");    }}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 {        StringBuffer buffer = new StringBuffer();          for(int i = start ; i < start+length ; i++){              switch(ch[i]){                  case '\\':buffer.append("\\\\");break;                  case '\r':buffer.append("\\r");break;                  case '\n':buffer.append("\\n");break;                  case '\t':buffer.append("\\t");break;                  case '\"':buffer.append("\\\"");break;                  default : buffer.append(ch[i]);               }          }          System.out.println(buffer);    }   }

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。

package xml;   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; public class Dom4j implements XmlInterface {    @Override    public void createXml(String fileName) {        Document document = DocumentHelper.createDocument();           Element employees = document.addElement("employees");           Element employee = employees.addElement("employee");           Element name = employee.addElement("name");           Element sex = employee.addElement("sex");           Element age = employee.addElement("age");                   name.setText("sunshine");                   sex.setText("M");                   age.setText("20");           try {               Writer fileWriter=new FileWriter(fileName);               XMLWriter xmlWriter=new XMLWriter(fileWriter);               xmlWriter.write(document);               xmlWriter.close();           } catch (IOException e) {                        System.out.println(e.getMessage());           }           }    @Override    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());           }       }      public static void main(String[] args) {        Dom4j dom4j = new Dom4j();        dom4j.createXml("dom4j.xml");        dom4j.parserXml("dom4j.xml");    }}

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。

package xml;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;public class JDom implements XmlInterface {    @Override    public void createXml(String fileName) {        Document document;        Element root = new Element("employees");        Element employee = new Element("employee");        Element name = new Element("name");        name.setText("sunshine");        Element sex = new Element("sex");        sex.setText("M");        Element age = new Element("age");        age.setText("23");        document = new Document(root);        root.addContent(employee);        employee.addContent(name);        employee.addContent(sex);        employee.addContent(age);        XMLOutputter XMLOut = new XMLOutputter();        try {            XMLOut.output(document, new FileOutputStream(fileName));        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }    @Override    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();        }    }    public static void main(String[] args) {        JDom jdom = new JDom();        jdom.createXml("jdom.xml");        jdom.parserXml("jdom.xml");    }}

创建的文件都用的相对路径，要去工作目录文件夹里找，eclipse没有显示出来。

项目工程下载

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