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,平台的无关性使得很多场合都需要用到XML。本文将详细介绍用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"?> 
<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）。 

package com.xmlTest;

import java.io.File;
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;

/**
 * ClassName: XmlTest date: 2015年2月28日 上午10:57:42
 *
 * @author limh
 * @since JDK 1.7 DOM生成与解析XML文档
 */
public class XmlDomDemoTest implements XmlDocument {
    private Document document;

    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 fileName1) {
       String fileName = fileName1;
       //创建File对象，参数为String类型，表示目录名
       File myFile = new File(fileName);
       //判断文件是否存在，如果不存在则调用createNewFile()方法创建新目录，否则跳至异常处理代码
       if(!myFile.exists())
        try {
            myFile.createNewFile();
        } catch (IOException e1) {
            e1.printStackTrace();
        }
        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, "utf-8");
            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());
        }
    }
    public static void main(String[] args) {
        String pathname = "/home/zhangmeng/桌面/232323/ccc.xml";
        XmlDomDemoTest xmldomdemotest =     new XmlDomDemoTest();
        xmldomdemotest.init();
        //xmldomdemotest.createXml(pathname);//创建xml
        xmldomdemotest.parserXml(pathname);//解析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；

Java代码

package com.xmlTest;

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 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。

Java代码

package com.xmlTest;

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);
           //判断文件是否存在，如果不存在则调用createNewFile()方法创建新目录，否则跳至异常处理代码
           if(!inputXml.exists())
            try {
                inputXml.createNewFile();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
        
        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");
    }
        public static void main(String[] args) {
        String pathname = "/home/zhangmeng/桌面/232323/a22222.xml";
        Dom4jDemo xmldomdemotest =     new Dom4jDemo();
        //xmldomdemotest.createXml(pathname);//创建xml
        xmldomdemotest.parserXml(pathname);//解析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 com.xmlTest;

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; 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();
        }

    }
}