XML可扩展标记语言的解析

xml提供一套跨平台， 跨网络，跨程序的数据描述语言，使用xml可以方便的实现数据交换，系统配置，内容管理等常见功能。

基本格式

studeng，name，sex，age为元素节点

id="001"为属性节点

张三 为文本节点

<?xml version="1.0" encoding="UTF-8"?>
<student>
	<name id="001">张三</name>
	<sex>男</sex>
	<age>20</age>
</student>

DOM方式解析XML

把整个XML文档加载到内存，转化为DOM树，应用程序可以随机访问DOM树的任何数据

优点灵活性强，速度快

缺点 消耗资源比较多

文档构建工厂

factory单例方式获取实例

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newDocumentBuilder 文档构建模型

parse解析配置获取xml文档

getElementsByTagName通过标签名字获取dom节点

nodeList.item(0)获取第一个<student>...</student>元素

getFirstChild 获取第一个子节点 张三 getNodeValue获取值

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;


	public static void main(String[] args) {
		DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
		try {
			DocumentBuilder builder=factory.newDocumentBuilder();
			Document doc=builder.parse("src/student.xml");
			NodeList nodeList=doc.getElementsByTagName("student");
			Element e=(Element)nodeList.item(0);
			System.out.println("姓名："+e.getElementsByTagName("name").item(0).getFirstChild().getNodeValue());
			System.out.println("性别："+e.getElementsByTagName("sex").item(0).getFirstChild().getNodeValue());
			System.out.println("年龄："+e.getElementsByTagName("age").item(0).getFirstChild().getNodeValue());
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

解析属性

<?xml version="1.0" encoding="UTF-8"?>
<students>
	<student id="001">
		<name>张三</name>
		<sex>男</sex>
		<age>20</age>
	</student>
	<student id="002">
		<name>李四</name>
		<sex>女</sex>
		<age>21</age>
	</student>
</students>

getAttributes 获取node节点的所有属性

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

	public static void printNodeAttr(Node node){
		NamedNodeMap namedNodeMap=node.getAttributes();
		for(int i=0;i<namedNodeMap.getLength();i++){
			Node attrNode=namedNodeMap.item(i);
			System.out.println(attrNode.getNodeName()+":"+attrNode.getFirstChild().getNodeValue());
		}
	}
	
	public static void main(String[] args) {
		DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
		try {
			DocumentBuilder builder=factory.newDocumentBuilder();
			Document doc=builder.parse("src/students.xml");
			NodeList nodeList=doc.getElementsByTagName("students");
			Element element=(Element)nodeList.item(0);
			NodeList studentsNodeList=element.getElementsByTagName("student");
			for(int i=0;i<studentsNodeList.getLength();i++){
				Element e=(Element)studentsNodeList.item(i);
				System.out.println("姓名："+e.getElementsByTagName("name").item(0).getFirstChild().getNodeValue());
				printNodeAttr(e.getElementsByTagName("name").item(0));
				System.out.println("性别："+e.getElementsByTagName("sex").item(0).getFirstChild().getNodeValue());
				System.out.println("年龄："+e.getElementsByTagName("age").item(0).getFirstChild().getNodeValue());
				System.out.println("================");
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

SAX方式解析XML

SAX对文档进行顺序扫描，扫描文档的开始与结束，元素的开始于结束，通知事件处理函数，由事件处理函数做相应的动作。

优点 消耗资源少，适合大文件解析

缺点 只能读取不能修改，开发复杂

定义事件

startDocument 文档开始时候的事件

startElement 元素开始事件 元素是节点的一个子集

endElement 元素扫描完事件

characters 文本节点事件

SAXParserFactory 获取工厂，解析工厂

newSAXParser 获取解析器

qName 所有元素  attributes所有属性 attributes.getQName(i)属性的名字

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 extends DefaultHandler{

	@Override
	public void startDocument() throws SAXException {
		System.out.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
	}

	@Override
	public void endDocument() throws SAXException {
		System.out.print("\n 扫描文档结束");
	}

	@Override
	public void startElement(String uri, String localName, String qName,
			Attributes attributes) throws SAXException {
		System.out.print("<");
		System.out.print(qName);
		if(attributes!=null){
			for(int i=0;i<attributes.getLength();i++){
				System.out.print(" "+attributes.getQName(i)+"=\""+attributes.getValue(i)+"\"");
			}
		}
		System.out.print(">");
	}

	@Override
	public void endElement(String uri, String localName, String qName)
			throws SAXException {
		System.out.print("</");
		System.out.print(qName);
		System.out.print(">");
	}

	@Override
	public void characters(char[] ch, int start, int length)
			throws SAXException {
		System.out.print(new String(ch,start,length));
	}

	public static void main(String[] args) throws Exception{
		SAXParserFactory factory=SAXParserFactory.newInstance();
		SAXParser parser=factory.newSAXParser();
		parser.parse("src/student.xml", new SAX());
	}
}

<?xml version="1.0" encoding="UTF-8"?>
<students>
	<student id="001">
		<name>张三</name>
		<sex>男</sex>
		<age>20</age>
	</student>
	<student id="002">
		<name>李四</name>
		<sex>女</sex>
		<age>21</age>
	</student>
</students>

import java.util.ArrayList;
import java.util.List;

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;

import com.java1234.model.Student;

public class SAX extends DefaultHandler{
	private List<Student> students=null;
	private Student student=null;
	private String preTag=null; // 标记上一个节点名称
	
	@Override
	public void startDocument() throws SAXException {
		System.out.println("开始读取学生信息");
		students=new ArrayList<Student>();
	}

	@Override
	public void endDocument() throws SAXException {
		System.out.println("\n 学生信息读取完毕");
	}

	@Override
	public void startElement(String uri, String localName, String qName,
			Attributes attributes) throws SAXException {
		if("student".equals(qName)){
			student=new Student();
			student.setId(attributes.getValue(0));//获取对象放到集合中
		}
		preTag=qName;
	}

	@Override
	public void endElement(String uri, String localName, String qName)
			throws SAXException {
		if("student".equals(qName)){
			students.add(student);
			student=null;
		}
		preTag=null;
	}

	@Override
	public void characters(char[] ch, int start, int length)
			throws SAXException {
		if(preTag!=null){
			String content=new String(ch,start,length);
			if("name".equals(preTag)){
				student.setName(content);
			}else if("sex".equals(preTag)){
				student.setSex(content);
			}else if("age".equals(preTag)){
				student.setAge(Integer.parseInt(content));
			}
		}
	}

	public static void main(String[] args) throws Exception{
		SAXParserFactory factory=SAXParserFactory.newInstance();
		SAXParser parser=factory.newSAXParser();
		SAX sax=new SAX();
		parser.parse("src/students.xml", sax);
		for(Student s:sax.students){
			System.out.println(s);
		}
	}
}

JDOM和DOM4j解析XML

JDOM生成XML

<?xml version="1.0" encoding="UTF-8"?>
<student id="001" aa="xx">
	<name>张三</name>
	<sex>男</sex>
	<age>20</age>
</student>

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import org.jdom2.Attribute;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.output.XMLOutputter;

public class JDOM {

	public static void main(String[] args) {
		Element student=new Element("student");
		
		Attribute id=new Attribute("id", "001");
		Attribute aa=new Attribute("aa", "xx");
		student.setAttribute(id);
		student.setAttribute(aa);
		
		Element name=new Element("name");
		name.setText("张三");
		student.addContent(name);
		
		Element sex=new Element("sex");
		sex.setText("男");
		student.addContent(sex);
		
		Element age=new Element("age");
		age.setText("20");
		student.addContent(age);
		
		Document document=new Document(student);//根节点
		XMLOutputter out=new XMLOutputter();//xml输出器
		out.setFormat(out.getFormat().setEncoding("UTF-8"));
		
		try {
			out.output(document, new FileOutputStream("src/student2.xml"));
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

JDOM遍历XML

<?xml version="1.0" encoding="UTF-8"?>
<students>
	<student id="001">
		<name>张三</name>
		<sex>男</sex>
		<age>20</age>
	</student>
	<student id="002">
		<name>李四</name>
		<sex>女</sex>
		<age>21</age>
	</student>
</students>

SAXBuilder()构建文本

import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.input.SAXBuilder;

public class JDOM {

	public static void main(String[] args) throws Exception{
		SAXBuilder builder=new SAXBuilder();
		Document document=builder.build("src/students.xml");
		Element students=document.getRootElement();
		List studentList=students.getChildren("student");
		for(int i=0;i<studentList.size();i++){
			Element student=(Element)studentList.get(i);
			String id=student.getAttributeValue("id");
			String name=student.getChildText("name");
			String sex=student.getChildText("sex");
			String age=student.getChildText("age");
			System.out.println("学号："+id+";姓名："+name+";性别："+sex+";年龄："+age);
		}
	}
}

DOM4J生成XML

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.XMLWriter;

public class DOM4J {

	public static void main(String[] args) {
		Document document=DocumentHelper.createDocument();
		Element studentElement=document.addElement("student");
		studentElement.addAttribute("id", "001");
		studentElement.addAttribute("aa", "xx");
		
		Element name=studentElement.addElement("name");
		name.setText("张三");
		Element sex=studentElement.addElement("sex");
		sex.setText("男");
		Element age=studentElement.addElement("age");
		age.setText("20");
		
		OutputFormat format=OutputFormat.createPrettyPrint();
		format.setEncoding("UTF-8");
		try {
			XMLWriter writer=new XMLWriter(new FileOutputStream("src/student3.xml"),format);
			writer.write(document);
			writer.close();
		} catch (UnsupportedEncodingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

DOM4J解析XML

import java.util.Iterator;

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

public class DOM4J {

	public static void main(String[] args) throws Exception{
		SAXReader saxReader=new SAXReader();
		Document document=saxReader.read("src/students.xml");
		Element rootElement=document.getRootElement();
		Iterator iter=rootElement.elementIterator();
		while(iter.hasNext()){
			Element studentElement=(Element)iter.next();
			System.out.println("学号："+studentElement.attributeValue("id"));
			System.out.println("姓名："+studentElement.elementText("name"));
			System.out.println("性别："+studentElement.elementText("sex"));
			System.out.println("年龄："+studentElement.elementText("age"));
			System.out.println("=========");
		}
	}
}