通过Java解析xml文档

柔情只为你懂 2022-05-18 03:19 146阅读 0赞

# 一、xml解析方式概叙 #

## 1、解析方法 ##

XML解析方式分为两种：dom和sax

dom：(Document Object Model, 即文档对象模型) 是 W3C 组织推荐的处理 XML 的一种方式。

sax： (Simple API for XML) 不是官方标准，但它是 XML 社区事实上的标准，几乎所有的 XML 解析器都支持它。

## 2、解析器 ##

Crimson、Xerces 、Aelfred2

## 3、解析开发包 ##

Jaxp、Jdom、dom4j

## 4、解析方法比较 ##

### 1.dom方法 ###

优点：使用dom解析xml文档，实现crud特别方便，操作速度也比较快。

缺点：使用dom解析xml文档，如果文件比较大，对内存消耗就特别大，极容易导致内存溢出，所以dom方式不适合操作大的xml文档。

### 2.sax方法 ###

优点：解析速度快、对内存占用少，查找数据特别方便

缺点：只适合查找数据，不适合作增删改操作

# 二、使用jaxp解析 #

## 1、dom方法解析 ##

### 1、方法介绍 ###

javax.xml.parsers 包中的DocumentBuilderFactory用于创建DOM模式的解析器对象 ， DocumentBuilderFactory是一个抽象工厂类，它不能直接实例化，但该类提供了一个newInstance方法 ，这个方法会根据本地平台默认安装的解析器，自动创建一个工厂的对象并返回。

### 2、解析对象 ###

book.xml

<?xml version="1.0" encoding="utf-8" standalone="no"?>
    <书架>
    	<书 name="yyyyyyy">
    		<售价>109</售价>
    		<售价>39元</售价>
    		<书名>Java就业培训教程</书名>
    		<作者>张孝祥</作者>
    		
    		
    	</书>
    	<书>
    		<书名>JavaScript网页开发</书名>
    		<作者>张孝祥</作者>
    		<售价>28.00元</售价>
    	</书>
    
    </书架>

### 3、运用详情 ###

package jaxp;
    
    import java.io.File;
    import java.io.IOException;
    
    import javax.xml.parsers.DocumentBuilder;
    import javax.xml.parsers.DocumentBuilderFactory;
    import javax.xml.parsers.ParserConfigurationException;
    import javax.xml.transform.Transformer;
    import javax.xml.transform.TransformerFactory;
    import javax.xml.transform.dom.DOMSource;
    import javax.xml.transform.stream.StreamResult;
    
    import org.junit.Test;
    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 Demo {
    
    	/**
    	 * 使用jaxp操作xml文档
    	 * @param args
    	 * @throws ParserConfigurationException 
    	 * @throws IOException 
    	 * @throws SAXException 
    	 */
    	public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException {
    		//1.获取工厂
    		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    		
    		
    		//2.产生解析器
    		DocumentBuilder builder = factory.newDocumentBuilder();
    		
    		//3.解析xml文档，得到代表文档的document
    		Document document = builder.parse(new File("src/book.xml"));
    
    		//遍历
    		list(document);
    		
    	}
    	//遍历，得到所有标签
    	public static void list(Node node){
    		
            //判断得到的结点是否为标签
    		if(node.getNodeType()==Node.ELEMENT_NODE){
    			System.out.println(node.getNodeName());
    		}
    		
            //进行遍历
    		NodeList list = node.getChildNodes();
    		for(int i=0;i<list.getLength();i++){
    			Node child = list.item(i);
    			list(child);
    		}
    	}
    	
    	//------------------------对结点进行操作
    	//得到售价结点的值
    	@Test
    	public void read() throws Exception{
    		
    		//1.获取工厂
    		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    		DocumentBuilder builder = factory.newDocumentBuilder();
    		Document document = builder.parse(new File("src/book.xml"));
    		
    		//2.得到第一个售价节点
    		NodeList list = document.getElementsByTagName("售价");
    		Node price = list.item(0);
    		
    		//3.得到该结点的值
    		String value = price.getTextContent();
    		System.out.println(value);
    	}
    	
    	//修改结点的值:<售价>39.00元</售价>改为109
    	@Test
    	public  void update() throws Exception{
    		
    		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    		DocumentBuilder  builder = factory.newDocumentBuilder();
    		Document document = builder.parse(new File("src/book.xml"));
    		
    		Node price = document.getElementsByTagName("售价").item(0);
    		price.setTextContent("109");
    		
    		
    		//把内存中的document写到xml文档
    		TransformerFactory tf = TransformerFactory.newInstance();
    		//得到转换器
    		Transformer ts = tf.newTransformer();
    		ts.transform(new DOMSource(document), new StreamResult(new File("src/book.xml")));
    	}
    	
    	
    	//向指定节点中增加孩子节点（售价节点）
    	@Test
    	public void add() throws Exception{
    		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    		DocumentBuilder  builder = factory.newDocumentBuilder();
    		Document document = builder.parse(new File("src/book.xml"));
    		
    		//创建需要增加的节点
    		Node price = document.createElement("售价");
    		price.setTextContent("59元");
    		
    		//得到需要增加的节点的父亲
    		Node parent = document.getElementsByTagName("书").item(0);
    		
    		//把需要增加的节点挂到父结点上
    		parent.appendChild(price);
    		
    		
    		TransformerFactory tf = TransformerFactory.newInstance();
    		Transformer ts = tf.newTransformer();
    		ts.transform(new DOMSource(document), new StreamResult(new File("src/book.xml")));
    
    	}
    	
    	//向指定位置上插入售价节点
    	@Test
    	public void add2() throws Exception{
    		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    		DocumentBuilder  builder = factory.newDocumentBuilder();
    		Document document = builder.parse(new File("src/book.xml"));
    		
    		//新建要插入的结点
    		Node node = document.createElement("售价");
    		node.setTextContent("39元");
    		
    		Node parent = document.getElementsByTagName("书").item(0);//获取要插入的父节点
    		parent.insertBefore(node, document.getElementsByTagName("书名").item(0));//在该节点的前边插入
    		
    		TransformerFactory tf = TransformerFactory.newInstance();
    		Transformer ts = tf.newTransformer();
    		ts.transform(new DOMSource(document), new StreamResult(new File("src/book.xml")));
    	}
    	
    	//删除xml文档的售价结点
    	@Test
    	public void delete() throws Exception{
    		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    		DocumentBuilder  builder = factory.newDocumentBuilder();
    		Document document = builder.parse(new File("src/book.xml"));
    		
    		Node node = document.getElementsByTagName("售价").item(2);
    		node.getParentNode().removeChild(node);
    		
    		TransformerFactory tf = TransformerFactory.newInstance();
    		Transformer ts = tf.newTransformer();
    		ts.transform(new DOMSource(document), new StreamResult(new File("src/book1.xml")));
    	}
    	
    	//--------------------------该标签属性
    	//操作xml文档属性
    	@Test
    	public void updateAttribute() throws Exception{
    		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    		DocumentBuilder  builder = factory.newDocumentBuilder();
    		Document document = builder.parse(new File("src/book.xml"));
    		
    		
    		//操作xml文档的元素时，一般都把元素当作node对象，但是程序员如果发现node不好使时，就应把node强转成相应类型
    		Node node  = document.getElementsByTagName("书").item(0);
    		Element book = null;
    		if(node.getNodeType()==Node.ELEMENT_NODE){  //在作结点转换之前，最好先判断结点类型
    			book  = (Element)node;
    		}
    		//修改
    		book.setAttribute("name", "yyyyyyy");
    		//增加
    		book.setAttribute("password", "123");
    		//删除
    		book.removeAttribute("password");
    		
    		TransformerFactory tf = TransformerFactory.newInstance();
    		Transformer ts = tf.newTransformer();
    		ts.transform(new DOMSource(document), new StreamResult(new File("src/book.xml")));
    	}
    
    }

### 4、案例解析 ###

**资料**

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
    <exam>
    	<student idcard="111" examid="222">
    		<name>张三</name>
    		<location>沈阳</location>
    		<grade>89</grade>
    	</student>
    	
    	<student idcard="333" examid="444">
    		<name>李四</name>
    		<location>大连</location>
    		<grade>97</grade>
    	</student>
    	
    </exam>

**要求**

1.需求分析

![70][]

2.详细设计

添加用户：

![70 1][]

删除用户：

![70 2][]

查询成绩：

![70 3][]

3.程序实现

javaben：student.java

public class Student {
    
    	 /* <student idcard="111" examid="222">
    		<name>张三</name>
    		<location>沈阳</location>
    		<grade>89</grade>
    	</student>
    	*/
    	private String idcard;
    	private String examid;
    	private String name;
    	private String location;
    	private double grade;
    
    }

工具类：Utils.java

import java.io.File;
    import java.io.IOException;
    
    import javax.xml.parsers.DocumentBuilder;
    import javax.xml.parsers.DocumentBuilderFactory;
    import javax.xml.parsers.ParserConfigurationException;
    import javax.xml.transform.Transformer;
    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.xml.sax.SAXException;
    
    public class XmlUtils {
    	/**
    	 * 工具类中的方法一般都是静态方法
    	 * @return
    	 * @throws ParserConfigurationException
    	 * @throws SAXException
    	 * @throws IOException
    	 */
    
    	//得到document
    	public static Document getDocument() throws ParserConfigurationException, SAXException, IOException{
    		
    		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    		DocumentBuilder builder = factory.newDocumentBuilder();
    		return builder.parse(new File("src/exam.xml"));
    	}
    	
    	//将结果写入到xml文件
    	public static void write2Xml(Document document) throws TransformerException{
    		
    		TransformerFactory factory = TransformerFactory.newInstance();
    		Transformer tf = factory.newTransformer();
    		tf.transform(new DOMSource(document), new StreamResult(new File("src/exam.xml")));
    		
    	}
    }

持久化操作：StudentsDao.java

import java.io.IOException;
    
    import javax.management.RuntimeErrorException;
    import javax.xml.parsers.ParserConfigurationException;
    
    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;
    
    import com.shen.mode.Student;
    import com.shen.utils.XmlUtils;
    
    public class StudentsDao {
    
    	/*
    	 <student idcard="111" examid="222">
    		<name>张三</name>
    		<location>沈阳</location>
    		<grade>89</grade>
    	</student>
    
    	 */
    	public void add(Student student){
    		try{
    			Document document = XmlUtils.getDocument();
    			//student_node  //ctrl+1  rename in file
    			Element student_node = document.createElement("student");
    			student_node.setAttribute("examid", student.getExamid());
    			student_node.setAttribute("idcard", student.getIdcard());
    			
    			Element name = document.createElement("name");
    			name.setTextContent(student.getName());
    			
    			Element location = document.createElement("location");
    			location.setTextContent(student.getLocation());
    			
    			Element grade = document.createElement("grade");
    			grade.setTextContent(student.getGrade()+"");
    			
    			student_node.appendChild(name);
    			student_node.appendChild(location);
    			student_node.appendChild(grade);
    			
    			//得到exam结点，并把student挂上去
    			document.getElementsByTagName("exam").item(0).appendChild(student_node);
    			
    			XmlUtils.write2Xml(document);
    		}catch (Exception e) {
    			throw new RuntimeException(e);
    		}
    	}
    	
    	public void delete(String name){
    		try {
    			Document document=XmlUtils.getDocument();
    			NodeList list=document.getElementsByTagName("name");
    			for(int i=0;i<list.getLength();i++)
    			{
    				Node node=list.item(i);
    				
    				if(node.getTextContent().equals(name)){
    					node.getParentNode().getParentNode().removeChild(node.getParentNode());
    					XmlUtils.write2Xml(document);
    					return;
    				}
    			}
    			throw new RuntimeException("对不起，你要删除的学生不存在");//异常也是一个返回值
    		} catch (Exception e) {
    			throw new RuntimeException(e);
    		}
    	}
    	
    	
    	public Student find(String examid){
    		
    		try{
    		Document document=XmlUtils.getDocument();
    		
    		NodeList list=document.getElementsByTagName("student");
    		for (int i = 0; i < list.getLength(); i++) {
    			Element student=(Element)list.item(i);
    			String s_examid=student.getAttribute(examid);
    			if(s_examid.equals(examid))
    			{
    				//找到
    				Student s=new Student();
    				s.setExamid(student.getAttribute("examid"));
    				s.setExamid(student.getAttribute("idcard"));
    				
    				s.setName(student.getElementsByTagName("name").item(0).getTextContent());
    				s.setLocation(student.getElementsByTagName("location").item(0).getTextContent());
    				s.setGrade(Double.parseDouble(student.getElementsByTagName("garde").item(0).getTextContent()));
    			    return s;
    			    		
    			}
    		}
    		
    		return null;
    		}catch(Exception e){}
    		return null;
    	}
    }

主方法：Main.java

import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStreamReader;
    
    import com.shen.dao.StudentsDao;
    import com.shen.mode.Student;
    
    public class Main {
    
    	public static void main(String[] args) throws IOException {
    
    		System.out.println("添加学生 (a)  查找学生(b)  删除学生(c)");
    		System.out.print("请输入操作类型：");
    
    		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    		String type = br.readLine();
    
    		if (type.equalsIgnoreCase("a")) {
    			// 添加学生
    
    			try {
    				System.out.print("请输入学生姓名：");
    				String name = br.readLine();
    
    				System.out.print("请输入学生准考证号：");
    				String examid = br.readLine();
    
    				System.out.print("请输入学生身份证号：");
    				String idcard = br.readLine();
    
    				System.out.print("请输入学生所在地：");
    				String location = br.readLine();
    
    				System.out.print("请输入学生成绩：");
    				String grade = br.readLine();
    
    				Student student = new Student();
    				student.setExamid(examid);
    				student.setGrade(Double.parseDouble(grade));
    				student.setIdcard(idcard);
    				student.setLocation(location);
    				student.setName(name);
    
    				StudentsDao dao = new StudentsDao();
    				dao.add(student);
    				System.out.println("恭喜，录入成功！！！");
    			} catch (Exception e) {
    				System.out.println("对不起，录入失败！！");
    			}
    
    		} else if (type.equalsIgnoreCase("b")) {
    			// 查找学生
    			System.out.println("请输入学生的准考证号：");
    			String examid=br.readLine();
    			
    			StudentsDao dao=new StudentsDao();
    			Student student=dao.find(examid);
    			if(student==null){
    				System.out.println("对不起，你要查找的学生不存在！！！");
    			}else{
    				System.out.println("你要查找的学生信息如下：");
    				System.out.println("姓名："+student.getName());
    				System.out.println("身份证："+student.getIdcard());
    				System.out.println("准考证："+student.getExamid());
    				System.out.println("所在地："+student.getLocation());
    				System.out.println("成绩"+student.getGrade());
    			}
    		} else if (type.equalsIgnoreCase("c")) {
    			// 删除学生
    			try{
    			System.out.println("请输入要删除学生的姓名：");
    			String name=br.readLine();
    			
    			StudentsDao dao=new StudentsDao();
    			dao.delete(name);
    			System.out.println("删除成功");
    			}catch(Exception e){System.out.println("删除失败");}
    		} else {
    			System.out.println("不支持此类操作！！！");
    		}
    
    	}
    }

## 2、sax方法解析 ##

### 1、方法介绍 ###

在使用 DOM 解析 XML 文档时，需要读取整个 XML 文档，在内存中构架代表整个 DOM 树的Doucment对象，从而再对XML文档进行操作。此种情况下，如果 XML 文档特别大，就会消耗计算机的大量内存，并且容易导致内存溢出。SAX解析允许在读取文档的时候，即对文档进行处理，而不必等到整个文档装载完才会文档进行操作。

### 2、解析对象 ###

book.xml

### 3、运用详情 ###

import java.io.IOException;
    
    import javax.xml.parsers.ParserConfigurationException;
    import javax.xml.parsers.SAXParser;
    import javax.xml.parsers.SAXParserFactory;
    
    import org.xml.sax.Attributes;
    import org.xml.sax.ContentHandler;
    import org.xml.sax.Locator;
    import org.xml.sax.SAXException;
    import org.xml.sax.XMLReader;
    import org.xml.sax.helpers.DefaultHandler;
    
    public class Demo1 {
    
    	/**
    	 *sax方式解析book1.xml文件
    	 * @throws SAXException 
    	 * @throws ParserConfigurationException 
    	 * @throws IOException 
    	 */
    	public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException {
    		
    
    		//1.创建工厂
    		SAXParserFactory factory = SAXParserFactory.newInstance();
    		
    		//2.用工厂创建解析器
    		SAXParser sp = factory.newSAXParser();
    		
    		//3.利用解析器得到reader
    		XMLReader reader = sp.getXMLReader();
    		
    		//4、在解析xml文档之前，设置好事件处理器
    		reader.setContentHandler(new MyContentHandler2());
    		
    		//4.利用reader读取 xml文档
    		reader.parse("src/book1.xml");
    	}
    }
    //用于获取第一个售价节点的值：<售价>109</售价>
    class MyContentHandler2 extends DefaultHandler{
    
    	private boolean isOk = false;
    	private int index = 1;
    	@Override
    	public void characters(char[] ch, int start, int length)
    			throws SAXException {
    		if(isOk==true && index==1){
    			System.out.println(new String(ch,start,length));
    		}
    	}
    
    	@Override
    	public void startElement(String uri, String localName, String name,
    			Attributes attributes) throws SAXException {
    		if(name.equals("售价")){
    			isOk = true;
    		}
    	}
    
    	@Override
    	public void endElement(String uri, String localName, String name)
    			throws SAXException {
    		if(name.equals("售价")){
    			isOk = false;
    			index++;
    		}
    	}
    	
    	
    	
    	
    	
    }
    
    //得到xml文档内容的事件处理器
    class MyContentHandler implements ContentHandler{
            //开始标签（Attributes表示属性）
    	public void startElement(String uri, String localName, String name,
    			Attributes atts) throws SAXException {
    		
    		System.out.println("当前解析到了:" + name + ",这个标签是开始标签");
    		for(int i=0;i<atts.getLength();i++){
    			String attname = atts.getQName(i);
    			String attvalue = atts.getValue(i);
    			
                            //打印出各个属性
    			System.out.println(attname + "=" + attvalue);
    		}
    		
    		
    	}
    	
    	public void endElement(String uri, String localName, String name)
    	throws SAXException {
    		
    		System.out.println("当前解析到了:" + name + ",这个标签是结束标签");
    	
    	}
    	
    	public void characters(char[] ch, int start, int length)
    			throws SAXException {
    		
    		System.out.println("当前解析到了内容：" + new String(ch,start,length));
    	}
    
    	public void endDocument() throws SAXException {
    		// TODO Auto-generated method stub
    		
    	}
    
    
    
    	public void endPrefixMapping(String prefix) throws SAXException {
    		// TODO Auto-generated method stub
    		
    	}
    
    	public void ignorableWhitespace(char[] ch, int start, int length)
    			throws SAXException {
    		// TODO Auto-generated method stub
    		
    	}
    
    	public void processingInstruction(String target, String data)
    			throws SAXException {
    		// TODO Auto-generated method stub
    		
    	}
    
    	public void setDocumentLocator(Locator locator) {
    		// TODO Auto-generated method stub
    		
    	}
    
    	public void skippedEntity(String name) throws SAXException {
    		// TODO Auto-generated method stub
    		
    	}
    
    	public void startDocument() throws SAXException {
    		// TODO Auto-generated method stub
    		
    	}
    
    	
    
    	public void startPrefixMapping(String prefix, String uri)
    			throws SAXException {
    		// TODO Auto-generated method stub
    		
    	}
    
    
    	
    }

# 三、使用dom4j解析 #

注意：使用dom4j解析需要自己引入jar包，引入该包可能不够

## 1、解析对象 ##

book.xml

## 2、实现代码 ##

public class Main {
    
    	//读取xml文档数据：<书名>Java就业培训教程</书名>
    	@Test
    	public void read() throws Exception{
    		
    		SAXReader reader = new SAXReader();
    		Document document = reader.read(new File("src/book.xml"));
    		
    		Element root = document.getRootElement();
    		Element bookname = root.element("书").element("书名");
    		System.out.println(bookname.getText());
    	}
    	
    	//<书 name="yyyyyyy">
    	@Test
    	public void readAttr() throws Exception{
    		
    		SAXReader reader = new SAXReader();
    		Document document = reader.read(new File("src/book.xml"));
    		
    		Element root = document.getRootElement();
    		String value = root.element("书").attributeValue("name");
    		System.out.println(value);
    	}
    	
    	//向xml文档中添加<售价>19元</售价>
    	@Test
    	public void add() throws Exception{
    		SAXReader reader = new SAXReader();
    		Document document = reader.read(new File("src/book.xml"));
    		
    		Element price = DocumentHelper.createElement("售价");
    		price.setText("19元");
    		
    		document.getRootElement().element("书").add(price);
    		
    		OutputFormat format = OutputFormat.createPrettyPrint();
    		format.setEncoding("UTF-8");
    		
    		XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),format);
    		writer.write(document);  //utf-8
    		writer.close();
    	}
    	
    	//修改：<售价>109</售价>  为209
    	@Test
    	public void update() throws Exception{
    		SAXReader reader = new SAXReader();
    		Document document = reader.read(new File("src/book1.xml"));
    		
    		Element price = (Element) document.getRootElement().element("书").elements("售价").get(1);
    		price.setText("209元");
    		
    		OutputFormat format = OutputFormat.createPrettyPrint();
    		format.setEncoding("UTF-8");
    		
    		XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),format);
    		writer.write(document);  //utf-8
    		writer.close();
    		
    	}
    	//删除：<售价>109</售价>
    	@Test
    	public void delete() throws Exception{
    		SAXReader reader = new SAXReader();
    		Document document = reader.read(new File("src/book.xml"));
    		
    		Element price = (Element) document.getRootElement().element("书").elements("售价").get(0);
    		price.getParent().remove(price);
    		
    		OutputFormat format = OutputFormat.createPrettyPrint();
    		format.setEncoding("UTF-8");
    		
    		XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),format);
    		writer.write(document);  //utf-8
    		writer.close();
    	}
    
    	
    	//向指定位置增加售价结点
    	@Test
    	public void add2() throws Exception{
    		SAXReader reader = new SAXReader();
    		Document document = reader.read(new File("src/book.xml"));
    		
    		Element price = DocumentHelper.createElement("售价");
    		price.setText("19元");
    		
    		List list = document.getRootElement().element("书").elements();
    		list.add(1, price);
    		
    		//格式化输出（保持原来的样式）
    		OutputFormat format = OutputFormat.createPrettyPrint();
    		format.setEncoding("UTF-8");
    		
    		XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),format);
    		writer.write(document);  //utf-8
    		writer.close();
    		
    	}
    
    }

## 3、使用xpath技术实现查找 ##

### 1.代码示例 ###

import java.io.File;
    
    import org.dom4j.Document;
    import org.dom4j.Element;
    import org.dom4j.io.SAXReader;
    import org.junit.Test;
    
    public class Mais {
    
    	@Test
    	public void findWithXpath() throws Exception{
    		SAXReader reader = new SAXReader();
    		Document document = reader.read(new File("src/book.xml"));
    		
    		Element e = (Element) document.selectNodes("//书名").get(1);
    		System.out.println(e.getText());
    	}
    }

### 2.运用举例 ###

通过匹配用户信息进行登陆

users.xml

<?xml version="1.0" encoding="UTF-8"?>
    <users>
    	
    	
    	<user username="aaa" password="123"/>
    	
    	<user username="bbb" password="123"/>
    	
    	<user username="ccc" password="123"/>
    
    </users>

@Test
    	public void findUser() throws Exception{
    		String username = "aaa";
    		String password = "1233";
    		
    		SAXReader reader = new SAXReader();
    		Document document = reader.read(new File("src/users.xml"));
    		//single单一的
    		Element e = (Element) document.selectSingleNode("//user[@username='"+username+"' and @password='"+password+"']");
    		if(e!=null){
    			System.out.println("让用户登陆成功！！");
    		}else{
    			System.out.println("用户名和密码不正确！！");
    		}
    	
    	}

[70]: /images/20220518/d77630796fab42dc96966937f3e0b16e.png
[70 1]: /images/20220518/0e3cfc68280f47cd9939a88c0f828f1d.png
[70 2]: /images/20220518/1eb1ca200c8646adbf36ee84921870ff.png
[70 3]: /images/20220518/570284540dff466c89c18dbdedb069f8.png

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