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XML解析 ​

XML解析 ​

定义：Extension Markup Language ，可扩展标记语言，简称XML。

#####特点

1.XML与操作系统无关。

2.实现不同系统之间的数据交换。

3.XML文件由一系列的标签元素组成。

#####基本语法

<标签名 属性名="属性值" 属性名="属性值">元素内容</标签名>

注意事项 ​

1.属性值用双引号包裹。

2.一个标签可以有多个属性。

3.属性值中不能包含特殊字符<,>,",',&。

4.XML标签区分大小写。

5.XML必须有正确的嵌套结构。

6.同级标签以缩进对齐。

7.标签名称可以包含字母，数组或者其他的字符。

8.标签名称不能以数字或者标点符号开始。

9.标签名称不能包含空格。

xml
<			&lt;
>			&gt;
"			&quot;
'			&apos;
&			&amp;
XML案例 ​
xml
<?xml version="1.0" encoding="UTF-8"?>
<books>
    <book id="1">
        <name>Java高级编程</name>
        <author>张三</author>
        <price>33.5</price>
    </book>
    <book id="2">
        <name>数据结构</name>
        <author>李四</author>
        <price>43.5</price>
    </book>
</books>

实际开发中，我们的重点是读取XML文件，而非定义XML的结构，只要你的程序可以读取XML文件包含的数据即可，XML没有特殊的要求。

dom4j是一款优秀的Java XML API（ApplicationInterface），性能优异，功能强大，使用简单。

使用前需引入第三方dom4j架包，并add to build path。

java
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.util.Iterator;

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

public class Test {
	public static void main(String[] args) {
		delete();
	}
	/*
	 * 读取xml
	 */
	public static void read() {
		try {
			//1.实例化SAXReader对象
			SAXReader saxReader = new SAXReader();
			//2.读取xml文件，生成Document
			Document document = saxReader.read("src/book.xml");
			//3.获取根节点元素
			Element root = document.getRootElement();
			//4.迭代根节点
			Iterator<Element> rootIter = root.elementIterator();
			while(rootIter.hasNext()) {
				Element element = rootIter.next();
				String id = element.attributeValue("id");
				System.out.println("id:"+id);
				//5.继续迭代
				Iterator<Element> elementIter = element.elementIterator();
				while(elementIter.hasNext()) {
					Element attribute = elementIter.next();
					String name = attribute.getName();
					String value = attribute.getText();
					System.out.println(name+":"+value);
				}
			}
		} catch (DocumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	/*
	 * 添加节点
	 */
	public static void add() {
		try {
			//1.实例化SAXReader对象
			SAXReader saxReader = new SAXReader();
			//2.读取xml文件，生成Document
			Document document = saxReader.read("src/book.xml");
			//3.获取根节点元素
			Element root = document.getRootElement();
			//4.给根节点添加book节点
			Element book = root.addElement("book");
			//5.给book添加id属性
			book.addAttribute("id", "3");
			//6.给book添加name节点
			Element name = book.addElement("name");
			name.addText("MySQL数据库");
			book.addElement("author").addText("王五");
			book.addElement("price").addText("60.5");
			//7.将修改之后的document对象写入book.xml
			OutputStream outputStream = new FileOutputStream("src/book.xml");
			XMLWriter xmlWriter = new XMLWriter(outputStream);
			xmlWriter.write(document);
			xmlWriter.close();
			outputStream.close();
		} catch (DocumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (UnsupportedEncodingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	/*
	 * 修改xml
	 */
	public static void update() {
		try {
			//1.实例化SAXReader对象
			SAXReader saxReader = new SAXReader();
			//2.读取xml文件，生成Document
			Document document = saxReader.read("src/book.xml");
			//3.获取根节点元素
			Element root = document.getRootElement();
			//4.迭代根节点
			Iterator<Element> rootIter = root.elementIterator();
			while(rootIter.hasNext()) {
				Element element = rootIter.next();
				element.addAttribute("type", "计算机");
			}
			//5.将修改之后的document对象写入book.xml
			OutputStream outputStream = new FileOutputStream("src/book.xml");
			XMLWriter xmlWriter = new XMLWriter(outputStream);
			xmlWriter.write(document);
			xmlWriter.close();
			outputStream.close();
		} catch (DocumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (UnsupportedEncodingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	/*
	 * 删除节点
	 */
	public static void delete() {
		try {
			//1.实例化SAXReader对象
			SAXReader saxReader = new SAXReader();
			//2.读取xml文件，生成Document
			Document document = saxReader.read("src/book.xml");
			//3.获取根节点元素
			Element root = document.getRootElement();
			//4.迭代根节点
			Iterator<Element> rootIter = root.elementIterator();
			while(rootIter.hasNext()) {
				Element element = rootIter.next();
				String id = element.attributeValue("id");
				if(id.equals("2")) {
					element.getParent().remove(element);
				}
			}
			//5.将修改之后的document对象写入book.xml
			OutputStream outputStream = new FileOutputStream("src/book.xml");
			XMLWriter xmlWriter = new XMLWriter(outputStream);
			xmlWriter.write(document);
			xmlWriter.close();
			outputStream.close();
		} catch (DocumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (UnsupportedEncodingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

XML解析+反射的应用 ​

根据xml文件创建类和对象

xml
<?xml version="1.0" encoding="UTF-8"?>
<!-- <bean class="com.test.entity.Book">
	<id>12</id>
	<type>计算机</type>
    <name>Java高级编程</name>
    <author>李四</author>
    <price>33.5</price>
</bean> -->

<bean class="com.test.entity.Reader">
	<id>1</id>
    <name>李明</name>
    <score>90.5</score>
</bean>
java
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Iterator;

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

public class Test2 {
	public static void main(String[] args) {
		try {
			//1.读取xml
			SAXReader saxReader = new SAXReader();
			Document document = saxReader.read("src/bean.xml");
			Element root = document.getRootElement();
			String className = root.attributeValue("class");
			Class clazz = Class.forName(className);
			Constructor constructor = clazz.getConstructor(null);
			//2.创建对象
			Object object = constructor.newInstance(null);
			//3.给属性赋值
			Iterator<Element> rootIter = root.elementIterator();
			while(rootIter.hasNext()) {
				Element element = rootIter.next();
				String name = element.getName();
				Field field = clazz.getDeclaredField(name);
				name = "set"+name.substring(0, 1).toUpperCase()+name.substring(1);
				Method method = clazz.getMethod(name, field.getType());
				String value = element.getText();
				Object val = value;
				switch (field.getType().getName()) {
					case "int":
						val = Integer.parseInt(value);
						break;
					case "float":
						val = Float.parseFloat(value);
						break;
				}
				method.invoke(object, val);
			}
			System.out.println(object);
		} catch (DocumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SecurityException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchFieldException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

根据xml文件创建集合

xml
<?xml version="1.0" encoding="UTF-8"?>
<beans class="com.test.entity.Reader">
    <bean>
	    <id>1</id>
        <name>张三</name>
        <score>66.5</score>
    </bean>
	<bean>
	    <id>2</id>
        <name>李四</name>
        <score>80</score>
    </bean>
	<bean>
	    <id>3</id>
        <name>王五</name>
        <score>70</score>
    </bean>
</beans>
java
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

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

public class Test3 {
	public static void main(String[] args) {
		try {
			SAXReader saxReader = new SAXReader();
			Document document = saxReader.read("src/reader.xml");
			Element root = document.getRootElement();
			String className = root.attributeValue("class");
			Class clazz = Class.forName(className);
			Constructor constructor = clazz.getConstructor(null);
			List list = new ArrayList();
			Iterator<Element> rootIter = root.elementIterator();
			while(rootIter.hasNext()) {
				Element element = rootIter.next();
				Object object = constructor.newInstance(null);
				Iterator<Element> elementIter = element.elementIterator();
				while(elementIter.hasNext()) {
					Element attribute = elementIter.next();
					String name = attribute.getName();
					String value = attribute.getText();
					Field field = clazz.getDeclaredField(name);
					name = "set"+name.substring(0, 1).toUpperCase()+name.substring(1);
					Method method = clazz.getMethod(name, field.getType());
					Object val = value;
					switch (field.getType().getName()) {
						case "int":
							val = Integer.parseInt(value);
							break;
						case "float":
							val = Float.parseFloat(value);
							break;
					}
					method.invoke(object, val);
				}
				list.add(object);
			}
			for (Object object : list) {
				System.out.println(object);
			}
		} catch (DocumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SecurityException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchFieldException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
}