XML解析

程序员文章站 2022-04-30 10:00:11

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XML文件解析

首先我以“学生信息”举例，给一个xml文件的代码：
student.tag.xml

<?xml version="1.0" encoding="UTF-8"?>
<students>
	<student>
		<id>00001</id>
		<name>小张</name>
		<sex>男</sex>
		<birtdhday>2000-10-3</birtdhday>
		<hobbies>
			<hobby>游泳</hobby>
			<hobby>装逼</hobby>
			<hobby>睡觉</hobby>
		</hobbies>
		<introduce>
			无所事事的小混混；
		</introduce>
	</student>
	<student>
		<id>00002</id>
		<name>晓珊</name>
		<sex>女</sex>
		<birtdhday>2001-1-21</birtdhday>
		<hobbies>
			<hobby>游泳</hobby>
			<hobby>画画</hobby>
			<hobby>学习</hobby>
		</hobbies>
		<introduce>
			琴棋书画样样精通；
		</introduce>
	</student>
</students>

再给另一个xml文件：
student.att.xml

<?xml version="1.0" encoding="UTF-8"?>
<students>
	<student id="00001" name="小张" sex="男" birtdhday="2000-10-3">
		<hobby>游泳</hobby>
		<hobby>装逼</hobby>
		<hobby>睡觉</hobby>
		<introduce>
			无所事事的小混混；
		</introduce>
	</student>
	<student id="00002" name="晓珊" sex="女" birtdhday="2001-1-21">
		<hobbies>
			<hobby>游泳</hobby>
			<hobby>画画</hobby>
			<hobby>学习</hobby>
		</hobbies>
		<introduce>
			琴棋书画样样精通；
		</introduce>
	</student>
</students>

前一种着重使用标签，第二种方式综合属性和标签。这两种都可以表达学生信息，没有哪种是标准方式。

分别给出两个xml文件的解析类：
TestParseTag.java

package com.mec.about_xml.test;

import java.io.IOException;
import java.io.InputStream;

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

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class TestParseTag {

	public static void main(String[] args) {
		try {
			InputStream is = TestParseTag.class.getResourceAsStream("/student.tag.xml");
			DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
			DocumentBuilder db = dbf.newDocumentBuilder();
			Document document = db.parse(is);
			
			NodeList studentList =  document.getElementsByTagName("student");
			for (int index = 0; index < studentList.getLength(); index++) {
				Element student = (Element) studentList.item(index);
				Element idElement = (Element) student.getElementsByTagName("id").item(0);
				String id = idElement.getTextContent();
				
				Element nameElement = (Element) student.getElementsByTagName("name").item(0);
				String name = nameElement.getTextContent();
				
				Element introduceElement = (Element) student.getElementsByTagName("introduce").item(0);
				String introduce = introduceElement.getTextContent();
				
				System.out.println(id + ", " + name);
				System.out.println("[" + introduce.trim() + "]");
			}
		} catch (ParserConfigurationException e) {
			e.printStackTrace();
		} catch (SAXException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}

TestParseAttribute.java

package com.mec.about_xml.test;

import java.io.IOException;
import java.io.InputStream;

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

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

import com.mec.about_xml.model.StudentInfo;

public class TestParseAttribute {

	public static void main(String[] args) {
		try {
			InputStream is = TestParseAttribute.class.getResourceAsStream("/student.att.xml");
			DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
			DocumentBuilder db = dbf.newDocumentBuilder();
			Document document = db.parse(is);
			
			NodeList studentList = document.getElementsByTagName("student");
			for (int i = 0; i < studentList.getLength(); i++) {
				StudentInfo stu = new StudentInfo();
				
				Element student = (Element) studentList.item(i);
				String id = student.getAttribute("id");
				String name = student.getAttribute("name");
				String sex = student.getAttribute("sex");
				String birthday = student.getAttribute("birtdhday");
				
				NodeList hobbyList = student.getElementsByTagName("hobby");
				for (int j = 0; j < hobbyList.getLength(); j++) {
					Element hobby = (Element) hobbyList.item(0);
					String hobbyString = hobby.getTextContent();
					stu.addHobby(hobbyString);
				}
				
				stu.setId(id);
				stu.setName(name);
				stu.setSex(sex);
				stu.setBirthday(birthday);
				
				String introduce = student.getElementsByTagName("introduce")
						.item(0).getTextContent().trim();
				stu.setIntroduce(introduce);
				
				System.out.println(stu);
			}
		} catch (ParserConfigurationException e) {
			e.printStackTrace();
		} catch (SAXException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}

观察上面的两个解析类：TestParseTag类和TestParseAttribute类；我们发现这两个解析类有很多的相似之处。
例如：

			DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
			DocumentBuilder db = dbf.newDocumentBuilder();
			InputStream is = TestParseAttribute.class.getResourceAsStream("/student.att.xml");
			Document document = db.parse(is);

这四行代码可以认为是一个固定套路。而且从最后一行可以看出前两行代码就是要得到一个DocumentBuilder类的对象，而且，对于不同的XML文件解析，这个对象只需要一个就够了！
我们就可以将XML解析过程“工具化”。

XML文件解析过程的工具化

这里先引入一个概念——静态块；
静态块的特点是在类加载的时候就执行，且只执行一次，以后不再执行。

下面我给出XMLParse.java

package com.mec.util;

import java.io.IOException;
import java.io.InputStream;

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

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public abstract class XMLParser {
	private static final DocumentBuilderFactory dbf;
	private static DocumentBuilder db;
	static {
		dbf = DocumentBuilderFactory.newInstance();
		try {
			db = dbf.newDocumentBuilder();
		} catch (ParserConfigurationException e) {
			e.printStackTrace();
		}
	}
	
	public XMLParser() {
	}
	
	public static Document getDocument(String xmlPath) {
		InputStream is = XMLParser.class.getResourceAsStream(xmlPath);
		if (is == null) {
			System.out.println("xmlPath[" + xmlPath + "]不存在！");
			return null;
		}
		
		return getDocument(is);
	}
	
	public static Document getDocument(InputStream is) {
		Document document = null;
		try {
			document = db.parse(is);
		} catch (SAXException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
		return document;
	}
	
	public abstract void dealElement(Element element, int index);
	
	public void parseTag(Document document, String tagName) {
		NodeList nodeList = document.getElementsByTagName(tagName);
		for (int index = 0; index < nodeList.getLength(); index++) {
			Element ele = (Element) nodeList.item(index);
			dealElement(ele, index);
		}
	}
	
	public void parseTag(Element element, String tagName) {
		NodeList nodeList = element.getElementsByTagName(tagName);
		for (int index = 0; index < nodeList.getLength(); index++) {
			Element ele = (Element) nodeList.item(index);
			dealElement(ele, index);
		}
	}
	
}

编写调用XMLParse.java的类Test：
首先，先建立辅助我们解析XML文件的类：StudentInfo.java

package com.mec.about_xml.model;

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

public class StudentInfo {
	private String id;
	private String name;
	private String sex;
	private String birthday;
	private String introduce;
	private List<String> hobbies;
	
	public StudentInfo() {
		hobbies = new ArrayList<String>();
	}

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public String getBirthday() {
		return birthday;
	}

	public void setBirthday(String birthday) {
		this.birthday = birthday;
	}

	public String getIntroduce() {
		return introduce;
	}

	public void setIntroduce(String introduce) {
		this.introduce = introduce;
	}

	public List<String> getHobbies() {
		return hobbies;
	}
	
	public void addHobby(String hobby) {
		if (hobbies.contains(hobby)) {
			return;
		}
		hobbies.add(hobby);
	}

	@Override
	public String toString() {
		StringBuffer res = new StringBuffer();
		
		res.append(id).append(" ")
			.append(sex).append(" ")
			.append(name).append(" ")
			.append(birthday).append(" 简介:")
			.append(introduce).append("\n");
		for (String hobby : hobbies) {
			res.append('\t').append(hobby).append("\n");
		}
		
		return res.toString();
	}
	
}

Test.java

package com.mec.about_xml.test;

import org.w3c.dom.Element;

import com.mec.about_xml.model.StudentInfo;
import com.mec.util.XMLParser;

public class Test {

	public static void main(String[] args) {
		new XMLParser() {
			@Override
			public void dealElement(Element element, int index) {
				StudentInfo stu = new StudentInfo();
				
				String id = element.getAttribute("id");
				stu.setId(id);
				String name = element.getAttribute("name");
				stu.setName(name);
				String sex = element.getAttribute("sex");
				stu.setSex(sex);
				String birthday = element.getAttribute("birtdhday");
				stu.setBirthday(birthday);
				
				new XMLParser() {
					@Override
					public void dealElement(Element element, int index) {
						String hobbyString = element.getTextContent();
						stu.addHobby(hobbyString);
					}
				}.parseTag(element, "hobby");
				
				new XMLParser() {
					@Override
					public void dealElement(Element element, int index) {
						String introduce = element.getTextContent().trim();
						stu.setIntroduce(introduce);
					}
				}.parseTag(element, "introduce");
				
				System.out.println(stu);
			}
		}.parseTag(XMLParser.getDocument("/student.att.xml"), "student");
	}

}

结果显示：
XML解析
我们可以把我们的工具类打成jar包，方便以后我们的调用。

相关标签： XML文件解析静态块

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