xml的jaxp解析实例

实现对xml文件的增删查等操作：

package rowsy.dao;

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

import rowsy.bean.Student;
import rowsy.exception.StudentNotExistException;
import rowsy.utils.XmlUtils;

public class StudentDao {

	public void add(Student s) {
		try {
			Document document = XmlUtils.getDocument();
			
			Element studentTag = document.createElement("student");
			studentTag.setAttribute("idcard", s.getIdcard());
			studentTag.setAttribute("examid", s.getExamid());
			
			Element name = document.createElement("name");
			Element location = document.createElement("location");
			Element grade = document.createElement("grade");
			
			name.setTextContent(s.getName());
			location.setTextContent(s.getLocation());
			grade.setTextContent(s.getGrade() + "");
			
			studentTag.appendChild(name);
			studentTag.appendChild(location);
			studentTag.appendChild(grade);
			
			document.getElementsByTagName("exam").item(0).appendChild(studentTag);
			
			XmlUtils.writeToXml(document);
		} catch (Exception e) {
			// 转型 unchecked exception
			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 studentTag = (Element) list.item(i);
				if (studentTag.getAttribute("examid").equals(examid)) {
					Student s = new Student();
					
					s.setExamid(examid);
					s.setIdcard(studentTag.getAttribute("idcarg"));
					
					s.setName(studentTag.getElementsByTagName("name").item(0).getTextContent());
					s.setLocation(studentTag.getElementsByTagName("location").item(0).getTextContent());
					s.setGrade(Double.parseDouble(studentTag.getElementsByTagName("grade").item(0).getTextContent()));
					
					return s;
				}
			}
			return null;
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}
	
	public void delete(String name) throws StudentNotExistException {
		try {
			Document document = XmlUtils.getDocument();
			
			NodeList list = document.getElementsByTagName("name");
			
			for (int i = 0; i < list.getLength(); i++) {
				if (list.item(i).getTextContent().equals(name)) {
					Node node = list.item(i).getParentNode();
					node.getParentNode().removeChild(node);
					
					XmlUtils.writeToXml(document);
					
					return ;
				}
			}
			
			throw new StudentNotExistException(name + "not exist!");
		} catch (StudentNotExistException e) {
			throw e;
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}
}

xml工具类代码如下：

package rowsy.utils;

import java.io.FileOutputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;

public class XmlUtils {

	private static String filename = "src/exam.xml";
	
	public static Document getDocument() throws Exception {
		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
		DocumentBuilder builder = factory.newDocumentBuilder();
		return builder.parse(filename);
	}
	
	public static void writeToXml(Document document) throws Exception {
		TransformerFactory factory = TransformerFactory.newInstance();
		Transformer tf = factory.newTransformer();
		tf.transform(new DOMSource(document), new StreamResult(new FileOutputStream(filename)));
	}
}

 

student实体类如下：

package rowsy.bean;

public class Student {

	private String idcard;
	private String examid;
	private String name;
	private String location;
	private double grade;
	
	public String getIdcard() {
		return idcard;
	}
	public void setIdcard(String idcard) {
		this.idcard = idcard;
	}
	public String getExamid() {
		return examid;
	}
	public void setExamid(String examid) {
		this.examid = examid;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getLocation() {
		return location;
	}
	public void setLocation(String location) {
		this.location = location;
	}
	public double getGrade() {
		return grade;
	}
	public void setGrade(double grade) {
		this.grade = grade;
	}
	
}

xml文件如下：

<?xml version="1.0" encoding="UTF-8"?>
<exam>
	<student idcard="111" examid="222">
		<name>Ronnie</name>
		<location>Africa</location>
		<grade>100</grade>
	</student>
</exam>

通过对StudentDao类中函数的调用可以对xml文件中的数据进行操作