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 exceptionthrow 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