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对于那些比如学生信息的纯文本数据的存取，现在比较流行的是将他进行XML存放，而不是安装数据库去存放这些文字，这也算是目前XML的一个比较好的用途，本文在JAVA自带的XML解析器的基础上，实现了控制台输入命令对XML文档进行增删改查的功能，而且引入了编译异常与运行异常和异常作为返回值的内容，比较耐看，下面将代码分模块贴出。

一。Java Bean 实现对学生信息的面向对象封装

package com.bird.domain; 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; } }

package com.bird.dao; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.NodeList; import com.bid.utils.XmlUtils; import com.bird.Exception.StudentNotExitException; import com.bird.domain.Student; public class StudentDao { public void add(Student s){ try { Document document = XmlUtils.getDocument(); //创建出封装学生信息的标签 Element student_tag = document.createElement("student"); //设置属性 student_tag.setAttribute("idcard", s.getIdcard()); student_tag.setAttribute("examid", s.getExamid()); //创建用于封装学生姓名、地址和成绩的标签 Element name = document.createElement("name"); Element location = document.createElement("location"); Element grade = document.createElement("grade"); //设置内容 name.setTextContent(s.getName()); location.setTextContent(s.getLocation()); grade.setTextContent(String.valueOf(s.getGrade())); //设置他们的关系 student_tag.appendChild(name); student_tag.appendChild(location); student_tag.appendChild(grade); //把得到的根节点挂到文档上 document.getElementsByTagName("exam").item(0).appendChild(student_tag); //更新内存 XmlUtils.write2Xml(document); } catch (Exception e) { throw new RuntimeException(e);//将编译异常转换成运行时异常，方便上层想处理就处理不像处理拉到 } } public Student find(String examid){ try { Document document = XmlUtils.getDocument(); NodeList list = document.getElementsByTagName("student");//获得所有的student节点进行判断 for(int i = 0; i < list.getLength(); i++){ Element student_tag = (Element) list.item(i); if(student_tag.getAttribute("examid").equals(examid)){ //找到这个学生的信息 Student s = new Student(); s.setExamid(examid); s.setIdcard(student_tag.getAttribute("idcard")); s.setName(student_tag.getElementsByTagName("name").item(0).getTextContent()); s.setLocation(student_tag.getElementsByTagName("location").item(0).getTextContent()); s.setGrade(Double.parseDouble(student_tag.getElementsByTagName("grade").item(0).getTextContent())); return s; } } } catch (Exception e) { throw new RuntimeException(e); } return null; } public void delete(String name) throws StudentNotExitException{ 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)){ list.item(i).getParentNode().getParentNode().removeChild(list.item(i).getParentNode()); XmlUtils.write2Xml(document); return; } } throw new StudentNotExitException(name + "不存在 ！！");//编译时异常，要抛出，说明不存在，把异常当作返回值 }catch(StudentNotExitException e){ throw e; }catch (Exception e) { throw new RuntimeException(e); } } }

package com.bid.utils; import java.io.FileOutputStream; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.transform.Transformer; 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 {// 工具类所有方法都得时静态的 private static String filename = "d://exam.xml"; public static Document getDocument() throws Exception {// 获得XML的Document DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); return builder.parse(filename); } public static void write2Xml(Document doc) throws Exception {// 将更改后的XML更新到硬盘 TransformerFactory factory = TransformerFactory.newInstance(); Transformer tf = factory.newTransformer(); tf.transform(new DOMSource(doc), new StreamResult(new FileOutputStream( filename))); } }

package com.bird.Exception; public class StudentNotExitException extends Exception { /** * */ private static final long serialVersionUID = 1L; public StudentNotExitException() { // TODO Auto-generated constructor stub } public StudentNotExitException(String message) { super(message); // TODO Auto-generated constructor stub } public StudentNotExitException(Throwable cause) { super(cause); // TODO Auto-generated constructor stub } public StudentNotExitException(String message, Throwable cause) { super(message, cause); // TODO Auto-generated constructor stub } }

package com.bird.test; import com.bird.Exception.StudentNotExitException; import com.bird.dao.StudentDao; import com.bird.domain.Student; /** * @测试类 * @author Bird * */ public class DaoTest { public static void main(String[] args) throws StudentNotExitException { StudentDao dao = new StudentDao(); @SuppressWarnings("unused") Student s = new Student(); /* * s.setExamid("123"); s.setGrade(99); s.setIdcard("31234"); * s.setLocation("上海"); s.setName("鸟"); dao.add(s); */ // System.out.println(dao.find("222").getLocation()); dao.delete("张三"); } }

package com.bird.ui; import java.io.BufferedReader; import java.io.InputStreamReader; import com.bird.Exception.StudentNotExitException; import com.bird.dao.StudentDao; import com.bird.domain.Student; /** * @客户使用程序 * @author Bird * */ public class Main { public static void main(String [] args){ try{ System.out.println("添加学生（a） 删除学生(b) 查找学生(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.equals("a")){ 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 s = new Student(); s.setName(name); s.setExamid(examid); s.setGrade(Double.parseDouble(grade)); s.setIdcard(idcard); s.setLocation(location); StudentDao dao = new StudentDao(); dao.add(s); System.out.println("添加成功"); }else if(type.equals("b")){ System.out.print("请输入要删除的学生的姓名"); String namen = br.readLine(); try{ StudentDao dao = new StudentDao(); dao.delete(namen); System.out.println("删除成功"); }catch(StudentNotExitException e){ System.out.println("您要删除的学生不存在"); } }else if(type.equals("c")){ System.out.print("请输入您要查询的学生准考证号"); String num = br.readLine(); StudentDao dao = new StudentDao(); System.out.println("成绩为" + dao.find(num).getGrade()); }else{ System.out.println("对不起，不支持您的操作！！"); } }catch(Exception e){ e.printStackTrace(); System.out.println("对不起，俺出错了！！！"); } } }

麻雀虽小五脏俱全，这个小系统的模块划分和异常处理可以作为

以后大程序的典范

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