一、目标
用xml和Xapth做一个简单的数据管理系统，对数据的进行简单的增、删、改、查询操作。如做一个简单的班级学生信息管理系统：
二、环境及开发工具
环境：Java
工具：Eclipse
开发包：如图
三、原理
dom4j是一个Java的XML API，类似于jdom，用来读写XML文件的。dom4j是一个非常非常优秀的Java XML API，具有性能优异、功能强大和极端易用使用的特点，同时它也是一个开放源代码的软件，可以在SourceForge上找到它。
XPath 是一门在 XML 文档中查找信息的语言。XPath 用于在 XML 文档中通过元素和属性进行导航。XPath 使用路径表达式在 XML 文档中选取节点。节点是通过沿着路径或者 step 来选取的。
用Xpath定位到相应节点，用dom4j进行增、删、改。
四，类分析，如下图：
addframe：执行添加操作时显示的界面。
allfunction：对xml操作各功能的实现。
alterframe：执行修改操作时显示的界面。
deleteframe：执行删除操作时显示的界面。
mainframe：主界面
queryframe：执行查询操作时显示的界面。
五、主要实现如下：
import java.io.File; import java.io.FileOutputStream; import java.io.FileWriter; import java.io.IOException; import java.util.Iterator; import java.util.List; import org.dom4j.xpath.*; import javax.xml.parsers.ParserConfigurationException; import javax.xml.xpath.*; import org.dom4j.Attribute; import org.dom4j.Document; import org.dom4j.DocumentHelper; import org.dom4j.Element; import org.dom4j.io.OutputFormat; import org.dom4j.io.SAXReader; import org.dom4j.io.XMLWriter; import org.xml.sax.SAXException; /** * @author ncw * create the function */ public class allfunction { /* * 获取全部信息 */ public String getall(){ String allinformation=""; try { SAXReader saxReader = new SAXReader(); //saxReader.setEncoding("UTF-8"); Document document = saxReader.read(new java.io.File("manage.xml")); List academylist = document.selectNodes("/school/academy" ); for(int i=0;i<academylist.size();i++) { Element academyElement = (Element)academylist.get(i); allinformation=allinformation+academyElement.attribute("aid").getValue(); allinformation+=" 学院: "+"\n"; Iterator classiterator = academyElement.elementIterator("class"); while(classiterator.hasNext()) { Element classElement = (Element)classiterator.next(); allinformation+=classElement.attribute("cid").getValue(); allinformation+=" 班级: "+"\n"; Iterator studentiterator = classElement.elementIterator("student"); while(studentiterator.hasNext()) { Element studentElement=(Element)studentiterator.next(); allinformation+="姓名："; allinformation+=studentElement.elementText("name"); allinformation+=" 性别："; allinformation+=studentElement.elementText("sex"); allinformation+=" 年龄："; allinformation+=studentElement.elementText("age"); allinformation+=" 成绩："; allinformation+=studentElement.elementText("grade"); allinformation+="\n"; } } } }catch(Exception ex) { ex.printStackTrace(); } return allinformation; } /* * 获得一个学生的信息 */ public String getperson(String name) { String person=""; try { SAXReader saxReader = new SAXReader(); Document document = saxReader.read(new java.io.File("manage.xml")); List classlist = document.selectNodes("/school/academy/class" ); Iterator classiterator = classlist.iterator(); while(classiterator.hasNext()) { Element classElement = (Element)classiterator.next(); Iterator studentiterator = classElement.elementIterator("student"); while(studentiterator.hasNext()) { Element studentElement=(Element)studentiterator.next(); if(studentElement.elementText("name").equals(name)) { person+="学院："+classElement.getParent().attributeValue("aid")+"\n"; person+="班级:"+classElement.attributeValue("cid")+"\n"; person+="姓名："+studentElement.elementText("name"); person+=" 性别："+studentElement.elementText("sex"); person+=" 年龄："+studentElement.elementText("age"); person+=" 成绩："+studentElement.elementText("grade"); } } } }catch(Exception ex) { ex.printStackTrace(); } return person; } /* * 删除一个学生的信息 */ public boolean delete(String name) { boolean deleted=false; try { SAXReader saxReader = new SAXReader(); Document document = saxReader.read(new java.io.File("manage.xml")); List classlist = document.selectNodes("/school/academy/class"); Iterator classiterator = classlist.iterator(); while(classiterator.hasNext()) { Element classElement = (Element)classiterator.next(); Iterator studentiterator = classElement.elementIterator("student"); while(studentiterator.hasNext()) { Element studentElement=(Element)studentiterator.next(); if(studentElement.elementText("name").equals(name)) { classElement.remove(studentElement); deleted=true; } } } try{ /** 格式化输出,类型IE浏览一样 */ OutputFormat format = OutputFormat.createPrettyPrint(); /** 指定XML编码 */ format.setEncoding("GBK"); /** 将document中的内容写入文件中 */ // XMLWriter writer = new XMLWriter(new FileWriter(new File(newfilename)),format); //保证编码为UTF-8，支持中文写入 XMLWriter writer = new XMLWriter(new FileOutputStream(new File("manage.xml")),format); writer.write(document); writer.close(); }catch(Exception ex){ ex.printStackTrace(); } }catch(Exception ex) { ex.printStackTrace(); } return deleted; } /* * 修改一个学生的信息 */ public boolean alter(String aid,String cid,String name,String sex,String age,String grade) { boolean altered=false; try{ /* aid=new String(aid.getBytes("ISO8859-1"),"UTF-8"); cid=new String(cid.getBytes("ISO8859-1"),"UTF-8"); name=new String(name.getBytes("ISO8859-1"),"UTF-8"); sex=new String(sex.getBytes("ISO8859-1"),"UTF-8"); age=new String(age.getBytes("ISO8859-1"),"UTF-8"); grade=new String(grade.getBytes("ISO8859-1"),"UTF-8"); */ SAXReader saxReader = new SAXReader(); Document document = saxReader.read(new java.io.File("manage.xml")); List academylist = document.selectNodes("/school/academy" ); Iterator academyiterator = academylist.iterator(); while(academyiterator.hasNext()) { Element academyElement = (Element) academyiterator.next(); if(academyElement.attribute("aid").getValue().equals(aid)); Iterator classiterator = academyElement.elementIterator("class"); while(classiterator.hasNext()) { Element classElement = (Element)classiterator.next(); if(classElement.attribute("cid").getValue().equals(cid)); Iterator studentiterator = classElement.elementIterator("student"); while(studentiterator.hasNext()) { Element studentElement=(Element)studentiterator.next(); if(studentElement.elementText("name").equals(name)) { Element sexElement=studentElement.element("sex"); sexElement.setText(sex); Element ageElement=studentElement.element("age"); ageElement.setText(age); Element gradeElement=studentElement.element("grade"); gradeElement.setText(grade); altered=true; } } } } try{ /** 格式化输出,类型IE浏览一样 */ OutputFormat format = OutputFormat.createPrettyPrint(); /** 指定XML编码 */ format.setEncoding("GBK"); /** 将document中的内容写入文件中 */ // XMLWriter writer = new XMLWriter(new FileWriter(new File(newfilename)),format); //保证编码为UTF-8，支持中文写入 XMLWriter writer = new XMLWriter(new FileOutputStream(new File("manage.xml")),format); writer.write(document); writer.close(); }catch(Exception ex){ ex.printStackTrace(); } }catch(Exception ex) { ex.printStackTrace(); } return altered; } /* * 添加一个学生的信息 */ public boolean add(String aid,String cid,String name,String sex,String age,String grade) { boolean add = false; try { /* aid=new String(aid.getBytes("ISO8859-1"),"UTF-8"); cid=new String(cid.getBytes("ISO8859-1"),"UTF-8"); name=new String(name.getBytes("ISO8859-1"),"UTF-8"); sex=new String(sex.getBytes("ISO8859-1"),"UTF-8"); age=new String(age.getBytes("ISO8859-1"),"UTF-8"); grade=new String(grade.getBytes("ISO8859-1"),"UTF-8"); */ SAXReader saxReader = new SAXReader(); Document document = saxReader.read(new java.io.File("manage.xml")); List academylist = document.selectNodes("/school/academy"); Iterator academyiterator = academylist.iterator(); while (academyiterator.hasNext()) { Element academyElement = (Element) academyiterator.next(); if (academyElement.attribute("aid").getValue().equals(aid)) { Iterator classiterator = academyElement.elementIterator("class"); while (classiterator.hasNext()) { Element classElement = (Element) classiterator.next(); if (classElement.attribute("cid").getValue().equals(cid)) { Element studentElement = classElement.addElement("student"); Element nameElement = studentElement.addElement("name"); nameElement.setText(name); Element sexElement = studentElement.addElement("sex"); sexElement.setText(sex); Element ageElement = studentElement.addElement("age"); ageElement.setText(age); Element gradeElement = studentElement.addElement("grade"); gradeElement.setText(grade); add = true; } } } } try{ /** 格式化输出,类型IE浏览一样 */ OutputFormat format = OutputFormat.createPrettyPrint(); /** 指定XML编码 */ format.setEncoding("GBK"); /** 将document中的内容写入文件中 */ // XMLWriter writer = new XMLWriter(new FileWriter(new File(newfilename)),format); //保证编码为UTF-8，支持中文写入 XMLWriter writer = new XMLWriter(new FileOutputStream(new File("manage.xml")),format); writer.write(document); writer.close(); }catch(Exception ex){ ex.printStackTrace(); } }catch(Exception ex) { ex.printStackTrace(); } return add; } }
alterframe deleteframe mainframe queryframe等类则实现相应的界面显示。
相应xml结构如下：
六：总结：
1 功能简单，操作不够灵活
2 在对数据的读入与存储上有待改进。
