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。
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