javaweb-day02-3（XML 解析 - Dom4j解析开发包 - XPath）

由于dom4j在获取某个节点时都得一级一级往下获，很不方便。

由于XPath表达式，获取某个节点很方便直观，所以就要由dom4j API 结合XPath表达式来获取节点，然后对节点进行某些操作。

 

  XPath快速入门，查看官方帮助文档：XPathTutorial.chm
  dom4j API 与XPath的结合，要看dom4j的docs里面的Quick Start：Powerful Navigation with XPath
  获取多个节点：Listlist = document. selectNodes ("//foo/bar");
  获取单个节点：Nodenode = document. selectSingleNode ("//foo/bar/author");

 

创建XPath需要jaxen.jar包的支持。如没有导入可能会报错：java.lang.NoClassDefFoundError: org/jaxen/JaxenException

练习一： 

book.xml

<?xml version="1.0" encoding="UTF-8"?>

<书架>
<书 name="yyyYYY">
<书名>Java就业培训教程</书名>
<售价>999</售价>
<售价>999</售价>
<作者>张孝祥</作者>
<售价>20元</售价>
<售价>20元</售价>
</书>
<书>
<书名>JavaScript网页开发</书名>
<作者>张孝祥</作者>
<售价>28.00元</售价>
</书>
</书架>

//获取第二个书名的值

@Test
public void findwithXpath() throws DocumentException{
SAXReader reader = new SAXReader();
Document document = reader.read("src/book.xml");

//获取第二个书名的值
Element ele = (Element)document.selectNodes("//书名").get(1);
System.out.println(ele.getText());
}

练习二：

users.xml

<?xml version="1.0" encoding="UTF-8"?>

<users>
<user username="lisi" password="123"></user>
<user username="wanghong" password="123"></user>
<user username="hehe" password="123"></user>
</users>

//用户登录

@Test
public void login() throws DocumentException{
SAXReader reader = new SAXReader();
Document document = reader.read("src/users.xml");

String username = "lisi";
String password = "123";

Node node = document.selectSingleNode("//user[@username='"+username+"' and @password='"+password+"']");
if(node != null){
System.out.println("登录成功！");
}else{
System.out.println("用户名或密码错误......");
}

}

练习三：用dom4j做学生成绩管理系统的重构

需求分析：

1、以如下格式的exam.xml文件为例

exam.xml

<?xml version="1.0" encoding="UTF-8"?>

<exam>
<student examid="222" idcard="111">
<name>张三</name>
<location>沈阳</location>
<grade>89.00</grade>
</student>
<student examid="444" idcard="333">
<name>李四</name>
<location>大连</location>
<grade>97.00</grade>
</student>
</exam>

２、编程实现如下功能



３、实现学生信息的添加



４、实现学生信息的查询



５、实现学生的删除功能

模块流程图：

添加数据：



查询数据：

开发顺序：

先写javabean，再写Dao用到的工具类、 Dao ，最后写界面层Main。

 

不同模块的程序，要放在不同的包里：

  实体javabean：放在domain包。
  Dao：放在dao包。dao操作xml文档必定会有重复代码：得到document、更新xml文档。将他们抽取到工具类XmlUtils里。
  工具类XmlUtils：放在utils工具包中。
  界面Main：放在main包。

 

程序源码：

package cn.mengmei.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 cn.mengmei.utils;

import java.io.FileOutputStream;
import java.io.IOException;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;

public class XMLUtils {

public static Document getDocument() throws DocumentException{
SAXReader reader = new SAXReader();
Document document = reader.read("src/exam.xml");
return document;
}

public static void write2XML(Document document) throws IOException{
OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("UTF-8");
XMLWriter writer = new XMLWriter(new FileOutputStream("src/exam.xml"),format);
writer.write(document);
writer.close();
}

}

package cn.mengmei.dao;

import java.util.Iterator;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.Node;

import cn.mengmei.domain.Student;
import cn.mengmei.utils.XMLUtils;

public class StudentDao {

public void add(Student student){
try {
Document document = XMLUtils.getDocument();
Element root = document.getRootElement();

Element stuNode = root.addElement("student");
stuNode.addAttribute("idcard", student.getIdcard());
stuNode.addAttribute("examid", student.getExamid());
stuNode.addElement("name").setText(student.getName());
stuNode.addElement("location").setText(student.getLocation());
stuNode.addElement("grade").setText(student.getGrade()+"");

XMLUtils.write2XML(document);
} catch (Exception e) {
throw new RuntimeException(e);
}
}

public void delete(String name){
try {
Document document = XMLUtils.getDocument();
List<Node> nameList = document.selectNodes("//name");

for(Iterator<Node> it=nameList.iterator(); it.hasNext(); ){
Node nameNode = it.next();
if(nameNode.getText().equals(name)){
Node stuNode = nameNode.getParent();
stuNode.getParent().remove(stuNode);
XMLUtils.write2XML(document);
return;
}
}
throw new RuntimeException("------对不起，没有查到此学生！-----");
} catch (Exception e) {
throw new RuntimeException(e);
}
}

public Student read(String examid){

try{
Document document = XMLUtils.getDocument();

Element stuNode = (Element)document.selectSingleNode("//student[@examid='"+examid+"']");
if(stuNode != null){
Student student = new Student();
student.setIdcard(stuNode.attributeValue("idcard"));
student.setExamid(stuNode.attributeValue("examid"));
student.setName(stuNode.elementText("name"));
student.setLocation(stuNode.elementText("location"));
student.setGrade(Double.parseDouble(stuNode.elementText("grade")));
return student;
}
return null;

}catch(Exception e){
throw new RuntimeException(e);
}
}
}

package cn.mengmei.main;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import cn.mengmei.dao.StudentDao;
import cn.mengmei.domain.Student;

public class Main {

public static void main(String[] args) {

System.out.println("添加用户：(a)       删除用户：(b)       查询成绩：(c)");
System.out.print("请输入操作类型：");
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String item = null;
try {
item = reader.readLine();
} catch (IOException e) {
System.out.println("-----------类型读取失败！---------");
}

Student student = null;
String idcard = null;
String examid = null;
String name = null;
String location = null;
String grade = null;
StudentDao dao = null;

switch (item) {

case "a":
try{
System.out.print("请输入学生姓名：");
name = reader.readLine();
System.out.print("请输入学生身份证号：");
idcard = reader.readLine();
System.out.print("请输入学生准考证号：");
examid = reader.readLine();
System.out.print("请输入学生所在地：");
location = reader.readLine();
System.out.print("请输入学生成绩：");
grade = reader.readLine();

student = new Student();
student.setName(name);
student.setIdcard(idcard);
student.setExamid(examid);
student.setLocation(location);
student.setGrade(Double.parseDouble(grade));

dao = new StudentDao();
dao.add(student);

System.out.println("--------添加数据成功--------");
}catch(Exception e){
System.out.println("---------对不起，添加失败！---------");
}
break;

case "b":
try{
System.out.print("请输入要删除的学生姓名：");
name = reader.readLine();
dao = new StudentDao();
dao.delete(name);
System.out.println("------已成功删除学生信息------");
}catch(Exception e){
System.out.println(e.getMessage());
}
break;

case "c":
try {
System.out.print("请输入要查询的学生准考证号：");
examid = reader.readLine();
dao = new StudentDao();
student = dao.read(examid);
if(student != null){
System.out.println("姓名："+student.getName());
System.out.println("身份证号："+student.getIdcard());
System.out.println("准考证号："+student.getExamid());
System.out.println("所在地："+student.getLocation());
System.out.println("成绩："+student.getGrade());
}else{
System.out.println("-----对不起，你要查询的学生信息不存在！-----");
}
} catch (Exception e) {
System.out.println("------对不起，查询失败！------");
}
break;

default:
System.out.println("------对不起，不支持此种操作类型！------");
break;
}
}

}