android java 文件 追加数据_【安卓学习】【xml之java拿去XMl文档节点修改添加练习】...

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【dom4j改造上面exam示列】

修改的类有StudentDom 类和JaxpUtils类剩下两个类，不许要改动，这是代码哦

【 JaxpUtils类】

package com.jack.util;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.UnsupportedEncodingException;

import org.dom4j.Document;

import org.dom4j.io.OutputFormat;

import org.dom4j.io.SAXReader;

import org.dom4j.io.XMLWriter;

//工具类

public class JaxpUtils {

//用来获取dom树

public static Document getDocument() {

//创建dom4j解析器

try{

SAXReader reader = new SAXReader();

Document document = reader.read("src/exam.xml");

return document;

}catch(Exception e){

e.printStackTrace();

}

return null;

}

//保存树到硬盘

public static void write2xml(Document document){

try {

XMLWriter writer = new XMLWriter(new FileOutputStream("src/exam.xml"),OutputFormat.createPrettyPrint());

writer.write(document);

writer.close();//保存玩关闭流

} catch (Exception e) {

e.printStackTrace();

}

}

}

【StudentDom 类】

package com.jack.dao;

import java.util.List;

import org.dom4j.Document;

import org.dom4j.Element;

import org.dom4j.Node;

import org.w3c.dom.NodeList;

import com.jack.bean.Student;

import com.jack.util.JaxpUtils;

/*

* 将学生添加到xml文件中

* student要添加的学生

* 成功返回true否则返回false

*/

//业务逻辑类

public class StudentDom {

public boolean add(Student student){

//首先加载dom树

Document document = JaxpUtils.getDocument();

//拿到根节点

Element root = document.getRootElement();

//创建一个students节点

Element stu = root.addElement("student").addAttribute("idcard", student.getIdcard())

.addAttribute("examid", student.getExamid());

//添加子节点

stu.addElement("name").setText(student.getName());

stu.addElement("location").setText(student.getLocation());

stu.addElement("grade").setText(student.getGrade()+"");

//将内存保存到硬盘

JaxpUtils.write2xml(document);

return true;

}

/*

* 根据学生姓名删除学生

*/

public boolean delete(String name){

//加载dom树

Document document = JaxpUtils.getDocument();

//获取根节点

Element root = document.getRootElement();

//拿到students节点

List stulist = root.elements("student");

//循环判断

for(int i = 0;i

Element stu = stulist.get(i);

if(stu.elementText("name").equals(name))

{

//找到了父亲干掉儿子

stu.getParent().remove(stu);

//保存结果

JaxpUtils.write2xml(document);

return true;

}

}

return false;

}

/*

*根据证考证号查询学生

*/

public Student findByExamId(String examid){

//加载dom树

Document document = JaxpUtils.getDocument();

//拿去根节点

Element root = document.getRootElement();

//拿去所有的学生节点

List stulist = root.elements("student");

//循环拿去每个stu接待你的examid熟悉进行判断

for(int i = 0;i

//找到这个学生了，开始封装了

Element stuNode = stulist.get(i);

if(stuNode.attributeValue("examid").equals(examid)){

Student s = new Student();

s.setExamid(examid);

s.setIdcard(stuNode.attributeValue("idcard"));

s.setName(stuNode.elementText("name"));

s.setLocation(stuNode.elementText("location"));

s.setGrade(Float.parseFloat(stuNode.elementText("grade")));

//保存

JaxpUtils.write2xml(document);

return s;

}

}

return null;

}

}