java通过dom读写xml文件

要读的xml文件

<?xml version="1.0" encoding="GB2312"?>
<学生花名册>
<学生性别 = "男">
<姓名>李华</姓名>
<年龄>14</年龄>
</学生>
<学生性别 = "男">
<姓名>张三</姓名>
<年龄>16</年龄>
</学生>
</学生花名册>

package xml;

import java.io.FileOutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.Iterator;
import java.util.Vector;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;

public class DomTest {
Vector students_Vector;

private Vector readXMLFile(String file) throws Exception {
  DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
  DocumentBuilder builder = dbf.newDocumentBuilder();
  Document doc = builder.parse(file); // 获取到xml文件

  // 下面开始读取
  Element root = doc.getDocumentElement(); // 获取根元素
  NodeList students = root.getElementsByTagName_r("学生");
  students_Vector = new Vector();
  for (int i = 0; i < students.getLength(); i++) {
   // 一次取得每一个学生元素
   Element ss = (Element) students.item(i);

   // 创建一个学生的实例
   student stu = new student();
   stu.setSex(ss.getAttribute("性别"));

   NodeList names = ss.getElementsByTagName_r("姓名");
   Element e = (Element) names.item(0);
   Node t = e.getFirstChild();
   stu.setName(t.getNodeValue());

   NodeList ages = ss.getElementsByTagName_r("年龄");
   e = (Element) ages.item(0);
   t = e.getFirstChild();
   stu.setAge(Integer.parseInt(t.getNodeValue()));

   students_Vector.add(stu);
  }
  return students_Vector;
}

// 写入ｘｍｌ文件
public static void callWriteXmlFile(Document doc, Writer w, String encoding) {
try {
Source source = new DOMSource(doc);

Result result = new StreamResult(w);

   Transformer xformer = TransformerFactory.newInstance()
     .newTransformer();
   xformer.setOutputProperty(OutputKeys.ENCODING, encoding);
   xformer.transform(source, result);

  } catch (TransformerConfigurationException e) {
   e.printStackTrace();
  } catch (TransformerException e) {
   e.printStackTrace();
  }
}

private void writeXMLFile(String outfile) {
  DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
  DocumentBuilder builder = null;
  try {
   builder = dbf.newDocumentBuilder();
  } catch (Exception e) {
  }
  Document doc = builder.newDocument();

Element root = doc.createElement("学生花名册");
doc.appendChild(root); // 将根元素添加到文档上

  // 获取学生信息
  for (int i = 0; i < students_Vector.size(); i++) {
   student s = (student) students_Vector.get(i);
   // 创建一个学生
   Element stu = doc.createElement("学生");
   stu.setAttribute("性别", s.getSex());
   root.appendChild(stu);// 添加属性

   // 创建文本姓名节点
   Element name = doc.createElement("姓名");
   stu.appendChild(name);
   Text tname = doc.createTextNode(s.getName());
   name.appendChild(tname);

   //创建文本年龄节点
   Element age = doc.createElement("年龄");
   stu.appendChild(age); // 将age添加到学生节点上
   Text tage = doc.createTextNode(String.valueOf(s.getAge()));
   age.appendChild(tage); // 将文本节点放在age节点上
  }
  try {
   FileOutputStream fos = new FileOutputStream(outfile);
   OutputStreamWriter outwriter = new OutputStreamWriter(fos);
   // ((XmlDocument)doc).write(outwriter); //出错！
   callWriteXmlFile(doc, outwriter, "gb2312");
   outwriter.close();
   fos.close();
  } catch (Exception e) {
   e.printStackTrace();
  }
}

public static void main(String args[]) {
  String str = "xml/student.xml";
  DomTest t = new DomTest();
  try {
   Vector v = t.readXMLFile(str);
   Iterator it = v.iterator();
   while (it.hasNext()) {
    student s = (student) it.next();
    System.out.println(s.getName() + " " + s.getAge() + " "
      + s.getSex());
   }
  } catch (Exception e) {
   e.printStackTrace();

}

String outfile = "xml/stucopy.xml";
t.writeXMLFile(outfile);

}
}

class student{
private String sex;
private String name;
private int age;

public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public void setSex(String s){sex=s;}
public String getSex(){return sex;}

public void setName(String n){name=n;}
public String getName(){return name;}
}