xml文件的读写

dom4j读写，用dom4j更改xml文件的数据实际是一个查询更新的过程。

import java.io.File;
import java.io.FileWriter;
import java.util.Iterator;

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;

public class dom4jTest {
    public void XMLWriter(){
        try {
            XMLWriter writer = null;// 声明写XML的对象
            SAXReader reader = new SAXReader();

            OutputFormat format = OutputFormat.createPrettyPrint();
            format.setEncoding("UTF-8");// 设置XML文件的编码格式

            String filePath = "src/test.xml";
            File file = new File(filePath);

            if (file.exists()) {/**验证文件是否存在*/
                Document document = reader.read(file);// 读取XML文件
                Element root = document.getRootElement();// 得到根节点

                // 添加一个学生信息
                Element student = root.addElement("user");
                student.addAttribute("id", "001");
                Element code = student.addElement("code");
                code.setText("100");
                Element name = student.addElement("name");
                name.setText("张三");
                Element sex = student.addElement("sex");
                sex.setText("男");
                Element age = student.addElement("age");
                age.setText("21");

                writer = new XMLWriter(new FileWriter(filePath), format);
                writer.write(document);
                writer.close();
            } else {
                // 新建student.xml文件并新增内容
                Document document = DocumentHelper.createDocument();
                Element root = document.addElement("userinfo");
                Element student = root.addElement("user");
                student.addAttribute("id", "001");
                Element code = student.addElement("code");
                code.setText("100");
                Element name = student.addElement("name");
                name.setText("张三");
                Element sex = student.addElement("sex");
                sex.setText("男");
                Element age = student.addElement("age");
                age.setText("21");

                writer = new XMLWriter(new FileWriter(file), format);
                writer.write(document);
                writer.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public void XMLRead(){
        try{
             SAXReader reader = new SAXReader();
            Document document = reader.read(new File("src/test.xml"));
            Element root = document.getRootElement();
            for (Iterator i = root.elements("user").iterator(); i.hasNext();) {
                Element user = (Element) i.next();
                String code = user.element("code").getText();
                String name = user.element("name").getText();
                String sex = user.element("sex").getText();
                String age = user.element("age").getText();;

                System.out.print(code+","+name+","+sex+","+age);
            }
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

xml文件

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

<userinfo>
  <user id="001">
    <code>100</code>
    <name>张三</name>
    <sex>男</sex>
    <age>21</age>
  </user>
</userinfo>