xml学习笔记(6)使用Dom4j对xml文档进行dom解析

xml学习笔记(6)使用Dom4j对xml文档进行dom解析

1.关于Dom4j.
    Dom4j是一个简单、灵活的开放源代码库。Dom4j是由早期开发JDOM的人分离出来而后独立开发的，与JDOM不同的是，dom4j使用接口和抽象基类，虽然Dom4j的API相对要复杂一些，但它提供了比JDOM更好的灵活性。
    Dom4j是一个非常优秀的Java XML API,具有性能优异、功能强大和极易使用的特点。现在很多软件采用Dom4j，例如Hibernate，包括sun公司自己的JAXM也用了Dom4j.
    使用Dom4j开发，需下载dom4j相应的jar文件.

    Dom4j官方网站: http://www.dom4j.org/
    Dom4j下载: http://nchc.dl.sourceforge.net/sourceforge/dom4j/dom4j-1.6.1.zip

2.Dom4j操作xml文档案例
import org.dom4j.io.SAXReader;
public class Demo1{
   //读取xml案例
   public void read() throws Exception{
      SAXReader reader = new SAXReader();
      Document document = reader.read(new File("src/book.xml"));

      Element root = document.getRootElement();
      Element book = (Element) root.elements("书").get(1);
      String value = book.element("书名").getText();
      //String value = book.element("书名").attribute("name").getValue(); //属性值
      //String value = book.element("书名").attributeValue("name");       //属性值
      System.out.println(value);

   }

   //添加xml标签.
   public void add1() throws Exception{
      SAXReader reader = new SAXReader();
      Document document = reader.read(new File("src/book.xml"));

      Element book = document.getRootElement().element("书");
      book.addElement("售价").setText("200元");

      OutputFormat format = OutputFormat.createPrettyPrint();
      format.setEncoding("UTF-8");

      XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),format));
      writer.write(document);
      writer.close();
   }

   //指定位置添加xml标签.
   public void add2() throws Exception{
      SAXReader reader = new SAXReader();
      Document document = reader.read(new File("src/book.xml"));

      Element book = document.getRootElement().element("书");
      List list = book.elements();

      Element price = DocumentHelper.createElement("售价");
      price.setText("309元");
      list.add(2, price);

      OutputFormat format = OutputFormat.createPrettyPrint();
      format.setEncoding("UTF-8");

      XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),format));
      writer.write(document);
      writer.close();
   }

   //删除xml标签.
   public void delete() throws Exception{
      SAXReader reader = new SAXReader();
      Document document = reader.read(new File("src/book.xml"));

      Element price = document.getRootElement().element("书").element("售价");
      price.getParent().remove(price);

      OutputFormat format = OutputFormat.createPrettyPrint();
      format.setEncoding("UTF-8");

      XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),format));
      writer.write(document);
      writer.close();
   }

   //更改xml标签.
   public void update() throws Exception{
      SAXReader reader = new SAXReader();
      Document document = reader.read(new File("src/book.xml"));

      Element book = (Element) document.getRootElement().elements("书").get(1);
      book.element("作者").setText("某某");
  
      OutputFormat format = OutputFormat.createPrettyPrint();
      format.setEncoding("UTF-8");

      XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),format));
      writer.write(document);
      writer.close();
   }
}

3.用XPath提取xml数据
案例1:
import java.io.File;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.io.SAXReader;
public class demo{
   public static void main(String[] args) throws DocumentException{
      SAXReader reader = new SAXReader();
      Document document = reader.read(new File("src/book.xml"));

      String value = document.selectSingleNode("//作者").getText();
      System.out.println(value);
   }
}

案例2:
import java.io.File;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.io.SAXReader;
public class demo{
   public static void main(String[] args) throws DocumentException{
      String username = "ggg";
      String password = "123";

      SAXReader reader = new SAXReader();
      Document document = reader.read(new File("src/user.xml"));

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