Using dom4j to parse xml in java (sample code)

Although there are two standard parsing methods, Dom and Sax, in Java

, they are not easy to operate. For a beginner like me, some of the codes are disgusting.

To this end, great third-party development groups have developed tools such as Jdom and Dom4j

In view of the current trend, we will talk about the basic usage of Dom4j here, without involving complex operations such as recursion

Dom4j has many uses, and the examples on the official website are a bit obscure, so I won’t go into them here

First we need to create an xml document, and then we can parse it

xml document:

<?xml version="1.0" encoding="UTF-8"?> 
<books> 
   <book id="001"> 
      <title>Harry Potter</title> 
      <author>J K. Rowling</author> 
   </book> 
   <book id="002"> 
      <title>Learning XML</title> 
      <author>Erik T. Ray</author> 
   </book> 
</books>

Example 1: Use List to parse xml

import java.io.File;
import java.util.List;
import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
public class Demo {
 public static void main(String[] args) throws Exception {
  SAXReader reader = new SAXReader();
  File file = new File("books.xml");
  Document document = reader.read(file);
  Element root = document.getRootElement();
  List<Element> childElements = root.elements();
  for (Element child : childElements) {
   //未知属性名情况下
   /*List<Attribute> attributeList = child.attributes();
   for (Attribute attr : attributeList) {
    System.out.println(attr.getName() + ": " + attr.getValue());
   }*/

   //已知属性名情况下
   System.out.println("id: " + child.attributeValue("id"));

   //未知子元素名情况下
   /*List<Element> elementList = child.elements();
   for (Element ele : elementList) {
    System.out.println(ele.getName() + ": " + ele.getText());
   }
   System.out.println();*/

   //已知子元素名的情况下
   System.out.println("title" + child.elementText("title"));
   System.out.println("author" + child.elementText("author"));
   //这行是为了格式化美观而存在
   System.out.println();
  }
 }
}

Example 2: Use Iterator to parse xml

import java.io.File;
import java.util.Iterator;
import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
public class Demo {
 public static void main(String[] args) throws Exception {
  SAXReader reader = new SAXReader();
  Document document = reader.read(new File("books.xml"));
  Element root = document.getRootElement();

  Iterator it = root.elementIterator();
  while (it.hasNext()) {
   Element element = (Element) it.next();

   //未知属性名称情况下
   /*Iterator attrIt = element.attributeIterator();
   while (attrIt.hasNext()) {
    Attribute a  = (Attribute) attrIt.next();
    System.out.println(a.getValue());
   }*/

   //已知属性名称情况下
   System.out.println("id: " + element.attributeValue("id"));

   //未知元素名情况下
   /*Iterator eleIt = element.elementIterator();
   while (eleIt.hasNext()) {
    Element e = (Element) eleIt.next();
    System.out.println(e.getName() + ": " + e.getText());
   }
   System.out.println();*/

   //已知元素名情况下
   System.out.println("title: " + element.elementText("title"));
   System.out.println("author: " + element.elementText("author"));
   System.out.println();
  }
 }
}

Running results:

Example 3: Create xml document and output to file

import java.io.File;
import java.io.FileOutputStream;
import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.XMLWriter;

public class Demo {
 public static void main(String[] args) throws Exception {
  Document doc = DocumentHelper.createDocument();
  //增加根节点
  Element books = doc.addElement("books");
  //增加子元素
  Element book1 = books.addElement("book");
  Element title1 = book1.addElement("title");
  Element author1 = book1.addElement("author");

  Element book2 = books.addElement("book");
  Element title2 = book2.addElement("title");
  Element author2 = book2.addElement("author");

  //为子节点添加属性
  book1.addAttribute("id", "001");
  //为元素添加内容
  title1.setText("Harry Potter");
  author1.setText("J K. Rowling");

  book2.addAttribute("id", "002");
  title2.setText("Learning XML");
  author2.setText("Erik T. Ray");

  //实例化输出格式对象
  OutputFormat format = OutputFormat.createPrettyPrint();
  //设置输出编码
  format.setEncoding("UTF-8");
  //创建需要写入的File对象
  File file = new File("D:" + File.separator + "books.xml");
  //生成XMLWriter对象，构造函数中的参数为需要输出的文件流和格式
  XMLWriter writer = new XMLWriter(new FileOutputStream(file), format);
  //开始写入，write方法中包含上面创建的Document对象
  writer.write(doc);
 }
}

Run result:

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