The XML of sample code is parsed in Java using dom4j

Dom and Sax are two standard ways of parsing that already exist in Java

But it wasn't easy to operate, and for a beginner like me, some of the code was a living sickness

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

Given current trends, we'll cover the basic usage of Dom4j here, without involving complex operations such as recursion

There are many USES of Dom4j, and the examples on the website are a little obscure, so I won't write them here

First we need to create an XML document before we can parse it

XML documents:

<?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: parsing XML in the form of a List

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) {
   //If you don't know the property name
   

   //Given the property name
   System.out.println("id: " + child.attributeValue("id"));

   //Unknown child element name case
   

   //Given the name of the child element
   System.out.println("title" + child.elementText("title"));
   System.out.println("author" + child.elementText("author"));
   //This line exists for aesthetic formatting purposes
   System.out.println();
  }
 }
}

Example 2: parsing XML in the manner of an Iterator Iterator

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();

   //In the case of an unknown property name
   

   //Given the property name
   System.out.println("id: " + element.attributeValue("id"));

   //Unknown element names
   

   //Given the element name
   System.out.println("title: " + element.elementText("title"));
   System.out.println("author: " + element.elementText("author"));
   System.out.println();
  }
 }
}

Operation results:

< img Alt = "" border = 0 SRC =" / / files.jb51.net/file_images/article/201310/201310230947052.png ">

Example 3: create an XML document and output it to a 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();
  //Add a root node
  Element books = doc.addElement("books");
  //Add child element
  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");

  //Add properties for child nodes
  book1.addAttribute("id", "001");
  //Add content to the element
  title1.setText("Harry Potter");
  author1.setText("J K. Rowling");

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

  //Instantiate the output format object
  OutputFormat format = OutputFormat.createPrettyPrint();
  //Set output encoding
  format.setEncoding("UTF-8");
  //Create the File object to write to
  File file = new File("D:" + File.separator + "books.xml");
  //Generate the XMLWriter object with the parameters in the constructor as the file stream and format that you want to output
  XMLWriter writer = new XMLWriter(new FileOutputStream(file), format);
  //The write method contains the Document object created above
  writer.write(doc);
 }
}

Operation results:

< img Alt = "" border = 0 SRC =" / / files.jb51.net/file_images/article/201310/201310230947053.png ">