Four characteristics of Java parsing XML

1. DOM analysis:
forms a tree structure, which helps to better understand and master, and the code is easy to write.
During the parsing process, the tree structure is stored in memory for easy modification.

2. SAX analysis:
uses event-driven mode, which consumes less memory.
is suitable when only processing data in an XML file

3. JDOM analysis:
Only use concrete classes, not interfaces.
The API makes extensive use of the Collections class.

4. DOM4J analysis:
A smart branch of JDOM that incorporates many functions beyond the basic XML document representation.
It uses interfaces and abstract basic class methods. It has the characteristics of excellent performance, good flexibility, powerful functions and extremely easy to use.
is an open source file

Code:
First prepare a book.xml file and place it in the src directory:

<?xml version="1.0" encoding="UTF-8"?>
<books>
	<book id="1001">
		<name>Three Kingdoms</name>
		<author>Luo Guanzhong</author>
		<price>98.5</price>
	</book>
	<book id="1002">
		<name>Water Margin</name>
		<author>Shi Nai'an</author>
		<price>89.7</price>
	</book>
	<book id="1003">
		<name>Journey to the West</name>
		<author>Wu Chengen</author>
		<price>99.9</price>
	</book>
	<book id="1004">
		<name>Dream of the Red Chamber</name>
		<author>Cao Xueqin</author>
		<price>77.7</price>
	</book>
</books>

1. DOM analysis:

package com.xzlf.xml;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

/**
   * DOM parsing XML
 * @author xzlf
 *
 */
public class DOMParseTest {
	public static void main(String[] args) throws Exception {
		// 1. Create a DocumentBuilderFactory factory object
		DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
		// 2. Create DocumentBuilder object through factory object
		DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
		// 3. Get the Document object through the parse (...) method of DocumentBuilder
		Document doc = docBuilder.parse("src/book.xml");
		
		// 4. Get the list of nodes
		NodeList bookList = doc.getElementsByTagName("book");
		System.out.println(bookList.getLength());
		// Traverse node attributes
		for (int i = 0; i < bookList.getLength(); i++) {
			// Get the attributes and values ​​of each node
			Node item = bookList.item(i);
			// Get the property collection
			NamedNodeMap attributes = item.getAttributes();
			// Traverse the property collection
			for (int j = 0; j < attributes.getLength(); j++) {
				Node id = attributes.item(j);
				System.out.println(id.getNodeName() + "--" + id.getNodeValue());
			}
		}
		// Traverse the child nodes
		System.out.println("====================");
		for (int i = 0; i < bookList.getLength(); i++) {
			Node item = bookList.item(i);
			NodeList childNodes = item.getChildNodes();
			for (int j = 0; j < childNodes.getLength(); j++) {
				Node child = childNodes.item(j);
				if(child.getNodeType() == Node.ELEMENT_NODE) {
					System.out.println(child.getNodeName() + "--" + child.getTextContent());
				}
				
			}
			
		}
	}
}

run:

2. SAX analysis:

package com.xzlf.xml;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

/**
   * Sax parses xml
 * @author xzlf
 *
 */
public class SAXParseTest {
	public static void main(String[] args) throws Exception {
		// 1. Create an object of SAXParserFactory 
		SAXParserFactory saxFactory = SAXParserFactory.newInstance();
		// 2. Create SAXParser object (parser) 
		SAXParser parser = saxFactory.newSAXParser();
		// 3. Create a subclass of DefaultHandler 
		BookHandler handler = new BookHandler();
		// 4. Call the parse method 
		parser.parse("src/book.xml", handler);
	}
}

class BookHandler extends DefaultHandler{
	/*Called when starting to parse the xml document*/
	@Override
	public void startDocument() throws SAXException {
		System.out.println("BookHandler.startDocument()");
	}
	
	/*Called at the end of parsing the xml document*/
	@Override
	public void endDocument() throws SAXException {
		System.out.println("==========End of parsing document==========");
	}
	
	/*Called when starting to parse the nodes in the document*/
	@Override
	public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
		System.out.print("Start parsing element -->" + qName );
		if("book".equals(qName)) {
			System.out.println(attributes.getLength());
			for (int i = 0; i < attributes.getLength(); i++) {
				String attName = attributes.getQName(i);//Attribute name
				String attValue = attributes.getValue(i);//Attribute value
				System.out.println("Attribute name:" + attName + "Attribute value:" + attValue);
			}
		}
	}
	
	/*Called when the node in the parsing document ends*/
	@Override
	public void endElement(String uri, String localName, String qName) throws SAXException {
		System.out.println("Analyze elements-->" + qName + "End" );
	}
	
	
	@Override
	public void characters(char[] ch, int start, int length) throws SAXException {
		String values = new String(ch, start, length);
		if(!"".equals(values.trim()))
		System.out.println(values);
	}
}

run:

3. JDOM analysis:

package com.xzlf.xml;

import java.io.File;
import java.util.List;

import org.jdom.Attribute;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;

/**
   * JDOM parsing xml
   * Need to guide package: http://www.jdom.org/downloads/index.html
 * @author xzlf
 *
 */
public class JDOMParseTest {
	public static void main(String[] args) throws Exception{
		// 1. Create a SAXBuilder object 
		SAXBuilder sb = new SAXBuilder();
		// 2. Call the build method to get the Document object (via IO stream)
		Document doc = sb.build(new File("src/book.xml"));
		// 3. Get the root node 
		Element rootEle = doc.getRootElement();//books
		// 4. Get the collection of direct children of the root node 
		List<Element> children = rootEle.getChildren();
		// 5. Traverse the collection 
		for (int i = 0; i < children.size(); i++) {
			Element ele =  children.get(i);
			// Get the attribute collection
			List<Attribute> attributes = ele.getAttributes();
			// Traverse the collection of attributes to get each attribute
			for (Attribute attr : attributes) {
				System.out.println(attr.getName() + "-->" + attr.getValue());
			}
		}
		// Get every child node
		System.out.println("===========Child node==============");
		for (int i = 0; i < children.size(); i++) {
			Element book = children.get(i);
			List<Element> ele = book.getChildren();
			for (Element e : ele) {
				System.out.print(e.getName() + "-->" + e.getValue() + "\t");
			}
			System.out.println();
		}
		
	}
}

run:

4. DOM4J analysis:

package com.xzlf.xml;

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

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

/**
   * DOM4J parses XML
   * Need to guide package: https://dom4j.github.io/#looping
 * @author xzlf
 *
 */
public class DOM4JParseTest {
	public static void main(String[] args) throws DocumentException {
		// 1. Create a SAXReader object 
		SAXReader reader = new SAXReader();
		// 2. Call the read method 
		Document doc = reader.read(new File("src/book.xml"));
		// 3. Get the root element 
		Element root = doc.getRootElement();//books
		// 4. Traverse the direct node through the iterator 
		for(Iterator<Element> iterator = root.elementIterator(); iterator.hasNext();) {
			Element book = iterator.next();
			System.out.println(book.getName());
			//Get the attributes of book
			for (Iterator<Attribute> iter = book.attributeIterator(); iter.hasNext();) {
				Attribute attr = iter.next();
				System.out.println("\t" + attr.getName() + "-->" + attr.getValue());
			}
		}
		// Iterate over each book element
		for (Iterator<Element> iterator = root.elementIterator(); iterator.hasNext();) {
			Element book = iterator.next();
			//Get every child element
			for (Iterator<Element> iter = book.elementIterator(); iter.hasNext();) {
				Element ele = iter.next();
				System.out.println(ele.getName() + "-->" + ele.getText());
			}
		}
		 
	}
}

run: