Books.xml file content

<?xml version="1.0" encoding="UTF-8"?>
<bookstore>
	<book id="1">
		<name>Song of Ice and Fire</name>
		 <author>George Martin</author>
		<year>2014</year>
		<price>89</price>
	</book>
	<book id="2">
		 <name>Andersen's Fairy Tales</name>
		<year>2004</year>
		<price>77</price>
		<language>English</language>
	</book>
</bookstore>

1. DOM analysis, officially provided, load the xml file into the memory at a time, it is not efficient to support the xml file is too large

public static void main(String[] args) {

        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        try {
            DocumentBuilder db = dbf.newDocumentBuilder();
            Document document = db.parse("books.xml");
            NodeList books = document.getElementsByTagName("book");
            for(int i = 0;i<books.getLength();i++){
                                 System.out.println("Start to traverse the first"+(i+1)+"book");
                Element book = (Element) books.item(i);
                String id = book.getAttribute("id");
                System.out.println("id:"+id);
                NodeList nodeList = books.item(i).getChildNodes();
                for(int j = 0;j<nodeList.getLength();j++){
                    if(nodeList.item(j).getNodeType()==Node.ELEMENT_NODE){
                        System.out.println(nodeList.item(j).getNodeName()+":"+nodeList.item(j).getTextContent());
                    }
                }
            }
        } catch (ParserConfigurationException e) {
            e.printStackTrace();
        } catch (SAXException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

2. SAX way of analysis, officially provided, read the nodes of the xml file one by one, for larger xml files, good support, use the interface to inherit the DefaultHandler interface

package com.example.xml;

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

import java.util.ArrayList;
import java.util.List;

public class SAXParserHandler extends DefaultHandler {
    Book book = null;
    String value = null;
    List<Book> books = new ArrayList<>();

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        super.startElement(uri, localName, qName, attributes);
        if(qName.equals("book")){
            book = new Book();
            for(int i =0;i<attributes.getLength();i++){
                if(attributes.getQName(i).equals("id")){
                    book.setId(attributes.getValue(i));
                }
                System.out.println(attributes.getQName(i)+":"+attributes.getValue(i));
            }
        }else if(!qName.equals("bookstore")){
            System.out.print(qName+":");
        }
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        super.endElement(uri, localName, qName);
        if(qName.equals("book")){
            books.add(book);
            book = null;
        }else if(qName.equals("name")){
            book.setName(value);
        }else if(qName.equals("author")){
            book.setAuthor(value);
        }else if(qName.equals("year")){
            book.setYear(value);
        }else if(qName.equals("price")){
            book.setPrice(value);
        }else if(qName.equals("language")){
            book.setLanguage(value);
        }
    }


    @Override
    public void startDocument() throws SAXException {
        super.startDocument();
                 System.out.println("SAX analysis start");
    }

    @Override
    public void endDocument() throws SAXException {
        super.endDocument();
                 System.out.println("SAX parsing end");
    }

    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        super.characters(ch, start, length);
        value = new String(ch,start,length);
        if(!value.trim().equals("")){
            System.out.println(value);
        }
    }

    public List<Book> getBooks() {
        return books;
    }
}

@Test
    public  void Sax() throws IOException, ParserConfigurationException, SAXException {
        SAXParserFactory saxParserFactory = SAXParserFactory.newInstance();
        SAXParser saxParser = saxParserFactory.newSAXParser();
        SAXParserHandler saxParserHandler = new SAXParserHandler();
        saxParser.parse("books.xml", saxParserHandler);
        List<Book> books = saxParserHandler.getBooks();
        for(Book book:books){
            System.out.println(book);
        }
    }

3. JDOM analysis, provided by the third party

package com.example.xml;

import org.jdom2.Attribute;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.JDOMException;
import org.jdom2.input.SAXBuilder;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

public class JDOMTest {

    public static void main(String[] args) throws IOException, JDOMException {
        SAXBuilder saxBuilder = new SAXBuilder();
        FileInputStream fileInputStream = new FileInputStream(new File("books.xml"));
        InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream,"utf-8");
        Document document = saxBuilder.build(inputStreamReader);
        Element rootElement = document.getRootElement();
        List<Element> elements = rootElement.getChildren();
        List<Book> bookEntites = new ArrayList<>();
        for(Element element:elements){
            Book bookEntity = new Book();
            List<Attribute> attributes = element.getAttributes();
            for(Attribute attr:attributes){
                if(attr.getName().equals("id")){
                    bookEntity.setId(attr.getValue());
                }
                System.out.println(attr.getName()+"-----------"+attr.getValue());
            }
            List<Element> books = element.getChildren();
            for(Element book:books){
                String name = book.getName();
                String value = book.getValue();
                if(name.equals("name")){
                    bookEntity.setName(value);
                }else if(name.equals("author")){
                    bookEntity.setAuthor(value);
                }else if(name.equals("year")){
                    bookEntity.setYear(value);
                }else if(name.equals("price")){
                    bookEntity.setPrice(value);
                }else if(name.equals("language")){
                    bookEntity.setLanguage(value);
                }
                System.out.println(name+"--------"+value);
            }
            bookEntites.add(bookEntity);
        }

        System.out.println("====================================================================");
        for(Book book:bookEntites){
            System.out.println(book);
        }

    }
}

4. DOM4J analysis, provided by a third party, relatively simple to use, relatively efficient, and widely used

package com.example.xml;

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

import java.io.*;
import java.util.Iterator;
import java.util.List;

public class DOM4JTest {

    public static void main(String[] args) throws DocumentException, FileNotFoundException, UnsupportedEncodingException {

        SAXReader saxReader = new SAXReader();
        InputStreamReader inputStreamReader = new InputStreamReader(new FileInputStream("books.xml"),"utf-8");
        Document document = saxReader.read(inputStreamReader);
        Element rootElement = document.getRootElement();
        Iterator iterator = rootElement.elementIterator();
        while (iterator.hasNext()){
            Element element = (Element) iterator.next();
            List<Attribute> attributes = element.attributes();
            for(Attribute attr:attributes){
                System.out.println(attr.getName()+"---------------"+attr.getValue());
            }
            List<Element> books = element.elements();
            for (Element element1:books){
                System.out.println(element1.getName()+"---------------"+element1.getStringValue());
            }
        }

    }
}