How to parse XML in java

DOM parsing XML

Dom parsing is to load all xml files into memory, assemble them into a dom tree, and then Parsing XML files through nodes and the relationship between nodes has nothing to do with the platform. Java provides a basic API for parsing XML files. It is relatively simple to understand, but because the entire document needs to be loaded into memory, it is not suitable for large documents. hour. (Recommended learning: java course)

SAX method to parse XML

Based on event-driven, one-by-one parsing, suitable for processing only xml data, not easy encoding, and it is difficult to access multiple different data in the same document at the same time

JDOM way to parse XML

Simplifies interaction with XML and is better than using DOM Faster to implement, using only concrete classes instead of interfaces thus simplifying the API and making it easy to parse XML using the

DOM4j way

An intelligence of JDOM Branch, more powerful, it is recommended to use

xml file proficiently

<?xml version="1.0" encoding="utf-8" ?>
<class>
    <student>
        <firstname>cxx1</firstname>
        <lastname>Bob1</lastname>
        <nickname>stars1</nickname>
        <marks>85</marks>
    </student>
    <student rollno="493">
        <firstname>cxx2</firstname>
        <lastname>Bob2</lastname>
        <nickname>stars2</nickname>
        <marks>85</marks>
    </student>
    <student rollno="593">
        <firstname>cxx3</firstname>
        <lastname>Bob3</lastname>
        <nickname>stars3</nickname>
        <marks>85</marks>
    </student>
</class>

DOM method

package com.cxx.xml;
import org.w3c.dom.*;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
/**
 * @Author: cxx
 * Dom操作xml
 * @Date: 2018/5/29 20:19
 */
public class DomDemo {
    //用Element方式
    public static void element(NodeList list){
        for (int i = 0; i <list.getLength() ; i++) {
            Element element = (Element) list.item(i);
            NodeList childNodes = element.getChildNodes();
            for (int j = 0; j <childNodes.getLength() ; j++) {
                if (childNodes.item(j).getNodeType()==Node.ELEMENT_NODE) {
                    //获取节点
                    System.out.print(childNodes.item(j).getNodeName() + ":");
                    //获取节点值
                    System.out.println(childNodes.item(j).getFirstChild().getNodeValue());
                }
            }
        }
    }
    public static void node(NodeList list){
        for (int i = 0; i <list.getLength() ; i++) {
            Node node = list.item(i);
            NodeList childNodes = node.getChildNodes();
            for (int j = 0; j <childNodes.getLength() ; j++) {
                if (childNodes.item(j).getNodeType()==Node.ELEMENT_NODE) {
                    System.out.print(childNodes.item(j).getNodeName() + ":");
                    System.out.println(childNodes.item(j).getFirstChild().getNodeValue());
                }
            }
        }
    }
    public static void main(String[] args) {
        //1.创建DocumentBuilderFactory对象
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        //2.创建DocumentBuilder对象
        try {
            DocumentBuilder builder = factory.newDocumentBuilder();
            Document d = builder.parse("src/main/resources/demo.xml");
            NodeList sList = d.getElementsByTagName("student");
            //element(sList);
            node(sList);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

SAX method

package com.cxx.xml;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
/**
 * @Author: cxx
 * SAX解析DOM
 * 一行一行  Handler
 * startElement
 * endElement
 * @Date: 2018/5/29 20:03
 */
public class SaxDemo {
    public static void main(String[] args) throws Exception {
        //1.或去SAXParserFactory实例
        SAXParserFactory factory = SAXParserFactory.newInstance();
        //2.获取SAXparser实例
        SAXParser saxParser = factory.newSAXParser();
        //创建Handel对象
        SAXDemoHandel handel = new SAXDemoHandel();
        saxParser.parse("src/main/resources/demo.xml",handel);
    }
}
class SAXDemoHandel extends DefaultHandler {
    //遍历xml文件开始标签
    @Override
    public void startDocument() throws SAXException {
        super.startDocument();
        System.out.println("sax解析开始");
    }
    //遍历xml文件结束标签
    @Override
    public void endDocument() throws SAXException {
        super.endDocument();
        System.out.println("sax解析结束");
    }
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        super.startElement(uri, localName, qName, attributes);
        if (qName.equals("student")){
            System.out.println("============开始遍历student=============");
            //System.out.println(attributes.getValue("rollno"));
        }
        else if (!qName.equals("student")&&!qName.equals("class")){
            System.out.print("节点名称:"+qName+"----");
        }
    }
    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        super.endElement(uri, localName, qName);
        if (qName.equals("student")){
            System.out.println(qName+"遍历结束");
            System.out.println("============结束遍历student=============");
        }
    }
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        super.characters(ch, start, length);
        String value = new String(ch,start,length).trim();
        if (!value.equals("")) {
            System.out.println(value);
        }
    }
}

JDOM way

<!--jdom -->
<dependency>
    <groupId>org.jdom</groupId>
    <artifactId>jdom</artifactId>
    <version>1.1.3</version>
</dependency>

package com.cxx.xml;
import org.jdom.Attribute;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.util.List;
/**
 * @Author: cxx
 * JDom解析xml
 * 快速开发XML应用程序。
 * 是一个开源项目
 * JDOM主要用来弥补DOM和SAX在实际应用当中的不足。
 * @Date: 2018/5/30 11:44
 */
public class JDomDemo {
    public static void main(String[] args) throws Exception {
        //1.创建SAXBuilder对象
        SAXBuilder saxBuilder = new SAXBuilder();
        //2.创建输入流
        InputStream is = new FileInputStream(new File("src/main/resources/demo.xml"));
        //3.将输入流加载到build中
        Document document = saxBuilder.build(is);
        //4.获取根节点
        Element rootElement = document.getRootElement();
        //5.获取子节点
        List<Element> children = rootElement.getChildren();
        for (Element child : children) {
            System.out.println("通过rollno获取属性值:"+child.getAttribute("rollno"));
            List<Attribute> attributes = child.getAttributes();
            //打印属性
            for (Attribute attr : attributes) {
                System.out.println(attr.getName()+":"+attr.getValue());
            }
            List<Element> childrenList = child.getChildren();
            System.out.println("======获取子节点-start======");
            for (Element o : childrenList) {
                System.out.println("节点名:"+o.getName()+"---"+"节点值:"+o.getValue());
            }
            System.out.println("======获取子节点-end======");
        }
    }
}

DOM4J way

 <!-- dom4j -->
 <dependency>
     <groupId>dom4j</groupId>
     <artifactId>dom4j</artifactId>
     <version>1.6.1</version>
</dependency>

package com.cxx.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.File;
import java.util.Iterator;
import java.util.List;

/**
 * @Author: cxx
 * Dom4j解析xml
 * @Date: 2018/5/30 12:21
 */
public class Dom4JDemo {
    public static void main(String[] args) throws Exception {
        //1.创建Reader对象
        SAXReader reader = new SAXReader();
        //2.加载xml
        Document document = reader.read(new File("src/main/resources/demo.xml"));
        //3.获取根节点
        Element rootElement = document.getRootElement();
        Iterator iterator = rootElement.elementIterator();
        while (iterator.hasNext()){
            Element stu = (Element) iterator.next();
            List<Attribute> attributes = stu.attributes();
            System.out.println("======获取属性值======");
            for (Attribute attribute : attributes) {
                System.out.println(attribute.getValue());
            }
            System.out.println("======遍历子节点======");
            Iterator iterator1 = stu.elementIterator();
            while (iterator1.hasNext()){
                Element stuChild = (Element) iterator1.next();
                System.out.println("节点名："+stuChild.getName()+"---节点值："+stuChild.getStringValue());
            }
        }
    }
}

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