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How to parse XML in java

Nov 13, 2019 am 10:20 AM
java

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) {
                    //獲取節(jié)點(diǎn)
                    System.out.print(childNodes.item(j).getNodeName() + ":");
                    //獲取節(jié)點(diǎn)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.創(chuàng)建DocumentBuilderFactory對(duì)象
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        //2.創(chuàng)建DocumentBuilder對(duì)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實(shí)例
        SAXParserFactory factory = SAXParserFactory.newInstance();
        //2.獲取SAXparser實(shí)例
        SAXParser saxParser = factory.newSAXParser();
        //創(chuàng)建Handel對(duì)象
        SAXDemoHandel handel = new SAXDemoHandel();
        saxParser.parse("src/main/resources/demo.xml",handel);
    }
}
class SAXDemoHandel extends DefaultHandler {
    //遍歷xml文件開始標(biāo)簽
    @Override
    public void startDocument() throws SAXException {
        super.startDocument();
        System.out.println("sax解析開始");
    }
    //遍歷xml文件結(jié)束標(biāo)簽
    @Override
    public void endDocument() throws SAXException {
        super.endDocument();
        System.out.println("sax解析結(jié)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("============開始遍歷student=============");
            //System.out.println(attributes.getValue("rollno"));
        }
        else if (!qName.equals("student")&&!qName.equals("class")){
            System.out.print("節(jié)點(diǎn)名稱:"+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+"遍歷結(jié)束");
            System.out.println("============結(jié)束遍歷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
 * 快速開發(fā)XML應(yīng)用程序。
 * 是一個(gè)開源項(xiàng)目
 * JDOM主要用來彌補(bǔ)DOM和SAX在實(shí)際應(yīng)用當(dāng)中的不足。
 * @Date: 2018/5/30 11:44
 */
public class JDomDemo {
    public static void main(String[] args) throws Exception {
        //1.創(chuàng)建SAXBuilder對(duì)象
        SAXBuilder saxBuilder = new SAXBuilder();
        //2.創(chuàng)建輸入流
        InputStream is = new FileInputStream(new File("src/main/resources/demo.xml"));
        //3.將輸入流加載到build中
        Document document = saxBuilder.build(is);
        //4.獲取根節(jié)點(diǎn)
        Element rootElement = document.getRootElement();
        //5.獲取子節(jié)點(diǎn)
        List<Element> children = rootElement.getChildren();
        for (Element child : children) {
            System.out.println("通過rollno獲取屬性值:"+child.getAttribute("rollno"));
            List<Attribute> attributes = child.getAttributes();
            //打印屬性
            for (Attribute attr : attributes) {
                System.out.println(attr.getName()+":"+attr.getValue());
            }
            List<Element> childrenList = child.getChildren();
            System.out.println("======獲取子節(jié)點(diǎn)-start======");
            for (Element o : childrenList) {
                System.out.println("節(jié)點(diǎn)名:"+o.getName()+"---"+"節(jié)點(diǎn)值:"+o.getValue());
            }
            System.out.println("======獲取子節(jié)點(diǎn)-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.創(chuàng)建Reader對(duì)象
        SAXReader reader = new SAXReader();
        //2.加載xml
        Document document = reader.read(new File("src/main/resources/demo.xml"));
        //3.獲取根節(jié)點(diǎn)
        Element rootElement = document.getRootElement();
        Iterator iterator = rootElement.elementIterator();
        while (iterator.hasNext()){
            Element stu = (Element) iterator.next();
            List<Attribute> attributes = stu.attributes();
            System.out.println("======獲取屬性值======");
            for (Attribute attribute : attributes) {
                System.out.println(attribute.getValue());
            }
            System.out.println("======遍歷子節(jié)點(diǎn)======");
            Iterator iterator1 = stu.elementIterator();
            while (iterator1.hasNext()){
                Element stuChild = (Element) iterator1.next();
                System.out.println("節(jié)點(diǎn)名:"+stuChild.getName()+"---節(jié)點(diǎn)值:"+stuChild.getStringValue());
            }
        }
    }
}

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