XML学习笔记(三)---xml解析及具体实现

概述

一个XML文件除了人去读写以外，程序也要去读写，利用程序去增删改查XML的过程就是XML编程。也就是利用程序对xml文件进行CRUD(Create、Read、Update、Delete)

两种解析思想

一张图片说明一切：

SAX解析的具体实现

package me.zipstream.sax;import javax.xml.parsers.SAXParser;import javax.xml.parsers.SAXParserFactory;import org.xml.sax.Attributes;import org.xml.sax.ContentHandler;import org.xml.sax.Locator;import org.xml.sax.SAXException;import org.xml.sax.XMLReader;import org.xml.sax.helpers.DefaultHandler;public class SaxDemo1 {    //工厂设计模式    public static void main(String[] args) throws Exception{        //1，获取解析器工厂        SAXParserFactory factory = SAXParserFactory.newInstance();        //2，通过工厂获取sax解析        SAXParser parser = factory.newSAXParser();        //3，获取读取器        XMLReader reader = parser.getXMLReader();        //4，注册事件处理器        reader.setContentHandler(new MyContentHandler2());        //5，解析xml        reader.parse("book.xml");    }}//适配器设计模式//如何获取xml文件中某一个元素上的内容呢？class MyContentHandler2 extends DefaultHandler{    private String eleName = null;    private int count = 0;    @Override    public void startElement(String uri, String localName, String name,            Attributes attributes) throws SAXException {        eleName = name;    }    @Override    public void characters(char[] ch, int start, int length)            throws SAXException {        if ("书名".equals(eleName) && (++count)==2){            System.out.println(new String(ch, start, length));        }    }    @Override    public void endElement(String uri, String localName, String name)            throws SAXException {        eleName = null;    }}class MyContentHandler implements ContentHandler{    @Override    public void startDocument() throws SAXException {        // TODO Auto-generated method stub        System.out.println("文档解析开始了...");    }    @Override    public void startElement(String uri, String localName, String name,            Attributes atts) throws SAXException {        // TODO Auto-generated method stub        System.out.println("发现了开始标签" + name);    }    @Override    public void characters(char[] ch, int start, int length)            throws SAXException {        // TODO Auto-generated method stub        System.out.println(new String(ch, start, length));    }    @Override    public void endElement(String uri, String localName, String name)            throws SAXException {        // TODO Auto-generated method stub        System.out.println("发现了结束标签" + name);    }    @Override    public void endDocument() throws SAXException {        // TODO Auto-generated method stub        System.out.println("文档解析结束了...");    }    @Override    public void endPrefixMapping(String prefix) throws SAXException {        // TODO Auto-generated method stub    }    @Override    public void ignorableWhitespace(char[] ch, int start, int length)            throws SAXException {        // TODO Auto-generated method stub    }    @Override    public void processingInstruction(String target, String data)            throws SAXException {        // TODO Auto-generated method stub    }    @Override    public void setDocumentLocator(Locator locator) {        // TODO Auto-generated method stub    }    @Override    public void skippedEntity(String name) throws SAXException {        // TODO Auto-generated method stub    }    @Override    public void startPrefixMapping(String prefix, String uri)            throws SAXException {        // TODO Auto-generated method stub    }}

DOM4J解析的具体实现

一种简单的方式：

package me.zipstream.dom4j;import org.dom4j.Document;import org.dom4j.DocumentException;import org.dom4j.Element;import org.dom4j.io.SAXReader;public class Dom4jDemo1 {    public static void main(String[] args) throws Exception {        //1，获取解析器        SAXReader reader = new SAXReader();        //2，获取代表整个文档的dom对象        Document dom = reader.read("book.xml");        //3，获取根节点        Element root = dom.getRootElement();        //4，获取书名进行打印        String bookName = root.element("书").element("书名").getText();        System.out.println(bookName);    }}

另一种方式，具体实现增删改查：

package me.zipstream.dom4j;import java.io.FileOutputStream;import java.io.OutputStreamWriter;import java.util.List;import org.dom4j.Attribute;import org.dom4j.Document;import org.dom4j.DocumentHelper;import org.dom4j.Element;import org.dom4j.io.OutputFormat;import org.dom4j.io.SAXReader;import org.dom4j.io.XMLWriter;import org.junit.Test;public class Dom4jDemo2 {    @Test    public void attr() throws Exception{        SAXReader reader = new SAXReader();        Document dom = reader.read("book.xml");        Element root = dom.getRootElement();        Element bookEle = root.element("书");        bookEle.addAttribute("出版社", "机械工业出版社");        String str = bookEle.attributeValue("出版社");        System.out.println(str);//      Attribute attr = bookEle.attribute("出版社");//      attr.getParent().remove(attr);        XMLWriter writer = new XMLWriter(new FileOutputStream("book.xml"),OutputFormat.createPrettyPrint());        writer.write(dom);        writer.close();    }    @Test    public void delete() throws Exception{        SAXReader reader = new SAXReader();        Document dom = reader.read("book.xml");        Element root = dom.getRootElement();        Element price2Ele = root.element("书").element("特价");        price2Ele.getParent().remove(price2Ele);        XMLWriter writer = new XMLWriter(new FileOutputStream("book.xml"),OutputFormat.createPrettyPrint());        writer.write(dom);        writer.close();    }    @Test    public void update() throws Exception{        SAXReader reader = new SAXReader();        Document dom = reader.read("book.xml");        Element root = dom.getRootElement();        root.element("书").element("特价").setText("4.0元");        XMLWriter writer = new XMLWriter(new FileOutputStream("book.xml"),OutputFormat.createPrettyPrint());        writer.write(dom);        writer.close();    }    @Test    public void add() throws Exception{        SAXReader reader = new SAXReader();        Document dom = reader.read("book.xml");        Element root = dom.getRootElement();        //凭空创建<特价>节点，设置标签体        Element price2Ele = DocumentHelper.createElement("特价");        price2Ele.setText("40元");        //获取父标签<书>，将特价节点挂载上去        root.element("书").add(price2Ele);        //将内存中的dom树会写到xml文件中,从而使xml中的数据进行更新        XMLWriter writer = new XMLWriter(new FileOutputStream("book.xml"), OutputFormat.createPrettyPrint());        writer.write(dom);        writer.close();    }    @Test    public void find() throws Exception{        SAXReader reader = new SAXReader();        Document dom = reader.read("book.xml");        Element root = dom.getRootElement();        List<Element> list = root.elements();        Element book2Ele = list.get(1);        System.out.println(book2Ele.element("书名").getText());    }}