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 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,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 length)
throws SAXException {
// TODO Auto-generated method stub
System.out.println(new String(ch,length));
}
@Override
public void endElement(String uri,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 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());
}
}
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