JAXP----SAX操作XML文档

1.SAX解析允许在读取文档的时候，即对文档进行处理，而不必等到整个文档装载完才会对文档进行操作！！！

sax采用事件处理方式解析XML文件，涉及解析器和事件处理器

解析器可以使用JAXP的API创建，只要解析到XML文档的一个组成部分，都会去调用事件处理器的一个方法，解析器在调用事件处理器的方法时，会把当前解析到的xml文档内容作为方法的参数传递给事件处理器！

事件处理器由程序员编写。

package it.git.sax;import java.io.IOException;import javax.xml.parsers.ParserConfigurationException;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 Demo {/* sax解析XML */public static void main(String[] args) throws ParserConfigurationException,SAXException, IOException {// 创建工厂SAXParserFactory factory = SAXParserFactory.newInstance();// 创建解析器SAXParser sp = factory.newSAXParser();// 利用解析器得到readerXMLReader xr = sp.getXMLReader();// 设置事件处理器xr.setContentHandler(new MyContentHandler());// 利用reader 读取xml文档xr.parse("src/book.xml");}}//得到xml文档内容的事件处理器class MyContentHandler implements ContentHandler {public void characters(char[] ch, int start, int length)throws SAXException {System.out.println("当前解析到了内容" + new String(ch, start, length));}public void endElement(String uri, String localName, String name)throws SAXException {System.out.println("当前解析到了" + name + ",这是一个结束标签");}public void startElement(String uri, String localName, String name,Attributes atts) throws SAXException {System.out.println("当前解析到了" + name + ",这是一个开始标签");for(int i=0; i<atts.getLength();i++){//获取标签属性String attName=atts.getQName(i);String attValue=atts.getValue(i);System.out.println(attName+"="+attValue);}}public void endDocument() throws SAXException {// TODO Auto-generated method stub}public void endPrefixMapping(String prefix) throws SAXException {// TODO Auto-generated method stub}public void ignorableWhitespace(char[] ch, int start, int length)throws SAXException {// TODO Auto-generated method stub}public void processingInstruction(String target, String data)throws SAXException {// TODO Auto-generated method stub}public void setDocumentLocator(Locator locator) {// TODO Auto-generated method stub}public void skippedEntity(String name) throws SAXException {// TODO Auto-generated method stub}public void startDocument() throws SAXException {// TODO Auto-generated method stub}public void startPrefixMapping(String prefix, String uri)throws SAXException {// TODO Auto-generated method stub}}//获取第一个节点的值class MyContentHandler2  extends DefaultHandler {    private  boolean isOk= false;    private int index=1;@Overridepublic void characters(char[] ch, int start, int length) throws SAXException {if(isOk=true&&index==1){System.out.println(new String(ch,start,length));}}@Overridepublic void endElement(String uri, String name, String attributes)throws SAXException {if(name.equals("售价")){isOk=false;}}@Overridepublic void startElement(String uri, String localName, String name,Attributes attributes) throws SAXException {if(name.equals("售价")){isOk=true;index++;}}}