sax解析原理与案例

package cn.itcast.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;


public class Demo1 {


/**
* @param args
* @throws SAXException 
* @throws ParserConfigurationException 
* @throws IOException 
*/
public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException {
//1.创建解析工厂
SAXParserFactory factory = SAXParserFactory.newInstance();
//2.得到解析器
SAXParser sp = factory.newSAXParser();

//3.得到读取器
XMLReader reader = sp.getXMLReader();
//4,。设置内容处理器
reader.setContentHandler(new ListHandler());
//5.读取xml文档
reader.parse("src/book.xml");


}


}
//得到xml文档所有内容
class ListHandler implements ContentHandler{


@Override
public void startElement(String uri, String localName, String name,
Attributes atts) throws SAXException {
System.out.println("<"+name+">");
for(int i=0;atts!=null && i<atts.getLength();i++){
String attName = atts.getQName(i);
String attValue = atts.getValue(i);
System.out.println(attName+"="+attValue);
}

}
@Override
public void setDocumentLocator(Locator locator) {
// TODO Auto-generated method stub

}


@Override
public void startDocument() throws SAXException {
// TODO Auto-generated method stub

}


@Override
public void endDocument() throws SAXException {
// TODO Auto-generated method stub

}


@Override
public void startPrefixMapping(String prefix, String uri)
throws SAXException {
// TODO Auto-generated method stub

}


@Override
public void endPrefixMapping(String prefix) throws SAXException {
// TODO Auto-generated method stub

}






@Override
public void endElement(String uri, String localName, String name)
throws SAXException {
System.out.println("<"+name+">");

}


@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
System.out.println(new String(ch,start,length));

}


@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 skippedEntity(String name) throws SAXException {
// TODO Auto-generated method stub

}

}

package cn.itcast.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.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;


public class Demo2 {


public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException {
//1.创建解析工厂
SAXParserFactory factory = SAXParserFactory.newInstance();
//2.得到解析器
SAXParser sp = factory.newSAXParser();

//3.得到读取器
XMLReader reader = sp.getXMLReader();
//4,。设置内容处理器
reader.setContentHandler(new TagValueHandler());
//5.读取xml文档
reader.parse("src/book.xml");


}


}
//获取标签的值
class TagValueHandler extends DefaultHandler{


private String currentTag;//记住当前解析到的是什么标签
private int needNumber = 1;//记住想获取第几个作者标签 的值
private int currentNumber;    //当前解析到第几个
@Override
public void startElement(String uri, String localName, String name,
Attributes attributes) throws SAXException {
currentTag = name;
if(currentTag.equals("作者")){
currentNumber++;
}
}


@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
currentTag = null;
}


@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
if("作者".equals(currentTag) && currentNumber==needNumber){
System.out.println(new String(ch,start,length));
}
}

}

<?xml version="1.0" encoding="UTF-8" standalone="no"?><书架>
       <书>
          <书名 name="xxxx">Java就业班培训教程</书名>
          <作者>张孝祥</作者>
          
          <售价>100元</售价>
      </书>
      <书>
          <书名>JavaScript网页开发</书名>
          <作者>黎活明</作者>
          <售价>28.00元</售价>
      </书>
</书架>