SAXParser解析

优点：整个文档树在内存中，便于操作；支持删除、修改、重新排列等多种功能；

缺点：将整个文档调入内存（包括无用的节点），浪费时间和空间；使用场合：一旦解析了文档还需多次访问这些数据；硬件资源充足（内存、CPU）。 

 import java.io.ByteArrayInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

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.helpers.DefaultHandler;

/**
 * 
 * @author  panasa SAX文档解析
 */
public class SAXParserTest {

	

	public void parserXml(String fileName) {
		SAXParserFactory saxfac = SAXParserFactory.newInstance();

		try {

			SAXParser saxparser = saxfac.newSAXParser();

//			InputStream is = new FileInputStream(fileName);
//DataInput di=new DataInputStream(new InputStream() )
			InputStream   in_withcode   =   new   ByteArrayInputStream(fileName.getBytes("UTF-8"));  
			saxparser.parse(in_withcode, new UserHandler());

		} catch (ParserConfigurationException e) {

			e.printStackTrace();

		} catch (SAXException e) {

			e.printStackTrace();

		} catch (FileNotFoundException e) {

			e.printStackTrace();

		} catch (IOException e) {

			e.printStackTrace();

		}

	}

	public static void main(String []args){
		new SAXParserTest().parserXml("<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +
				"<user><name>panasa</name><sex>boy</sex><age>20</age></user>");
	}
}

class UserHandler extends DefaultHandler {
	boolean hasAttribute = false;
	Attributes attributes = null;

	public void startDocument() throws SAXException {
		System.out.println("文档开始打印了");
	}

	public void endDocument() throws SAXException {
		System.out.println("文档打印结束了");
	}

	public void startElement(String uri, String localName, String qName,
			Attributes attributes) throws SAXException {
		if (qName.equals("user")) {
			System.out.println(qName);
		}
		if (attributes.getLength() > 0) {
			this.attributes = attributes;
			this.hasAttribute = true;
		}
	}

	public void endElement(String uri, String localName, String qName)
			throws SAXException {
		if (hasAttribute && (attributes != null)) {
			for (int i = 0; i < attributes.getLength(); i++) {
				System.out.println(attributes.getQName(0)
						+ attributes.getValue(0));
			}
		}
	}

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

}