java解析xml四种方式(2)-SAX方式

java解析xml四种方式(2)-SAX方式

为解决DOM的问题，出现了SAX。SAX ，事件驱动。当解析器发现元素开始、元素结束、文本、文档的开始或结束等时，发送事件，程序员编写响应这些事件的代码，保存数据。

优点：不用事先调入整个文档，占用资源少；SAX解析器代码比DOM解析器代码小，适于Applet，下载。

缺点：不是持久的；事件过后，若没保存数据，那么数据就丢了；无状态性；从事件中只能得到文本，但不知该文本属于哪个元素；

使用场合：Applet;只需XML文档的少量内容，很少回头访问；机器内存少；  

package com.michael.xml.sax;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

/**
 * @author michael
 * 
 */
public class MySAXHandler 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("employees")) {
			return;
		}
		if (qName.equals("employee")) {
			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));
	}
}

package com.michael.xml.sax;

import java.io.FileInputStream;
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.SAXException;

import com.michael.xml.dom.XmlDocument;

/**
 * @author michael SAX文档解析
 */
public class SaxDemo implements XmlDocument {
	public void createXml(String fileName) {
		System.out.println("----" + fileName + "---");
	}

	public void parserXml(String fileName) {
		SAXParserFactory saxfac = SAXParserFactory.newInstance();
		try {
			SAXParser saxparser = saxfac.newSAXParser();
			InputStream is = new FileInputStream(fileName);
			saxparser.parse(is, new MySAXHandler());
		} 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) {
		SaxDemo demo = new SaxDemo();
		// demo.createXml("d:/michael_sax.xml");
		demo.parserXml("d:/michael.xml");
	}
}