Java XML解析之SAX解析

SAX（Simple API for XML）解析：基于事件流的解析。

特点：速度快，文档大小无限制

只读，不能随机访问，不好查找节点

java包：org.xml.sax/org.xml.sax.helpers

常用接口/类：

XMLReader

ContentHandler

DTDHandler

EntityResolver

ErrorHandler

DefaultHandler

DefaultHandler事件举例：

startDocument():

startElement(String uri, String localName, String qName,Attributes attributes)

characters(char[] ch, int start, int length)

endElement(String uri, String localName, String qName)

编程步骤：

1.准备一个xml文件，和DOM解析一样，movies.xml:

<?xml version="1.0" encoding="UTF-8"?>
<Movies>
    <Movie id="1">
        <name>愤怒的小鸟</name>
        <type>animation</type>
        <year>2016</year>
    </Movie>
    <Movie id="2">
        <name>叶问</name>
        <type>action</type>
        <language>chinese</language>
    </Movie>
</Movies>

2.创建SAXParserFactory对象

SAXParserFactory spf=SAXParserFactory.newInstance();

3.创建SAXParser对象

SAXParser saxParser=spf.newSAXParser();

4.解析处理xml文件

saxParser.parse("movies.xml", new MyHandler());

5.然后会在MyHandler处理xml文件

这个类继承了DefaultHandler，下面开始讲解步骤：

（1）开始xml解析：

@Override
	public void startDocument() throws SAXException {
		// TODO Auto-generated method stub
		System.out.println("开始解析");
		movielist=new ArrayList<Movie>();
	}

（2）开始解析每一部电影：

        @Override
	public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
		// TODO Auto-generated method stub
		if(qName.equals("Movie")){
			movie=new Movie();
			count++;
			System.out.println("正在解析第"+count+"部电影");
			for(int i=0;i<attributes.getLength();i++){
				System.out.println("属性名:"+attributes.getQName(i));
				System.out.println("属性值:"+attributes.getValue(i));
				if(attributes.getQName(i).equals("id")){
					movie.setId(attributes.getValue(i));
				}
			}
		}
	}

（3）开始解析每一部电影的节点值：

	@Override
	public void characters(char[] ch, int start, int length) throws SAXException {
		// TODO Auto-generated method stub
		value=new String(ch,start,length);
		if(!value.trim().equals("")){//去除空格之后不是空字符串
		System.out.println("节点值:"+value);
	   }
	}

（4）结束解析每一部电影：

	
	@Override
	public void endElement(String uri, String localName, String qName) throws SAXException {
		// TODO Auto-generated method stub
		if(qName.equals("Movie")){
			movielist.add(movie);
			movie=null;
			System.out.println("第"+count+"部电影解析结束");
		}
		if(qName.equals("year")){
			movie.setYear(value);
		}else if (qName.equals("name")) {
	        movie.setName(value);		
		}else if (qName.equals("language")) {
			movie.setLanguage(value);
		}else if (qName.equals("type")) {
			movie.setYear(value);
		}
	}

（6）结束xml解析：

	@Override
	public void endDocument() throws SAXException {
		// TODO Auto-generated method stub
		System.out.println("结束解析");
	}

6.MyHandler完整代码：

public class MyHandler extends DefaultHandler{

	private String value;
	private int count=0;
	private Movie movie;
	private ArrayList<Movie>movielist;
	@Override
	public void startDocument() throws SAXException {
		// TODO Auto-generated method stub
		System.out.println("开始解析");
		movielist=new ArrayList<Movie>();
	}
	
	@Override
	public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
		// TODO Auto-generated method stub
		if(qName.equals("Movie")){
			movie=new Movie();
			count++;
			System.out.println("正在解析第"+count+"部电影");
			for(int i=0;i<attributes.getLength();i++){
				System.out.println("属性名:"+attributes.getQName(i));
				System.out.println("属性值:"+attributes.getValue(i));
				if(attributes.getQName(i).equals("id")){
					movie.setId(attributes.getValue(i));
				}
			}
		}
	}
	
	
	@Override
	public void characters(char[] ch, int start, int length) throws SAXException {
		// TODO Auto-generated method stub
		value=new String(ch,start,length);
		if(!value.trim().equals("")){//去除空格之后不是空字符串
		System.out.println("节点值:"+value);
	   }
	}
	
	@Override
	public void endElement(String uri, String localName, String qName) throws SAXException {
		// TODO Auto-generated method stub
		if(qName.equals("Movie")){
			movielist.add(movie);
			movie=null;
			System.out.println("第"+count+"部电影解析结束");
		}
		if(qName.equals("year")){
			movie.setYear(value);
		}else if (qName.equals("name")) {
	        movie.setName(value);		
		}else if (qName.equals("language")) {
			movie.setLanguage(value);
		}else if (qName.equals("type")) {
			movie.setYear(value);
		}
	}
	
	@Override
	public void endDocument() throws SAXException {
		// TODO Auto-generated method stub
		System.out.println("结束解析");
	}
}

7.Sax：

public class Sax {

	public static void main(String[] args) {
		//1.创建SAXParserFactory对象
		SAXParserFactory spf=SAXParserFactory.newInstance();
		try {
			//2.创建SAXParser对象
			SAXParser saxParser=spf.newSAXParser();
			saxParser.parse("movies.xml", new MyHandler());
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

8.Movie：

public class Movie {


	private String id,name,type,language,year;

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getType() {
		return type;
	}

	public void setType(String type) {
		this.type = type;
	}

	public String getLanguage() {
		return language;
	}

	public void setLanguage(String language) {
		this.language = language;
	}

	public String getYear() {
		return year;
	}

	public void setYear(String year) {
		this.year = year;
	}
	@Override
	public String toString() {
		// TODO Auto-generated method stub
		return "id:"+id+" "+"name:"+name+" "+"type:"+type+" "+"language:"+language+" "
				+"year:"+year;
	}
}

效果图：