java 中的SAX解析XML的使用(一)

读取的XML文件如下:

<?xml version="1.0" encoding="UTF-8"?>
<books>
	<book id="1">
		<name>Thinking in java</name>
		<price>89</price>
	</book>
	<book id="3">
		<name>Spring in Action</name>
		<price>46</price>
	</book>
	<book id="9">
		<name>Java Web development start</name>
		<price>12</price>
	</book>
</books>

public class SAXTest {
		
	public static void main(String[] args) throws Exception {
		// TODO Auto-generated method stub
		getBooks();
	}
	
	public static void getBooks() throws Exception
	{
		List<Book> books = new ArrayList<Book>();//保存book
		SAXParserFactory saxFactory = SAXParserFactory.newInstance();//sax转换工厂类
		SAXParser parser =  saxFactory.newSAXParser();//创建一个新的转换器
		//文件输入流
		FileInputStream fi =  new FileInputStream(SAXTest.class.getClassLoader().getResource("Test.xml").getPath());
		SAXHandler handler = new SAXHandler(books);//xml处理类
		parser.parse(fi, handler);//读取xml
		books = handler.getBooks();//获取books
		for(Book book : books)//输出
		{
			System.out.println("ID: " + book.getId() + " Name: "+ book.getName() + " Price: " + book.getPrice());
		}
	}
}

//xml文件读取的处理类
public class SAXHandler extends DefaultHandler {
	//存放书籍
	private List<Book> books ;
	private String preElement = null;//存放之前一个Element
	private Book book = null;//存放一本书
	public SAXHandler(List<Book> books)
	{
		this.books = books;
	}
	public SAXHandler(){
	}
	
	public List<Book> getBooks()
	{
		return books;//返回list
	}
	
	@Override
	public void startDocument() throws SAXException {
		//标识文档的开始
		System.out.println("the document start");
		//创建一个list来
		books = new ArrayList<Book>();
		super.startDocument();
	}

	@Override
	public void startElement(String uri, String localName, String qName,
			Attributes attributes) throws SAXException {
		//当一个元素开始时，调用此方法
		System.out.println("start element " + qName);
		if("book".equals(qName))
		{
			book = new Book();//创建一本书
			book.setId(Integer.parseInt(attributes.getValue(0)));
		}
		preElement = qName;//获取当前元素
	}

	@Override
	public void endElement(String uri, String localName, String qName)
			throws SAXException {
	//一个元素结束时调用此方法
		System.out.println("end element " + qName);
		if("book".equals(qName))//判断当前结束的元素是不是book
		{
			books.add(book);//加入list中
			book = null;//清空
			System.out.println();//换一行
		}
		preElement = null;//将前一个元素清空
	}

	@Override
	public void characters(char[] ch, int start, int length)
			throws SAXException {
		//当为文本节点时调用此方法
		//判断上个节点是不是name
		if("name".equals(preElement)){
			if(book == null)
			{
				book = new Book();
			}
			book.setName(new String(ch,start,length));
		}
		//判断上个节点是否price
		if("price".equals(preElement)){
			if(book == null)
			{
				book = new Book();
			}
			book.setPrice(Float.parseFloat(new String(ch,start,length)));
		}

	}
	@Override
	public void endDocument() throws SAXException {
		//文档结束时调用
		System.out.println("end document !");
	}
}