XML基础知识学习

• 相比DOM是一种更为轻量级的方案， 速度快
• 采用串行方法读取 --- 逐行读取
• 编程较为复杂
• 无法修改XML数据，只能读。

publicclass test1 {
 
/**
	 * @param args
	 * @throws ParserConfigurationException
	 * @throws IOException
	 * @throws SAXException
	 * @throws TransformerException 
	 */
publicstaticvoid main(String[] args)throwsParserConfigurationException,
SAXException,IOException,TransformerException{
//		addElement();
//		updateText();
		deleteElement();
}
 
/**删除元素
	 * @throws ParserConfigurationException
	 * @throws SAXException
	 * @throws IOException
	 * @throws TransformerException 
	 * @throws TransformerFactoryConfigurationError 
	 * @throws TransformerConfigurationException 
	 */
privatestaticvoid deleteElement()throwsParserConfigurationException,SAXException,IOException,TransformerConfigurationException,TransformerFactoryConfigurationError,TransformerException{
Document document = getDocument("dtd/books.xml");
NodeList nodeList=document.getElementsByTagName("author");
Element element=(Element) nodeList.item(0);
//通过父亲来删除子节点
		element.getParentNode().removeChild(element);
		domToFile(document);
}
 
/**添加元素
	 * @throws ParserConfigurationException
	 * @throws SAXException
	 * @throws IOException
	 * @throws TransformerFactoryConfigurationError
	 * @throws TransformerConfigurationException
	 * @throws TransformerException
	 */
privatestaticvoid addElement()throwsParserConfigurationException,
SAXException,IOException,TransformerFactoryConfigurationError,
TransformerConfigurationException,TransformerException{
Document document = getDocument("dtd/books.xml");
Element element=  document.createElement("value");
		element.setTextContent("15.6");
		document.getElementsByTagName("book").item(0).appendChild(element);
		domToFile(document);
}
//修改
publicstaticvoid updateText()throwsParserConfigurationException,SAXException,IOException,TransformerConfigurationException,TransformerFactoryConfigurationError,TransformerException{
Document document = getDocument("dtd/books.xml");
NodeList nodeList=document.getElementsByTagName("author");
Element element=(Element) nodeList.item(1);
		element.setTextContent("小红");
		domToFile(document);
}
/**因为是加载到内存，所以需要回写到xml文件中
	 * @param document
	 * @throws TransformerFactoryConfigurationError
	 * @throws TransformerConfigurationException
	 * @throws TransformerException
	 */
privatestaticvoid domToFile(Document document)
throwsTransformerFactoryConfigurationError,
TransformerConfigurationException,TransformerException{
TransformerFactory factory=TransformerFactory.newInstance();
Transformer tf=factory.newTransformer();
		tf.transform(newDOMSource(document),newStreamResult("dtd/books.xml"));
}
 
/**得到document
	 * @param file
	 * @return
	 * @throws ParserConfigurationException
	 * @throws SAXException
	 * @throws IOException
	 */
publicstaticDocument getDocument(String file)
throwsParserConfigurationException,SAXException,IOException{
// TODO Auto-generated method stub
// 解析器工厂
DocumentBuilderFactory builderFactory =DocumentBuilderFactory
.newInstance();
// 解析器
DocumentBuilder db = builderFactory.newDocumentBuilder();
Document document =(Document) db.parse(file);
return document;
}
 
}

// 1.得到sax解析器工厂
 
SAXParserFactory factory =SAXParserFactory.newInstance();
 
// 2.得到sax解析器
 
SAXParser parse = factory.newSAXParser();
 
// parse.parse("xml/books.xml", new MyHandle()); //这句话可以替换下面的三句
 
// 3.得到读取器
 
XMLReader reader = parse.getXMLReader();
 
// 4设置读取器的事件处理器
 
reader.setContentHandler(newMyHandle());
 
// 5.真正读取文件
 
reader.parse("xml/books.xml");
 
classMyHandleextendsDefaultHandler{

 
@Override
 
publicvoid startDocument()throwsSAXException{
 
System.out.println("start document");
 
}
 
 
@Override
 
publicvoid startElement(String uri,String localName,String qName,
 
Attributes attributes)throwsSAXException{
 
// qName可以得到元素名称

 
// 可以通过 attributes得到当前元素的所有属性
 
System.out.println("<"+ qName +">");
 
}
 
@Overrid
 
publicvoid characters(char[] ch,int start,int length)
 
throwsSAXException{
 
// 可以得到元素中的文本信息
 
System.out.println(newString(ch, start, length));
 
}
 
@Override
 
publicvoid endElement(String uri,String localName,String qName)
 
throwsSAXException{

System.out.println("<"+ qName +">");
}

@Override
 
publicvoid endDocument()throwsSAXException{
 
System.out.println("endDocument");
 
}