Stax处理XML三——XPath的使用和写文档、修改文档

（1）XPath的使用

前面讲了Stax处理XML的查找，有基于光标的查找，和基于迭代模型的查找。Stax也支持XPath查找。

	/**
	 * XPath的使用
	 * 查找category为WEB的bookList
	 */
	@Test
	public void test06() {
		InputStream is = null;
		try {
			is = TestStax.class.getClassLoader().getResourceAsStream("books.xml");
			//创建文档处理对象
			DocumentBuilder db = DocumentBuilderFactory.newInstance().newDocumentBuilder();
			//通过DocumentBuilder创建doc的文档对象
			Document doc = db.parse(is);
			//创建XPath对象
			XPath xpath = XPathFactory.newInstance().newXPath();
			//第一个参数是xpath，第二个参数是文档
			//查找category为WEB的bookList
			NodeList list = (NodeList)xpath.evaluate("//book[@category='WEB']",doc,XPathConstants.NODESET);
			for (int i = 0; i < list.getLength(); i++) {
				//遍历输出相应的结果
				Element el = (Element)list.item(i);
				System.out.println(el.getElementsByTagName("title").item(0).getTextContent());
			}
		} catch (ParserConfigurationException e) {
			e.printStackTrace();
		} catch (SAXException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (XPathExpressionException e) {
			e.printStackTrace();
		} finally {
			try {
				if (is != null)	is.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}	
	}

输出结果：

XQuery Kick Start
Learning XML

（2）写文档：使用XMLStreamWriter创建xml

	/**
	 * 使用XMLStreamWriter创建xml
	 */
	@Test
	public void test07() {
		try {
			XMLStreamWriter xsw = XMLOutputFactory.newInstance().createXMLStreamWriter(System.out);
			xsw.writeStartDocument("UTF-8","1.0");
			xsw.writeEndDocument();
			String ns = "http://11:dd";
			//三个参数分别是前缀、标签名、命名空间URI
			xsw.writeStartElement("ns","person",ns);
			xsw.writeStartElement(ns,"id");
			//xsw.writeStartElement("person");
			//xsw.writeStartElement("id");
			xsw.writeCharacters("1");
			xsw.writeEndElement();
			xsw.writeEndElement();
			xsw.flush();
			xsw.close();
		} catch (XMLStreamException e) {
			e.printStackTrace();
		} catch (FactoryConfigurationError e) {
			e.printStackTrace();
		}
	}

输出结果:

<?xml version="1.0" encoding="UTF-8"?><ns:person><ns:id>1</ns:id></ns:person>

去掉注释部分后的输出结果：

<?xml version="1.0" encoding="UTF-8"?><ns:person><ns:id><person><id>1</id></person>

（3）修改文档：使用Transformer更新节点信息

读取文档，修改部分，并打印出文档

	/**
	 * 使用Transformer更新节点信息
	 * 修改标题为Learning XML的书的价格为333.9
	 */
	@Test
	public void test08() {
		InputStream is = null;
		try {
			is = TestStax.class.getClassLoader().getResourceAsStream("books.xml");
			//创建文档处理对象
			DocumentBuilder db = DocumentBuilderFactory.newInstance().newDocumentBuilder();
			//通过DocumentBuilder创建doc的文档对象
			Document doc = db.parse(is);
			//创建XPath对象
			XPath xpath = XPathFactory.newInstance().newXPath();
			Transformer tran = TransformerFactory.newInstance().newTransformer();
			tran.setOutputProperty(OutputKeys.ENCODING,"UTF-8");
			//设置第一行换行
			tran.setOutputProperty(OutputKeys.INDENT,"yes");
			//第一个参数是xpath，第二个参数是文档
			NodeList list = (NodeList)xpath.evaluate("//book[title='Learning XML']",XPathConstants.NODESET);
			//获取上面所查找书的price节点，并set
			Element be = (Element)list.item(0);
			Element el = (Element)(be.getElementsByTagName("price").item(0));
			el.setTextContent("333.9");
			//通过transformer修改节点
			Result result = new StreamResult(System.out);
			tran.transform(new DOMSource(doc),result);
		} catch (ParserConfigurationException e) {
			e.printStackTrace();
		} catch (SAXException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (XPathExpressionException e) {
			e.printStackTrace();
		} catch (TransformerConfigurationException e) {
			e.printStackTrace();
		} catch (TransformerFactoryConfigurationError e) {
			e.printStackTrace();
		} catch (TransformerException e) {
			e.printStackTrace();
		} finally {
			try {
				if (is != null)	is.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

输出结果：

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<bookstore>

<book category="COOKING">
<title lang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>

<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>

<book category="WEB">
<title lang="en">XQuery Kick Start</title>
<author>James McGovern</author>
<author>Per Bothner</author>
<author>Kurt Cagle</author>
<author>James Linn</author>
<author>Vaidyanathan Nagarajan</author>
<year>2003</year>
<price>49.99</price>
</book>

<book category="WEB">
<title lang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
<price>333.9</price>
</book>

</bookstore>