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Webservice-XML与Java（五）

news 来源：原创 2024/5/2 15:26:46

处理XML的有很多工具，比如SAX、DOM4J等，还有一种解析XML方式是stax，此为oracle公司提出基于流（stream）来处理的方式，在Java中封装成了stax，和sax很像，在webservice中一般使用基于流的工具，基于dom的或多或少的会影响一些效率。WS中还要涉及到Java对象和XML之间的转换，可以直接使用JDK提供的JAXB。类似的还有：XStream、Jackson、json-lib，这些框架提供了xml和json，json和java对象的转换，根据具体的需求可选择不同的框架。

Jaxb的用法很简单，把Java对象转换为xml叫编排，xml转换为Java对象叫反编排，实例如下：

package com.tgb.xml;

import java.io.StringReader;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;

import org.junit.Test;


public class TestJaxb {

	@Test
	public void test01(){
		try {
			JAXBContext ctx = JAXBContext.newInstance(Student.class);
			Marshaller marshaller = ctx.createMarshaller();
			Student stu = new Student(1,"这是","32",new Classroom(1,"计算机","2012"));
			marshaller.marshal(stu, System.out);
		} catch (JAXBException e) {
			e.printStackTrace();
		}
	}
	
	@Test
	public void test02(){
		try {
			String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?><student><age>32</age><classroom><grade>2012</grade><id>1</id><name>计算机</name></classroom><id>1</id><name>这是</name></student>";
			JAXBContext ctx = JAXBContext.newInstance(Student.class);
			Unmarshaller um = ctx.createUnmarshaller();
			Student stu = (Student)um.unmarshal(new StringReader(xml));
			System.out.println(stu.getName() + "," + stu.getClassroom().getName());
		} catch (JAXBException e) {
			e.printStackTrace();
		}
	}	
}

下面主要讲stax操作xml的实例，首先创建一个xml文档：

<?xml version="1.0" encoding="ISO-8859-1"?>

<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>39.95</price>
	</book>

</bookstore>

基于光标的查找：

	@Test
	public void test01(){
		XMLInputFactory factory = XMLInputFactory.newInstance();
		
		InputStream is = null;
		
		is = TestStax.class.getClassLoader().getResourceAsStream("books.xml");
		
		XMLStreamReader reader;
		try {
			reader = factory.createXMLStreamReader(is);
		
			while(reader.hasNext()){
				int type = reader.next();
				
				if(type == XMLStreamConstants.START_ELEMENT){ //起始节点
					System.out.println(reader.getName());
				}else if(type == XMLStreamConstants.CHARACTERS){ //文本节点
					System.out.println(reader.getText());
				}else if(type == XMLStreamConstants.END_ELEMENT){ //结束节点
					System.out.println("/" + reader.getName());
				}
			}
		
		} catch (XMLStreamException e) {
			e.printStackTrace();
		}finally{
			if(is != null){
				try {
					is.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
	
	@Test
	public void test02(){
		
		XMLInputFactory factory = XMLInputFactory.newInstance();
		
		InputStream is = null;
		
		is = TestStax.class.getClassLoader().getResourceAsStream("books.xml");
		
		XMLStreamReader reader;
		try {
			reader = factory.createXMLStreamReader(is);

			while(reader.hasNext()){
				int type = reader.next();
				
				if(type == XMLStreamConstants.START_ELEMENT){
					String name = reader.getName().toString();
					if("book".equals(name)){
						//读取属性名和值
						System.out.println(reader.getAttributeName(0) + ":" + reader.getAttributeValue(0));
					}
					
					//获取元素内容
					if("price".equals(name)){
						System.out.println(reader.getElementText() + "\n");
					}
				}
			}
		
		} catch (XMLStreamException e) {
			e.printStackTrace();
		}finally{
			if(is != null){
				try {
					is.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}

基于迭代模型查找：

@Test
	public void test03(){
		
		XMLInputFactory factory = XMLInputFactory.newInstance();
		
		InputStream is = null;
		
		is = TestStax.class.getClassLoader().getResourceAsStream("books.xml");
		
		try {
			//基于迭代模型的操作方式
			XMLEventReader reader = factory.createXMLEventReader(is);
			int num = 0;
			while(reader.hasNext()){
				//通过XMLEvent来获取是否是某种节点类型
				XMLEvent event = reader.nextEvent();
				if(event.isStartElement()){
					//通过event.asxxx转换节点
					String name = event.asStartElement().getName().toString();
					if("title".equals(name)){
						System.out.println(reader.getElementText() + ":");
					}					
					if("price".equals(name)){
						System.out.println(reader.getElementText() + "\n");
					}
				}
				num++;
			}
			System.out.println(num);
		} catch (XMLStreamException e) {
			e.printStackTrace();
		}finally{
			if(is != null){
				try {
					is.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}

过滤器的使用：

@Test
	public void test04(){
		
		XMLInputFactory factory = XMLInputFactory.newInstance();
		
		InputStream is = null;
		
		is = TestStax.class.getClassLoader().getResourceAsStream("books.xml");
		
		try {
			
			//基于Filter的过滤方式，可以有效的过滤不用进行操作的节点，效率高
			XMLEventReader reader = factory.createFilteredReader(factory.createXMLEventReader(is), new EventFilter() {
				
				@Override
				public boolean accept(XMLEvent event) {
					if(event.isStartElement()){
						String name = event.asStartElement().getName().toString();
						if(name.equals("title") || name.equals("price")){
							return true;
						}
					}
					return false;
				}
			});
			
			int num = 0;
			while(reader.hasNext()){
				XMLEvent event = reader.nextEvent();
				if(event.isStartElement()){
					String name = event.asStartElement().getName().toString();
					if("title".equals(name)){
						System.out.println(reader.getElementText() + ":");
					}					
					if("price".equals(name)){
						System.out.println(reader.getElementText() + "\n");
					}
				}
				num++;
			}
			System.out.println(num);
		} catch (XMLStreamException e) {
			e.printStackTrace();
		}finally{
			if(is != null){
				try {
					is.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}

XPath的使用：

@Test
	public void test05(){
		
		XMLInputFactory factory = XMLInputFactory.newInstance();
		
		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
			XPath xpath = XPathFactory.newInstance().newXPath();
			
			//第一个参数就是xpath，第二个参数就是文档
			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 e = (Element)list.item(i);
				System.out.println(e.getElementsByTagName("title").item(0).getTextContent());
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			if(is != null){
				try {
					is.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}

使用XMLStreamWriter创建xml：

@Test
	public void test06(){
		
		try {
			XMLStreamWriter xsw = XMLOutputFactory.newInstance().createXMLStreamWriter(System.out);
			xsw.writeStartDocument("utf-8", "1.0");
			xsw.writeEndDocument();
			String ns = "http://www.tgb.com";
			xsw.writeStartElement("prefix","person",ns);
			xsw.writeStartElement(ns,"id");
			xsw.writeCharacters("1");
			xsw.writeEndElement();
			xsw.writeEndElement();
			xsw.flush();
			xsw.close();
		} catch (XMLStreamException e) {
			e.printStackTrace();
		} catch (FactoryConfigurationError e) {
			e.printStackTrace();
		}
	}

使用Transformer更新节点信息：

@Test
	public void test07(){
		
		try {
			InputStream 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文档对象
			Document doc = db.parse(is);
			
			//创建xpath
			XPath xpath = XPathFactory.newInstance().newXPath();
			
			Transformer tran = TransformerFactory.newInstance().newTransformer();
			
			tran.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
			tran.setOutputProperty(OutputKeys.INDENT, "yes");
			
			//第一个参数就是xpath，第二个参数就是文档
			NodeList list = (NodeList)xpath.evaluate("//book[title='Learning XML']",doc,XPathConstants.NODESET);
			
			//获取price节点
			Element be = (Element)list.item(0);
			Element e = (Element)(be.getElementsByTagName("price").item(0));
			
			e.setTextContent("232323");
			Result result = new StreamResult(System.out);
			//修改源
			tran.transform(new DOMSource(doc), result);
			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

以上都是stax的简单应用，具体可参考JDK。