Java SE6新特性: XML API 与Web服务4

清单 6. 地址信息文件

　　

work contact-info Location Shanghai-shuion-333 Postal 200020 Tel fix 63262299 mobile 1581344454 Appellation Mr. Wang

　　清单 7 为这个信息文件构造一个 DOM 树，并将其作为 transformer 的输入。

　　清单 7. 构造 DOM 树　

import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerException; import javax.xml.transform.TransformerFactory; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.sax.SAXResult; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.xml.sax.SAXException; import org.xml.sax.helpers.DefaultHandler; class ContentHandler extends DefaultHandler {     @Override     public void characters(char[] ch, int start, int length) throws SAXException { String name = new String(ch, start, length);         System.out.print(name + "\t");     } } public class DOMTest {     /**     * @param args     * @throws TransformerException     */     public static void main(String[] args) {         try {             DocumentBuilderFactory documentfactory = DocumentBuilderFactory                 .newInstance();             DocumentBuilder builder = documentfactory.newDocumentBuilder();             Document document = builder.newDocument();             Element root = document.createElement("work-contact-info");             Element loca = document.createElement("Location");             loca.setTextContent("Shanghai-shuion-333");             root.appendChild(loca);             Element postal = document.createElement("Postal");             postal.setTextContent("200020");             root.appendChild(postal);             Element tel = document.createElement("Tel");             root.appendChild(tel);             Element fix = document.createElement("fix");             fix.setTextContent("63262299");             tel.appendChild(fix);             Element mobile = document.createElement("mobile");             mobile.setTextContent("1581344454");             tel.appendChild(mobile);             Element appellation = document.createElement("Appellation");             appellation.setTextContent("Mr. Wang");             root.appendChild(appellation);             document.appendChild(root);             TransformerFactory tFactory = TransformerFactory.newInstance();             Transformer transformer;             transformer = tFactory.newTransformer();             SAXResult result = new SAXResult();             ContentHandler cHandler = new ContentHandler();     result.setHandler(cHandler);             transformer.transform(new DOMSource(document), result);         } catch (Exception e) {             e.printStackTrace();         }     } }

　Java SE 6 SDK 提供了至少以上三种内置的处理 XML 文件的机制。它们分别是 Simple API for XML、Document Object Model 和 Streaming API for XML。其中 SAX 和 StAX 采用了相似的模型 —— 将 XML 文件建模为元素流，DOM 采用了树形模型。带来的结果是 SAX 和 StAX 运行时空间相对 DOM 紧凑。状态保持能力则依次 SAX -> StAX -> DOM 变强。特别值得一提的是 StAX 技术是最新引进的 XML 处理技术，它结合了 SAX 和 DOM 的优点。清单 8 给出了一个粗略度量 SAX、StAX、DOM 三个框架解析同一个 XML 文件的运行效率的代码。

　　清单 8. 度量 XML 解析框架的运行时间

　 

public class StAXTest {     public static void main(String[] args) {         final String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +     "<work-contact-info>" + "<Location>Shanghai-shuion-333</Location>" + "<Postal>200020</Postal>" + "<Tel><fix>63262299</fix>" + "<mobile>1581344454</mobile></Tel>" + "<Appellation>Mr. Wang</Appellation>" + "</work-contact-info>";         for (int i = 0; i < 10000; i++) {             StAX(xml);         }         for (int i = 0; i < 10000; i++) {             SAX(xml);         }         for (int i = 0; i < 10000; i++) {             DOM(xml);         }         long current = System.currentTimeMillis();         for (int i = 0; i < 10000; i++) {             StAX(xml);         }         current = System.currentTimeMillis() - current;         System.out.println(current);         current = System.currentTimeMillis();         for (int i = 0; i < 10000; i++) { SAX(xml);         }         current = System.currentTimeMillis() - current;         System.out.println(current);         current = System.currentTimeMillis();         for (int i = 0; i < 10000; i++) { DOM(xml);         }         current = System.currentTimeMillis() - current;             System.out.println(current);     }     private static void StAX(final String xml) {         XMLInputFactory inputFactory = XMLInputFactory.newInstance();         InputStream input;         try {             input = new ByteArrayInputStream(xml.getBytes()); XMLEventReader xmlEventReader = inputFactory                 .createXMLEventReader(input);             while (xmlEventReader.hasNext()) {                 XMLEvent event = xmlEventReader.nextEvent();                 if (event.isStartElement()) {                     StartElement startElement = event.asStartElement();                 }                 if (event.isCharacters()) {                     Characters text = event.asCharacters();                     if (!text.isWhiteSpace()) {                     }                 }             }         } catch (XMLStreamException e) {             e.printStackTrace();         }     }     private static void SAX(final String xml) {         SAXParserFactory f = SAXParserFactory.newInstance();         InputStream input;         try {             SAXParser p = f.newSAXParser();             input = new ByteArrayInputStream(xml.getBytes());             p.parse(input, new DefaultHandler());         } catch (Exception e) {             e.printStackTrace();         }     }     private static void DOM(final String xml) {         DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();         InputStream input;         try {             DocumentBuilder p = f.newDocumentBuilder();             input = new ByteArrayInputStream(xml.getBytes());             p.parse(input);         } catch (Exception e) {             e.printStackTrace();         }     } }

      得出的数据如下：

2734 4953 6516