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首先，先给出一个比较基本的处理xml文件的程序。你不必细看，直接跳过即可。需要时可以返回来看。 Echo01.java import java.io.*; import org.xml.sax.*; import org.xml.sax.helpers.DefaultHandler; import javax.xml.parsers.SAXParserFactory; import javax.xml.parsers.ParserConfigurationException; import javax.xml.parsers.SAXParser; public class Echo01 extends DefaultHandler { StringBuffer textBuffer; public static void main(String argv[]) { if (argv.length != 1) { System.err.println("Usage: cmd filename"); System.exit(1); } // Use an instance of ourselves as the SAX event handler DefaultHandler handler = new Echo01(); // Use the default (non-validating) parser SAXParserFactory factory = SAXParserFactory.newInstance(); try { // Set up output stream out = new OutputStreamWriter(System.out, "UTF-8"); // Parse the input SAXParser saxParser = factory.newSAXParser(); saxParser.parse( new File(argv[0]), handler); } catch (Throwable t) { t.printStackTrace(); } System.exit(0); } static private Writer out; //=========================================================== // SAX DocumentHandler methods //=========================================================== public void startDocument() throws SAXException { emit(""); nl(); } public void endDocument() throws SAXException { try { nl(); out.flush(); } catch (IOException e) { throw new SAXException("I/O error", e); } } public void startElement(String namespaceURI, String sName, // simple name String qName, // qualified name Attributes attrs) throws SAXException { echoText(); String eName = sName; // element name if ("".equals(eName)) eName = qName; // not namespaceAware emit("<"+eName); if (attrs != null) { for (int i = 0; i < attrs.getLength(); i++) { String aName = attrs.getLocalName(i); // Attr name if ("".equals(aName)) aName = attrs.getQName(i); emit(" "); emit(aName+"=\""+attrs.getValue(i)+"\""); } } emit(">"); } public void endElement(String namespaceURI, String sName, // simple name String qName // qualified name ) throws SAXException { echoText(); String eName = sName; // element name if ("".equals(eName)) eName = qName; // not namespaceAware emit(""); } public void characters(char buf[], int offset, int len) throws SAXException { String s = new String(buf, offset, len); if (textBuffer == null) { textBuffer = new StringBuffer(s); } else { textBuffer.append(s); } } //=========================================================== // Utility Methods ... //=========================================================== // Display text accumulated in the character buffer private void echoText() throws SAXException { if (textBuffer == null) return; String s = ""+textBuffer; emit(s); textBuffer = null; } // Wrap I/O exceptions in SAX exceptions, to // suit handler signature requirements private void emit(String s) throws SAXException { try { out.write(s); out.flush(); } catch (IOException e) { throw new SAXException("I/O error", e); } } // Start a new line private void nl() throws SAXException { String lineEnd = System.getProperty("line.separator"); try { out.write(lineEnd); } catch (IOException e) { throw new SAXException("I/O error", e); } } } 从程序中可以看出，解析一个XML文件的核心语句是下面一部分： // Use an instance of ourselves as the SAX event handler DefaultHandler handler = new Echo01(); // Use the default (non-validating) parser SAXParserFactory factory = SAXParserFactory.newInstance(); try { // Set up output stream out = new OutputStreamWriter(System.out, "UTF-8"); // Parse the input SAXParser saxParser = factory.newSAXParser(); saxParser.parse( new File(argv[0]), handler); } catch (Throwable t) { t.printStackTrace(); } 先是创建一个SAXParserFactory工厂类的实例，然后通过SAXParser saxParser = factory.newSAXParser(); 这个工厂类的方法创建了一个saxParser。将xml文件（new File(argv[0])）和一个Sax Event Handler（handler）（在这个程序里面，这个Handler其实是本身这个类，这个类继承了org.xml.sax.helpers.DefaultHandler 这个类，并且在前面初始化了它：DefaultHandler handler = new Echo01(); ）传递给它，让它进行解析。 关于xml文件的解析过程中的处理全部在Handler里面实现。一般Parser接受的是DefaultHandler或者HandlerBase这两个类。 这个例子里面的类是继承DefaultHandler这个虚类的。看下图：  而DefaultHandler是实现了EntityResolver, DTDHandler, ContentHandler, ErrorHandler四个接口的虚类。分别定义了如下的方法：  不同的方法，在不同的时候被Parser调用，（这个不同的时候就是Event-based） 详细介绍：（暂略） DefualtHandler的UML图如下： |