/* * Copyright (c) 2000 David Flanagan.  All rights reserved. * This code is from the book Java Examples in a Nutshell, 2nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book (recommended), * visit http://www.davidflanagan.com/javaexamples2. */package com.davidflanagan.examples.xml;import javax.xml.parsers.*;                   // The JAXP packageimport org.xml.sax.*;                         // The main SAX packageimport java.io.*;/** * Parse a web.xml file using JAXP and SAX1.  Print out the names * and class names of all servlets listed in the file. *  * This class implements the HandlerBase helper class, which means * that it defines all the "callback" methods that the SAX parser will * invoke to notify the application.  In this example we override the  * methods that we require. * * This example uses full package names in places to help keep the JAXP * and SAX APIs distinct. **/public class ListServlets1 extends org.xml.sax.HandlerBase {    /** The main method sets things up for parsing */    public static void main(String[] args)	throws IOException, SAXException, ParserConfigurationException    {	// Create a JAXP "parser factory" for creating SAX parsers	javax.xml.parsers.SAXParserFactory spf=SAXParserFactory.newInstance();	// Configure the parser factory for the type of parsers we require	spf.setValidating(false);  // No validation required	// Now use the parser factory to create a SAXParser object	// Note that SAXParser is a JAXP class, not a SAX class	javax.xml.parsers.SAXParser sp = spf.newSAXParser();		// Create a SAX input source for the file argument	org.xml.sax.InputSource input=new InputSource(new FileReader(args[0]));	// Give the InputSource an absolute URL for the file, so that	// it can resolve relative URLs in a <!DOCTYPE> declaration, e.g.	input.setSystemId("file://" + new File(args[0]).getAbsolutePath());	// Create an instance of this class; it defines all the handler methods	ListServlets1 handler = new ListServlets1();	// Finally, tell the parser to parse the input and notify the handler	sp.parse(input, handler);		// Instead of using the SAXParser.parse() method, which is part of the	// JAXP API, we could also use the SAX1 API directly.  Note the	// difference between the JAXP class javax.xml.parsers.SAXParser and	// the SAX1 class org.xml.sax.Parser	//	// org.xml.sax.Parser parser = sp.getParser();  // Get the SAX parser	// parser.setDocumentHandler(handler);          // Set main handler	// parser.setErrorHandler(handler);             // Set error handler	// parser.parse(input);                         // Parse!    }    StringBuffer accumulator = new StringBuffer();  // Accumulate parsed text    String servletName;      // The name of the servlet    String servletClass;     // The class name of the servlet    String servletId;        // Value of id attribute of <servlet> tag    // When the parser encounters plain text (not XML elements), it calls    // this method, which accumulates them in a string buffer    public void characters(char[] buffer, int start, int length) {	accumulator.append(buffer, start, length);    }    // Every time the parser encounters the beginning of a new element, it    // calls this method, which resets the string buffer    public void startElement(String name, AttributeList attributes) {	accumulator.setLength(0);  // Ready to accumulate new text	// If its a servlet tag, look for id attribute	if (name.equals("servlet"))	    servletId = attributes.getValue("id");    }    // When the parser encounters the end of an element, it calls this method    public void endElement(String name) {	if (name.equals("servlet-name")) {	    // After </servlet-name>, we know the servlet name saved up	    servletName = accumulator.toString().trim();	}	else if (name.equals("servlet-class")) {	    // After </servlet-class>, we've got the class name accumulated	    servletClass = accumulator.toString().trim();	}	else if (name.equals("servlet")) {	    // Assuming the document is valid, then when we parse </servlet>,	    // we know we've got a servlet name and class name to print out	    System.out.println("Servlet " + servletName +			       ((servletId != null)?" (id="+servletId+")":"") +			       ": " + servletClass);	}    }    /** This method is called when warnings occur */    public void warning(SAXParseException exception) {	System.err.println("WARNING: line " + exception.getLineNumber() + ": "+			   exception.getMessage());    }    /** This method is called when errors occur */    public void error(SAXParseException exception) {	System.err.println("ERROR: line " + exception.getLineNumber() + ": " +			   exception.getMessage());    }    /** This method is called when non-recoverable errors occur. */    public void fatalError(SAXParseException exception) throws SAXException {	System.err.println("FATAL: line " + exception.getLineNumber() + ": " +			   exception.getMessage());	throw(exception);    }}