Mega Code Archive
SAX Demo
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/*
* 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.
*/
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.AttributeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
/**
*
* 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 SAXDemo 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
SAXDemo handler = new SAXDemo();
// 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);
}
}
// Sample XML file
/*
* <?xml version="1.0" encoding="ISO-8859-1"?>
*
* <web> <s id="hello_servlet_id"> <name>hello </name> <class>Hello </class>
* </s>
*
* </web>
*
*/
]]>