// XMLReaderFactory.java - factory for creating a new reader.
// Written by David Megginson, sax@megginson.com
// NO WARRANTY! This class is in the Public Domain.
// $Id: XMLReaderFactory.java,v 1.1 2000/10/02 02:43:20 sboag Exp $
package org.xml.sax.helpers;
import org.xml.sax.Parser;
import org.xml.sax.XMLReader;
import org.xml.sax.SAXException;
/**
* Factory for creating an XML reader.
*
* <blockquote>
* <em>This module, both source code and documentation, is in the
* Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
* </blockquote>
*
* <p>This class contains static methods for creating an XML reader
* from an explicit class name, or for creating an XML reader based
* on the value of the <code>org.xml.sax.driver</code> system
* property:</p>
*
* <pre>
* try {
* XMLReader myReader = XMLReaderFactory.createXMLReader();
* } catch (SAXException e) {
* System.err.println(e.getMessage());
* }
* </pre>
*
* <p>Note that these methods will not be usable in environments where
* system properties are not accessible or where the application or
* applet is not permitted to load classes dynamically.</p>
*
* <p><strong>Note to implementors:</strong> SAX implementations in specialized
* environments may replace this class with a different one optimized for the
* environment, as long as its method signatures remain the same.</p>
*
* @since SAX 2.0
* @author David Megginson,
* <a href="mailto:sax@megginson.com">sax@megginson.com</a>
* @version 2.0
* @see org.xml.sax.XMLReader
*/
final public class XMLReaderFactory
{
/**
* Private constructor.
*
* <p>This constructor prevents the class from being instantiated.</p>
*/
private XMLReaderFactory ()
{
}
/**
* Attempt to create an XML reader from a system property.
*
* <p>This method uses the value of the system property
* "org.xml.sax.driver" as the full name of a Java class
* and tries to instantiate that class as a SAX2
* XMLReader.</p>
*
* <p>Note that many Java interpreters allow system properties
* to be specified on the command line.</p>
*
* @return A new XMLReader.
* @exception org.xml.sax.SAXException If the value of the
* "org.xml.sax.driver" system property is null,
* or if the class cannot be loaded and instantiated.
* @see #createXMLReader(java.lang.String)
*/
public static XMLReader createXMLReader ()
throws SAXException
{
String className = System.getProperty("org.xml.sax.driver");
if (className == null) {
Parser parser;
try {
parser = ParserFactory.makeParser();
} catch (Exception e) {
parser = null;
}
if (parser == null) {
throw new
SAXException("System property org.xml.sax.driver not specified");
} else {
return new ParserAdapter(parser);
}
} else {
return createXMLReader(className);
}
}
/**
* Attempt to create an XML reader from a class name.
*
* <p>Given a class name, this method attempts to load
* and instantiate the class as an XML reader.</p>
*
* @return A new XML reader.
* @exception org.xml.sax.SAXException If the class cannot be
* loaded, instantiated, and cast to XMLReader.
* @see #createXMLReader()
*/
public static XMLReader createXMLReader (String className)
throws SAXException
{
try {
return (XMLReader)(Class.forName(className).newInstance());
} catch (ClassNotFoundException e1) {
throw new SAXException("SAX2 driver class " + className +
" not found", e1);
} catch (IllegalAccessException e2) {
throw new SAXException("SAX2 driver class " + className +
" found but cannot be loaded", e2);
} catch (InstantiationException e3) {
throw new SAXException("SAX2 driver class " + className +
" loaded but cannot be instantiated (no empty public constructor?)",
e3);
} catch (ClassCastException e4) {
throw new SAXException("SAX2 driver class " + className +
" does not implement XMLReader", e4);
}
}
}
// end of XMLReaderFactory.java