/*
* $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/saxpath/helpers/XPathReaderFactory.java,v 1.8 2006/02/05 21:47:42 elharo Exp $
* $Revision: 1.8 $
* $Date: 2006/02/05 21:47:42 $
*
* ====================================================================
*
* Copyright 2000-2002 bob mcwhirter & James Strachan.
* All rights reserved.
*
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of the Jaxen Project nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* ====================================================================
* This software consists of voluntary contributions made by many
* individuals on behalf of the Jaxen Project and was originally
* created by bob mcwhirter <bob@werken.com> and
* James Strachan <jstrachan@apache.org>. For more information on the
* Jaxen Project, please see <http://www.jaxen.org/>.
*
* $Id: XPathReaderFactory.java,v 1.8 2006/02/05 21:47:42 elharo Exp $
*/
package org.orbeon.jaxen.saxpath.helpers;
import org.orbeon.jaxen.saxpath.SAXPathException;
import org.orbeon.jaxen.saxpath.XPathReader;
/** Create an {@link org.orbeon.jaxen.saxpath.XPathReader} from
* either a system property, or a named class.
*
* <p>
* Similar to the SAX API, the <code>XPathReaderFactory</code>
* can create an <code>XPathReader</code> from a name of a
* class passed in directly, or by inspecting the system
* property <code>org.saxpath.driver</code>.
*
* @author bob mcwhirter (bob@werken.com)
*/
public class XPathReaderFactory
{
/** The <code>org.saxpath.driver</code> property name. */
public static final String DRIVER_PROPERTY = "org.saxpath.driver";
/** The default driver to use if none is configured. */
protected static final String DEFAULT_DRIVER = "org.orbeon.jaxen.saxpath.base.XPathReader";
private XPathReaderFactory() {}
/** Create an <code>XPathReader</code> using the value of
* the <code>org.saxpath.driver</code> system property.
*
* @return an instance of the <code>XPathReader</code> specified
* by the <code>org.saxpath.driver</code> property
*
* @throws SAXPathException if the property is not set, or if
* the class can not be instantiated for some reason,
* or if the class doesn't implement the <code>XPathReader</code>
* interface
*/
public static XPathReader createReader() throws SAXPathException
{
String className = null;
try
{
className = System.getProperty( DRIVER_PROPERTY );
}
catch (SecurityException e)
{
// we'll use the default
}
if ( className == null
||
className.length() == 0 )
{
className = DEFAULT_DRIVER;
}
return createReader( className );
}
/** Create an <code>XPathReader</code> using the passed
* in class name.
*
* @param className the name of the class that implements
* the <code>XPathReader</code> interface.
*
* @return an XPathReader
*
* @throws SAXPathException if the class cannot be
* instantiated for some reason, or if the
* class doesn't implement the <code>XPathReader</code>
* interface
*/
public static XPathReader createReader(String className) throws SAXPathException
{
Class readerClass = null;
XPathReader reader = null;
try
{
// Use the full version of Class.forName(), so as to
// work better in sandboxed environments, such as
// servlet containers and applets.
readerClass = Class.forName( className,
true,
XPathReaderFactory.class.getClassLoader() );
// Double-check that it's actually the right kind of class
// before attempting instantiation.
if ( ! XPathReader.class.isAssignableFrom( readerClass ) )
{
throw new SAXPathException( "Class [" + className
+ "] does not implement the org.orbeon.jaxen.saxpath.XPathReader interface." );
}
}
catch (ClassNotFoundException e)
{
throw new SAXPathException( e );
}
try
{
reader = (XPathReader) readerClass.newInstance();
}
catch (IllegalAccessException e)
{
throw new SAXPathException( e );
}
catch (InstantiationException e)
{
throw new SAXPathException( e );
}
if ( reader == null )
{
throw new SAXPathException( "Unable to create XPathReader" );
}
return reader;
}
}