/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008-2011, Red Hat Inc. or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.internal.util.xml;

import java.io.InputStream;
import java.io.Serializable;

import org.hibernate.internal.CoreMessageLogger;
import org.hibernate.internal.util.ConfigHelper;

import org.jboss.logging.Logger;

import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;

An EntityResolver implementation which attempts to resolve various systemId URLs to local classpath look ups

Any systemId URL beginning with http://www.hibernate.org/dtd/ is
searched for as a classpath resource in the classloader which loaded the
Hibernate classes.
Any systemId URL using classpath as the scheme (i.e. starting
with classpath:// is searched for as a classpath resource using first
the current thread context classloader and then the classloader which loaded
the Hibernate classes.


Any entity references which cannot be resolved in relation to the above
rules result in returning null, which should force the SAX reader to
handle the entity reference in its default manner.
Author:
Markus Meissner, Gavin King, Steve Ebersole, Hardy Ferentschik/**
 * An {@link EntityResolver} implementation which attempts to resolve
 * various systemId URLs to local classpath look ups<ol>
 * <li>Any systemId URL beginning with <tt>http://www.hibernate.org/dtd/</tt> is
 * searched for as a classpath resource in the classloader which loaded the
 * Hibernate classes.</li>
 * <li>Any systemId URL using <tt>classpath</tt> as the scheme (i.e. starting
 * with <tt>classpath://</tt> is searched for as a classpath resource using first
 * the current thread context classloader and then the classloader which loaded
 * the Hibernate classes.
 * </ol>
 * <p/>
 * Any entity references which cannot be resolved in relation to the above
 * rules result in returning null, which should force the SAX reader to
 * handle the entity reference in its default manner.
 *
 * @author Markus Meissner
 * @author Gavin King
 * @author Steve Ebersole
 * @author Hardy Ferentschik
 */
public class DTDEntityResolver implements EntityResolver, Serializable {

	private static final CoreMessageLogger LOG = Logger.getMessageLogger( CoreMessageLogger.class, DTDEntityResolver.class.getName() );

	private static final String HIBERNATE_NAMESPACE = "http://www.hibernate.org/dtd/";
	private static final String OLD_HIBERNATE_NAMESPACE = "http://hibernate.sourceforge.net/";
	private static final String USER_NAMESPACE = "classpath://";

	public InputSource resolveEntity(String publicId, String systemId) {
		InputSource source = null; // returning null triggers default behavior
		if ( systemId != null ) {
			LOG.debugf( "Trying to resolve system-id [%s]", systemId );
			if ( systemId.startsWith( HIBERNATE_NAMESPACE ) ) {
				LOG.debug( "Recognized hibernate namespace; attempting to resolve on classpath under org/hibernate/" );
				source = resolveOnClassPath( publicId, systemId, HIBERNATE_NAMESPACE );
			}
			else if ( systemId.startsWith( OLD_HIBERNATE_NAMESPACE ) ) {
				LOG.recognizedObsoleteHibernateNamespace( OLD_HIBERNATE_NAMESPACE, HIBERNATE_NAMESPACE );
				LOG.debug( "Attempting to resolve on classpath under org/hibernate/" );
				source = resolveOnClassPath( publicId, systemId, OLD_HIBERNATE_NAMESPACE );
			}
			else if ( systemId.startsWith( USER_NAMESPACE ) ) {
				LOG.debug( "Recognized local namespace; attempting to resolve on classpath" );
				String path = systemId.substring( USER_NAMESPACE.length() );
				InputStream stream = resolveInLocalNamespace( path );
				if ( stream == null ) {
					LOG.debugf( "Unable to locate [%s] on classpath", systemId );
				}
				else {
					LOG.debugf( "Located [%s] in classpath", systemId );
					source = new InputSource( stream );
					source.setPublicId( publicId );
					source.setSystemId( systemId );
				}
			}
		}
		return source;
	}

	private InputSource resolveOnClassPath(String publicId, String systemId, String namespace) {
		InputSource source = null;
		String path = "org/hibernate/" + systemId.substring( namespace.length() );
		InputStream dtdStream = resolveInHibernateNamespace( path );
		if ( dtdStream == null ) {
			LOG.debugf( "Unable to locate [%s] on classpath", systemId );
			if ( systemId.substring( namespace.length() ).indexOf( "2.0" ) > -1 ) {
				LOG.usingOldDtd();
			}
		}
		else {
			LOG.debugf( "Located [%s] in classpath", systemId );
			source = new InputSource( dtdStream );
			source.setPublicId( publicId );
			source.setSystemId( systemId );
		}
		return source;
	}

	protected InputStream resolveInHibernateNamespace(String path) {
		return this.getClass().getClassLoader().getResourceAsStream( path );
	}

	protected InputStream resolveInLocalNamespace(String path) {
		try {
			return ConfigHelper.getUserResourceAsStream( path );
		}
		catch ( Throwable t ) {
			return null;
		}
	}
}