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// Metawidget (licensed under LGPL)
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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 library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

package org.metawidget.config.impl;

import java.io.FileNotFoundException;
import java.io.InputStream;

import org.metawidget.config.iface.ResourceResolver;
import org.metawidget.inspector.iface.InspectorException;

/**
 * A simple ResourceResolver implementation that locates the given resource by trying,
 * in order:
 * 
 * 

 * the current Thread's context classloader, if any
 * 
the classloader that loaded SimpleResourceResolver
 * 
 * 
 * This can be useful for xxxConfig classes that want to create just-in-time
 * ResourceResolvers. This saves clients having to supply their own
 * ResourceResolvers (in cases where the xxxConfig is not created using
 * ConfigReader).
 *
 * @author Richard Kennard
 */

public class SimpleResourceResolver
	implements ResourceResolver {

	//
	// Public methods
	//

	public InputStream openResource( String resource ) {

		if ( resource == null || "".equals( resource.trim() ) ) {
			throw InspectorException.newException( new FileNotFoundException( "No resource specified" ));
		}

		// Thread's ClassLoader

		ClassLoader loaderContext = Thread.currentThread().getContextClassLoader();

		if ( loaderContext != null ) {
			InputStream stream = loaderContext.getResourceAsStream( resource );

			if ( stream != null ) {
				return stream;
			}
		}

		// Our ClassLoader

		InputStream stream = getClass().getResourceAsStream( resource );

		if ( stream != null ) {
			return stream;
		}

		throw InspectorException.newException( new FileNotFoundException( "Unable to locate " + resource + " on CLASSPATH" ));
	}
}