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// Metawidget
//
// This file is dual licensed under both the LGPL
// (http://www.gnu.org/licenses/lgpl-2.1.html) and the EPL
// (http://www.eclipse.org/org/documents/epl-v10.php). As a
// recipient of Metawidget, you may choose to receive it under either
// the LGPL or the EPL.
//
// Commercial licenses are also available. See http://metawidget.org
// for details.

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" ));
	}
}