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/*
 * Copyright (c) 2003 The Visigoth Software Society. All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Visigoth Software Society (http://www.visigoths.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
 *
 * 4. Neither the name "FreeMarker", "Visigoth", nor any of the names of the 
 *    project contributors may be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "FreeMarker" or "Visigoth"
 *    nor may "FreeMarker" or "Visigoth" appear in their names
 *    without prior written permission of the Visigoth Software Society.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 VISIGOTH SOFTWARE SOCIETY OR
 * ITS 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 Visigoth Software Society. For more
 * information on the Visigoth Software Society, please see
 * http://www.visigoths.org/
 */


package freemarker.cache;

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URL;

/**
 * This is an abstract template loader that can load templates whose
 * location can be described by an URL. Subclasses only need to override
 * the {@link #getURL(String)} method. Both {@link ClassTemplateLoader} and
 * {@link WebappTemplateLoader} are (quite trivial) subclasses of this class.
 * @version $Id: URLTemplateLoader.java,v 1.14 2003/01/29 08:01:17 szegedia Exp $
 * @author Attila Szegedi
 */
public abstract class URLTemplateLoader implements TemplateLoader
{
    public Object findTemplateSource(String name)
    throws
    	IOException
    {
        URL url = getURL(name);
        return url == null ? null : new URLTemplateSource(url);
    }
    
    /**
     * Given a template name (plus potential locale decorations) retrieves
     * an URL that points the template source.
     * @param name the name of the sought template, including the locale
     * decorations.
     * @return an URL that points to the template source, or null if it can
     * determine that the template source does not exist.
     */
    protected abstract URL getURL(String name);
    
    public long getLastModified(Object templateSource)
    {
        return ((URLTemplateSource) templateSource).lastModified();
    }
    
    public Reader getReader(Object templateSource, String encoding)
    throws
        IOException
    {
        return new InputStreamReader(
                ((URLTemplateSource) templateSource).getInputStream(),
                encoding);
    }
    
    public void closeTemplateSource(Object templateSource)
    throws
    	IOException
    {
        ((URLTemplateSource) templateSource).close();
    }

    /**
     * Can be used by subclasses to canonicalize URL path prefixes.
     * @param prefix the path prefix to canonicalize
     * @return the canonicalized prefix. All backslashes are replaced with
     * forward slashes, and a trailing slash is appended if the original
     * prefix wasn't empty and didn't already end with a slash.
     */
    protected static String canonicalizePrefix(String prefix)
    {
        // make it foolproof
        prefix = prefix.replace('\\', '/');
        // ensure there's a trailing slash
        if (prefix.length() > 0 && !prefix.endsWith("/"))
        {
            prefix += "/";
        }
        return prefix;
    }
}