framework/src/net/sf/tapestry/DefaultResourceResolver.java

/*
 *  ====================================================================
 *  The Apache Software License, Version 1.1
 *
 *  Copyright (c) 2002 The Apache Software Foundation.  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 acknowledgment:
 *  "This product includes software developed by the
 *  Apache Software Foundation (http://www.apache.org/)."
 *  Alternately, this acknowledgment may appear in the software itself,
 *  if and wherever such third-party acknowledgments normally appear.
 *
 *  4. The names "Apache" and "Apache Software Foundation" and
 *  "Apache Tapestry" must not be used to endorse or promote products
 *  derived from this software without prior written permission. For
 *  written permission, please contact apache@apache.org.
 *
 *  5. Products derived from this software may not be called "Apache",
 *  "Apache Tapestry", nor may "Apache" appear in their name, without
 *  prior written permission of the Apache Software Foundation.
 *
 *  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 APACHE SOFTWARE FOUNDATION 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 Apache Software Foundation.  For more
 *  information on the Apache Software Foundation, please see
 *  <http://www.apache.org/>.
 */
package net.sf.tapestry;

import java.net.URL;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 *  Default implementation of {@link net.sf.tapestry.IResourceResolver} based
 *  around {@link Thread#getContextClassLoader()} (which is set by the
 *  servlet container).
 *
 *  @author Howard Lewis Ship
 *  @version $Id$
 *  @since 2.3
 * 
 **/

public class DefaultResourceResolver implements IResourceResolver
{
    private static final Log LOG = LogFactory.getLog(DefaultResourceResolver.class);

    private ClassLoader _loader;

    /**
     *  Constructs a new instance using
     *  {@link Thread#getContextClassLoader()}.
     * 
     **/
    
    public DefaultResourceResolver()
    {
        this(Thread.currentThread().getContextClassLoader());
    }

    public DefaultResourceResolver(ClassLoader loader)
    {
        _loader = loader;
    }

    public URL getResource(String name)
    {
        boolean debug = LOG.isDebugEnabled();

        if (debug)
            LOG.debug("getResource(" + name + ")");

        String stripped = removeLeadingSlash(name);

        URL result = _loader.getResource(stripped);

        if (debug)
        {
            if (result == null)
                LOG.debug("Not found.");
            else
                LOG.debug("Found as " + result);
        }

        return result;
    }

    private String removeLeadingSlash(String name)
    {
        if (name.startsWith("/"))
            return name.substring(1);

        return name;
    }

    /**
     *  Invokes {@link Class#forName(java.lang.String, boolean, java.lang.ClassLoader)}.
     *  
     *  @param name the complete class name to locate and load
     *  @return The loaded class
     *  @throws ApplicationRuntimeException if loading the class throws an exception
     *  (typically  {@link ClassNotFoundException} or a security exception)
     * 
     **/
    
    public Class findClass(String name)
    {
        try
        {
            return Class.forName(name, true, _loader);
        }
        catch (Throwable t)
        {
            throw new ApplicationRuntimeException(
                Tapestry.getString("ResourceResolver.unable-to-load-class", name, _loader, t.getMessage()),
                t);
        }
    }

    /**
     * 
     *  OGNL Support for dynamic class loading.  Simply invokes {@link #findClass(String)}.
     * 
     **/
    
    public Class classForName(String name, Map map) throws ClassNotFoundException
    {
        return findClass(name);
    }

}