framework/src/net/sf/tapestry/engine/DefaultScriptSource.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.engine;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;

import net.sf.tapestry.ApplicationRuntimeException;
import net.sf.tapestry.IResourceResolver;
import net.sf.tapestry.IScript;
import net.sf.tapestry.IScriptSource;
import net.sf.tapestry.Tapestry;
import net.sf.tapestry.script.ScriptParser;
import net.sf.tapestry.util.xml.DocumentParseException;

/**
 *  Provides basic access to scripts available on the classpath.  Scripts are cached in
 *  memory once parsed.
 *
 *  @author Howard Lewis Ship
 *  @version $Id$
 *  @since 1.0.2
 * 
 **/

public class DefaultScriptSource implements IScriptSource
{
    private IResourceResolver _resolver;

    private Map _cache = new HashMap();

    private static final int MAP_SIZE = 17;

    public DefaultScriptSource(IResourceResolver resolver)
    {
        _resolver = resolver;
    }

    public void reset()
    {
        _cache.clear();
    }

    public IScript getScript(String resourcePath)
    {
        IScript result;

        synchronized (_cache)
        {
            result = (IScript) _cache.get(resourcePath);
        }

        if (result != null)
            return result;

        result = parse(resourcePath);

        // There's a small window if reset() is invoked on a very busy system where
        // cache could be null here.

        synchronized (_cache)
        {
            _cache.put(resourcePath, result);
        }

        return result;
    }

    private IScript parse(String resourcePath)
    {
        ScriptParser parser = new ScriptParser(_resolver);
        InputStream stream = null;

        try
        {
            URL url = _resolver.getResource(resourcePath);

            if (url == null)
                throw new ApplicationRuntimeException(
                    Tapestry.getString("DefaultScriptSource.unable-to-find-script", resourcePath));

            stream = url.openStream();

            IScript result = parser.parse(stream, resourcePath);

            stream.close();

            return result;
        }
        catch (DocumentParseException ex)
        {
            throw new ApplicationRuntimeException(
                Tapestry.getString("DefaultScriptSource.unable-to-parse-script", resourcePath),
                ex);
        }
        catch (IOException ex)
        {
            throw new ApplicationRuntimeException(
                Tapestry.getString("DefaultScriptSource.unable-to-read-script", resourcePath),
                ex);
        }
        finally
        {
            Tapestry.close(stream);
        }
    }

    public String toString()
    {
        StringBuffer buffer = new StringBuffer("DefaultScriptSource@");
        buffer.append(Integer.toHexString(hashCode()));

        buffer.append('[');

        if (_cache != null)
        {
            synchronized (_cache)
            {
                buffer.append(_cache.keySet());
            }

            buffer.append(", ");
        }

        buffer.append("]");

        return buffer.toString();
    }

}