PropertiesClassLoader.java

/**
 * Copyright (C) 2009 eXo Platform SAS.
 *
 * This 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 software 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 software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.exoplatform.services.resources;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Enumeration;
import java.util.Map;
import java.util.Properties;
import java.util.TreeMap;

import org.exoplatform.commons.utils.IOUtil;
import org.exoplatform.services.log.ExoLogger;
import org.exoplatform.services.log.Log;

/**
 * A {@link ClassLoader} extension that will retrieve resources from the parent classloader. For each resource having a
 * ".properties" suffix it the classloader will try first to locate a corresponding resource using the same base name but with
 * an ".xml" suffix. If such a resource is found, it will be loaded using {@link XMLResourceBundleParser}
 *
 * @author <a href="mailto:julien.viet@exoplatform.com">Julien Viet</a>
 * @version $Revision$
 */
public class PropertiesClassLoader extends ClassLoader {

    /**
     * Logger.
     */
    private static final Log LOG = ExoLogger.getLogger(PropertiesClassLoader.class);

    /**
     * Indicates whether the resource must be encoded into UTF-8
     */
    private boolean unicode;

    public PropertiesClassLoader(ClassLoader parent) {
        this(parent, false);
    }

    public PropertiesClassLoader(ClassLoader parent, boolean unicode) {
        super(parent);
        this.unicode = unicode;
    }

    public PropertiesClassLoader() {
    }

    @Override
    public URL getResource(String name) {
        if (name.endsWith(".properties")) {
            URL url = null;
            ClassLoader parent = getParent();
            while (parent != null) {
                url = getResource(parent, name, unicode);
                if (url != null) {
                    return url;
                }
                parent = parent.getParent();
            }
            if (url == null) {
                url = getResource(this, name, unicode);
            }
            return url;
        }
        return super.getResource(name);
    }

    private static URL getResource(ClassLoader cl, String name, boolean unicode) {
        String xmlName = name.substring(0, name.length() - ".properties".length()) + ".xml";
        URL url = getResource(cl, xmlName, unicode, true);
        if (url == null) {
            url = getResource(cl, name, unicode, false);
        }
        return url;
    }

    private static URL getResource(ClassLoader cl, String name, boolean unicode, boolean xml) {
        Enumeration<URL> urls = null;
        try {
            urls = cl.getResources(name);
        } catch (Exception e) {
            LOG.error("An error occured while seeking all the resources with the name " + name, e);
            return null;
        }
        if (urls != null && urls.hasMoreElements()) {
            // At least one such resource has been found
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            URL url = null;
            Map<Object, Object> props = unicode ? new TreeMap<Object, Object>() : new Properties();
            while (urls.hasMoreElements()) {
                url = urls.nextElement();
                InputStream in = null;
                try {
                    // Load content
                    in = url.openStream();
                    if (xml) {
                        props.putAll(XMLResourceBundleParser.asProperties(in));
                    } else {
                        byte[] buf = IOUtil.getStreamContentAsBytes(in);
                        ExoResourceBundle bundle = new ExoResourceBundle(new String(buf, "UTF-8"));
                        bundle.putAll(props);
                    }
                } catch (Exception e) {
                    LOG.error("An error occured while loading the content of " + url, e);
                    return null;
                } finally {
                    if (in != null) {
                        try {
                            in.close();
                        } catch (IOException e) {
                            // Do nothing
                        }
                    }
                }
            }
            try {
                // Now serialize as binary
                if (unicode) {
                    // Encoded into UTF-8
                    for (Map.Entry<Object, Object> entry : props.entrySet()) {
                        out.write(((String) entry.getKey()).getBytes("UTF-8"));
                        out.write('=');
                        out.write(((String) entry.getValue()).getBytes("UTF-8"));
                        out.write('\n');
                    }
                } else {
                    // Properties format : encoded into ISO-8859-1 with unicode characters
                    ((Properties) props).store(out, null);
                }
                out.close();
                InputStream in = new ByteArrayInputStream(out.toByteArray());

                //
                return new URL(url, "", new InputStreamURLStreamHandler(in));
            } catch (Exception e) {
                LOG.error("An error occured while creating the content of " + url, e);
                return null;
            }
        }
        return null;
    }
}