org.jcurl.core.helpers.Service.java Source code

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Here is the source code for org.jcurl.core.helpers.Service.java

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/*
 * jcurl java curling software framework http://www.jcurl.org Copyright (C)
 * 2005-2009 M. Rohrmoser
 * 
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 2 of the License, or (at your option) any later
 * version.
 * 
 * This program 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 General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place, Suite 330, Boston, MA 02111-1307 USA
 */
package org.jcurl.core.helpers;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.logging.Log;
import org.jcurl.core.log.JCLoggerFactory;

/**
 * Compatible to <code>sun.misc.Service</code>.
 * 
 * @author $LastChangedBy$
 * @version $Id$
 */
public class Service {

    private static final Log log = JCLoggerFactory.getLogger(Service.class);
    private static final String META_INF_SERVICES = "META-INF/services/";
    private static final Pattern pat = Pattern.compile("\\s*([^# ]+).*");
    private static final String UTF_8 = "UTF-8";

    @SuppressWarnings("unchecked")
    public static <E> Iterable<Class<E>> providerClasses(final Class<E> clz, ClassLoader cl) {
        try {
            if (cl == null)
                cl = clz.getClassLoader();
            final Collection<Class<E>> ret = new LinkedHashSet<Class<E>>();
            // scan all
            for (final Enumeration<URL> e = cl.getResources(META_INF_SERVICES + clz.getName()); e
                    .hasMoreElements();) {
                final URL o = e.nextElement();
                final BufferedReader r = new BufferedReader(new InputStreamReader(o.openStream(), UTF_8));
                for (CharSequence line = r.readLine(); line != null; line = r.readLine()) {
                    final Matcher m = pat.matcher(line);
                    if (!m.matches())
                        continue;
                    try {
                        final Class<?> c = Class.forName(m.group(1), true, cl);
                        if (clz.isAssignableFrom(c)) {
                            final Class<E> clz_ = (Class<E>) c;
                            if (ret.contains(clz_))
                                log.warn("Duplicate class " + clz_.getName() + " in " + o.toString());
                            else
                                ret.add(clz_);
                        }
                    } catch (final ClassCastException e1) {
                        // ignore.
                    } catch (final ClassNotFoundException e1) {
                        // ignore.
                    }
                }
            }
            return ret;
        } catch (final IOException e) {
            throw new RuntimeException("Uncaught Exception", e);
        }
    }

    public static <E> Iterable<E> providerInstances(final Class<E> clz, final ClassLoader cl) {
        final Collection<E> ret = new ArrayList<E>();
        for (final Class<E> elem : providerClasses(clz, cl))
            try {
                ret.add(elem.newInstance());
            } catch (final InstantiationException e1) {
                // ignore.
            } catch (final IllegalAccessException e1) {
                // ignore.
            }
        return ret;
    }

    /** Compatible to <code>sun.misc.Service#providers</code>. */
    public static <E> Iterator<E> providers(final Class<E> clz) {
        return providers(clz, clz.getClassLoader());
    }

    /** Compatible to <code>sun.misc.Service#providers</code>. */
    public static <E> Iterator<E> providers(final Class<E> clz, final ClassLoader cl) {
        return providerInstances(clz, cl).iterator();
    }
}