org.apache.felix.eventadmin/src/main/java/org/apache/felix/eventadmin/impl/handler/CleanBlackList.java

/*
 *   Copyright 2005 The Apache Software Foundation
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 *
 */
package org.apache.felix.eventadmin.impl.handler;

import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import org.osgi.framework.ServiceReference;

/**
 * This class implements a <tt>BlackList</tt> that removes references to unregistered
 * services automatically.
 * 
 * @see org.apache.felix.eventadmin.impl.handler.BlackList
 * 
 * @author <a href="mailto:felix-dev@incubator.apache.org">Felix Project Team</a>
 */
public class CleanBlackList implements BlackList
{
    // This set removes stale (i.e., unregistered) references on any call to contains
    private final Set m_blackList = Collections.synchronizedSet(new HashSet()
        {
            public boolean contains(final Object object)
            {
                for (Iterator iter = super.iterator(); iter.hasNext();)
                {
                    final ServiceReference ref = (ServiceReference) iter.next();

                    if (null == ref.getBundle())
                    {
                        iter.remove();
                    }
                }

                return super.contains(object);
            }
        });

    /**
     * Add a service to this blacklist.
     * 
     * @param ref The reference of the service that is blacklisted
     * 
     * @see org.apache.felix.eventadmin.impl.handler.BlackList#add(org.osgi.framework.ServiceReference)
     */
    public void add(final ServiceReference ref)
    {
        m_blackList.add(ref);
    }

    /**
     * Lookup whether a given service is blacklisted.
     * 
     * @param ref The reference of the service
     * 
     * @return <tt>true</tt> in case that the service reference has been blacklisted, 
     *      <tt>false</tt> otherwise.
     * 
     * @see org.apache.felix.eventadmin.impl.handler.BlackList#contains(org.osgi.framework.ServiceReference)
     */
    public boolean contains(final ServiceReference ref)
    {
        return m_blackList.contains(ref);
    }

}