Connector.java

/**
 * Copyright 2005-2014 Restlet
 * 
 * The contents of this file are subject to the terms of one of the following
 * open source licenses: Apache 2.0 or or EPL 1.0 (the "Licenses"). You can
 * select the license that you prefer but you may not use this file except in
 * compliance with one of these Licenses.
 * 
 * You can obtain a copy of the Apache 2.0 license at
 * http://www.opensource.org/licenses/apache-2.0
 * 
 * You can obtain a copy of the EPL 1.0 license at
 * http://www.opensource.org/licenses/eclipse-1.0
 * 
 * See the Licenses for the specific language governing permissions and
 * limitations under the Licenses.
 * 
 * Alternatively, you can obtain a royalty free commercial license with less
 * limitations, transferable or non-transferable, directly at
 * http://restlet.com/products/restlet-framework
 * 
 * Restlet is a registered trademark of Restlet S.A.S.
 */

package org.restlet;

import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

import org.restlet.data.Protocol;

/**
 * Restlet enabling communication between Components. "A connector is an
 * abstract mechanism that mediates communication, coordination, or cooperation
 * among components. Connectors enable communication between components by
 * transferring data elements from one interface to another without changing the
 * data." Roy T. Fielding<br>
 * <br>
 * "Encapsulate the activities of accessing resources and transferring resource
 * representations. The connectors present an abstract interface for component
 * communication, enhancing simplicity by providing a clean separation of
 * concerns and hiding the underlying implementation of resources and
 * communication mechanisms" Roy T. Fielding<br>
 * <br>
 * Concurrency note: instances of this class or its subclasses can be invoked by
 * several threads at the same time and therefore must be thread-safe. You
 * should be especially careful when storing state in member variables.
 * 
 * @see <a
 *      href="http://roy.gbiv.com/pubs/dissertation/software_arch.htm#sec_1_2_2">Source
 *      dissertation</a>
 * @see <a
 *      href="http://roy.gbiv.com/pubs/dissertation/rest_arch_style.htm#sec_5_2_2">Source
 *      dissertation</a>
 * @author Jerome Louvel
 */
public abstract class Connector extends Restlet {
    /** The list of protocols simultaneously supported. */
    private final List<Protocol> protocols;

    /**
     * Constructor.
     * 
     * @param context
     *            The context.
     */
    public Connector(Context context) {
        this(context, null);
    }

    /**
     * Constructor.
     * 
     * @param context
     *            The context.
     * @param protocols
     *            The supported protocols.
     */
    public Connector(Context context, List<Protocol> protocols) {
        super(context);

        if (protocols == null) {
            this.protocols = new CopyOnWriteArrayList<Protocol>();
        } else {
            this.protocols = new CopyOnWriteArrayList<Protocol>(protocols);
        }
    }

    /**
     * Returns the modifiable list of protocols simultaneously supported.
     * 
     * @return The protocols simultaneously supported.
     */
    public List<Protocol> getProtocols() {
        return this.protocols;
    }

    /**
     * Indicates the underlying connector helper is available.
     * 
     * @return True if the underlying connector helper is available.
     */
    public abstract boolean isAvailable();

    /**
     * Sets the list of protocols simultaneously supported. This method clears
     * the current list and adds all entries in the parameter list.
     * 
     * @param protocols
     *            A list of protocols.
     */
    public void setProtocols(List<Protocol> protocols) {
        synchronized (getProtocols()) {
            if (protocols != getProtocols()) {
                getProtocols().clear();

                if (protocols != null) {
                    getProtocols().addAll(protocols);
                }
            }
        }
    }

}