org.objectstyle.cayenne.remote.service.HttpRemoteService Maven / Gradle / Ivy

Go to download
/* ====================================================================
 * 
 * The ObjectStyle Group Software License, version 1.1
 * ObjectStyle Group - http://objectstyle.org/
 * 
 * Copyright (c) 2002-2005, Andrei (Andrus) Adamchik and individual authors
 * of the software. 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 acknowlegement:
 *    "This product includes software developed by independent contributors
 *    and hosted on ObjectStyle Group web site (http://objectstyle.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 * 
 * 4. The names "ObjectStyle Group" and "Cayenne" must not be used to endorse
 *    or promote products derived from this software without prior written
 *    permission. For written permission, email
 *    "andrus at objectstyle dot org".
 * 
 * 5. Products derived from this software may not be called "ObjectStyle"
 *    or "Cayenne", nor may "ObjectStyle" or "Cayenne" appear in their
 *    names without prior written permission.
 * 
 * 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 OBJECTSTYLE GROUP 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 and hosted on ObjectStyle Group web site.  For more
 * information on the ObjectStyle Group, please see
 * .
 */
package org.objectstyle.cayenne.remote.service;

import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpSession;

import org.apache.log4j.Logger;
import org.objectstyle.cayenne.DataChannel;
import org.objectstyle.cayenne.remote.RemoteSession;

/**
 * A {@link org.objectstyle.cayenne.remote.RemoteService} implementation that stores
 * server context information in HTTP sessions.
 * 
 * @since 1.2
 * @author Andrus Adamchik
 */
public abstract class HttpRemoteService extends BaseRemoteService {

    static final String SESSION_ATTRIBUTE = "HttpRemoteService.ServerSession";

    // keep logger non-static so that it could be garbage collected with this instance..
    private final Logger logObj = Logger.getLogger(HttpRemoteService.class);

    private Map sharedChannels = new HashMap();

    /**
     * Returns an HttpSession associated with the current request in progress.
     */
    protected abstract HttpSession getSession(boolean create);

    /**
     * Returns a ServerSession object that represents Cayenne-related state associated
     * with the current session. If ServerSession hasn't been previously saved, returns
     * null.
     */
    protected ServerSession getServerSession() {
        HttpSession httpSession = getSession(true);
        return (ServerSession) httpSession.getAttribute(SESSION_ATTRIBUTE);
    }

    /**
     * Creates a new ServerSession with a dedicated DataChannel. Returned ServerSession is
     * stored in HttpSession for future reuse.
     */
    protected ServerSession createServerSession() {

        HttpSession httpSession = getSession(true);

        DataChannel channel = createChannel();
        RemoteSession remoteSession = createRemoteSession(
                httpSession.getId(),
                null,
                false);
        ServerSession serverSession = new ServerSession(remoteSession, channel);

        httpSession.setAttribute(SESSION_ATTRIBUTE, serverSession);
        return serverSession;
    }

    /**
     * Creates a new ServerSession based on a shared DataChannel. Returned ServerSession
     * is stored in HttpSession for future reuse.
     * 
     * @param name shared session name used to lookup a shared DataChannel.
     */
    protected ServerSession createServerSession(String name) {
        if (name == null) {
            throw new IllegalArgumentException("Name is null for shared session.");
        }

        HttpSession httpSession = getSession(true);
        DataChannel channel;

        synchronized (sharedChannels) {
            channel = getSharedChannel(name);
            if (channel == null) {
                channel = createChannel();
                saveSharedChannel(name, channel);
                logObj.debug("Starting a new shared channel: " + name);
            }
            else {
                logObj.debug("Joining existing shared channel: " + name);
            }
        }

        RemoteSession remoteSession = createRemoteSession(httpSession.getId(), name, true);

        ServerSession serverSession = new ServerSession(remoteSession, channel);
        httpSession.setAttribute(SESSION_ATTRIBUTE, serverSession);
        return serverSession;
    }

    protected DataChannel getSharedChannel(String name) {
        WeakReference ref = (WeakReference) sharedChannels.get(name);
        return (ref != null) ? (DataChannel) ref.get() : null;
    }

    protected void saveSharedChannel(String name, DataChannel channel) {
        // wrap value in a WeakReference so that channels can be deallocated when all
        // sessions that reference this channel time out...
        sharedChannels.put(name, new WeakReference(channel));
    }
}