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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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
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package org.apache.cayenne.remote.service;
import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpSession;
import org.apache.cayenne.DataChannel;
import org.apache.cayenne.remote.RemoteSession;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* A {@link org.apache.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 Log logObj = LogFactory.getLog(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));
}
}