    001    // Copyright 2007, 2008, 2009, 2010 The Apache Software Foundation
    002    //
    003    // Licensed under the Apache License, Version 2.0 (the "License");
    004    // you may not use this file except in compliance with the License.
    005    // You may obtain a copy of the License at
    006    //
    007    //     http://www.apache.org/licenses/LICENSE-2.0
    008    //
    009    // Unless required by applicable law or agreed to in writing, software
    010    // distributed under the License is distributed on an "AS IS" BASIS,
    011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012    // See the License for the specific language governing permissions and
    013    // limitations under the License.
    014
    015    package org.apache.tapestry5.internal.services;
    016
    017    import org.apache.tapestry5.services.ApplicationStateCreator;
    018    import org.apache.tapestry5.services.ApplicationStatePersistenceStrategy;
    019    import org.apache.tapestry5.services.Request;
    020    import org.apache.tapestry5.services.Session;
    021
    022    /**
    023     * Stores ASOs in the {@link Session}, which will be created as necessary.
    024     */
    025    public class SessionApplicationStatePersistenceStrategy implements ApplicationStatePersistenceStrategy
    026    {
    027        static final String PREFIX = "sso:";
    028
    029        private final Request request;
    030
    031        public SessionApplicationStatePersistenceStrategy(Request request)
    032        {
    033            this.request = request;
    034        }
    035
    036        protected Session getSession()
    037        {
    038            return request.getSession(true);
    039        }
    040
    041        @SuppressWarnings("unchecked")
    042        public <T> T get(Class<T> ssoClass, ApplicationStateCreator<T> creator)
    043        {
    044            return (T) getOrCreate(ssoClass, creator);
    045        }
    046
    047        protected <T> Object getOrCreate(Class<T> ssoClass, ApplicationStateCreator<T> creator)
    048        {
    049            Session session = getSession();
    050
    051            String key = buildKey(ssoClass);
    052
    053            Object sso = session.getAttribute(key);
    054
    055            if (sso == null)
    056            {
    057                sso = creator.create();
    058                set(ssoClass, (T) sso);
    059            }
    060
    061            return sso;
    062        }
    063
    064        protected <T> String buildKey(Class<T> ssoClass)
    065        {
    066            return PREFIX + ssoClass.getName();
    067        }
    068
    069        public <T> void set(Class<T> ssoClass, T sso)
    070        {
    071            String key = buildKey(ssoClass);
    072
    073            getSession().setAttribute(key, sso);
    074        }
    075
    076        public <T> boolean exists(Class<T> ssoClass)
    077        {
    078            String key = buildKey(ssoClass);
    079
    080            Session session = request.getSession(false);
    081
    082            return session != null && session.getAttribute(key) != null;
    083        }
    084    }