    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
    015package org.apache.tapestry5.internal.services;
    016
    017import org.apache.tapestry5.services.ApplicationStateCreator;
    018import org.apache.tapestry5.services.ApplicationStatePersistenceStrategy;
    019import org.apache.tapestry5.services.Request;
    020import org.apache.tapestry5.services.Session;
    021
    022/**
    023 * Stores ASOs in the {@link Session}, which will be created as necessary.
    024 */
    025public 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        Session session = request.getSession(false);
    079
    080        return session != null && !session.isInvalidated() && session.getAttribute(buildKey(ssoClass)) != null;
    081    }
    082}