    001    // Copyright 2007, 2008 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.services;
    016
    017    /**
    018     * Used by {@link ApplicationStateManager} to manage a specific kind of Session State Object (SSO) persistence. The
    019     * stategy is responsible for managing SSO instances within its domain.
    020     *
    021     * @see org.apache.tapestry5.services.ApplicationStatePersistenceStrategySource
    022     */
    023    public interface ApplicationStatePersistenceStrategy
    024    {
    025        /**
    026         * Gets the SSO from the domain. If the ASO does not already exist, it is created and stored, then returned.
    027         */
    028        <T> T get(Class<T> ssoClass, ApplicationStateCreator<T> creator);
    029
    030        /**
    031         * Stores a new SSO, possibly replacing the existing one.
    032         *
    033         * @param <T>
    034         * @param ssoClass
    035         * @param sso      instance to store, or null to delete existing
    036         */
    037        <T> void set(Class<T> ssoClass, T sso);
    038
    039        /**
    040         * Returns true if the SSO already exists, false if null.
    041         */
    042        <T> boolean exists(Class<T> ssoClass);
    043    }