    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
    015package 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 */
    023public 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}