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}