// Copyright 2007, 2008 The Apache Software Foundation

 //

 // Licensed under the Apache License, Version 2.0 (the "License");

 // you may not use this file except in compliance with the License.

 // You may obtain a copy of the License at

 //

 //     http://www.apache.org/licenses/LICENSE-2.0

 //

 // Unless required by applicable law or agreed to in writing, software

 // distributed under the License is distributed on an "AS IS" BASIS,

 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 // See the License for the specific language governing permissions and

 // limitations under the License.

 package org.apache.tapestry5.services;

 /**

  * Used by {@link ApplicationStateManager} to manage a specific kind of Session State Object (SSO) persistence. The

  * stategy is responsible for managing SSO instances within its domain.

  *

  * @see org.apache.tapestry5.services.ApplicationStatePersistenceStrategySource

  */

 public interface ApplicationStatePersistenceStrategy

 {

     /**

      * Gets the SSO from the domain. If the ASO does not already exist, it is created and stored, then returned.

      */

     <T> T get(Class<T> ssoClass, ApplicationStateCreator<T> creator);

     /**

      * Stores a new SSO, possibly replacing the existing one.

      *

      * @param <T>

      * @param ssoClass

      * @param sso      instance to store, or null to delete existing

      */

     <T> void set(Class<T> ssoClass, T sso);

     /**

      * Returns true if the SSO already exists, false if null.

      */

     <T> boolean exists(Class<T> ssoClass);

 }