/*
* Copyright 2010 the original author or authors.
*
* 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.gradle.cache;
/**
* A persistent store containing an object of type T.
*/
public interface PersistentStateCache<T> {
/**
* Fetches the value from this cache. A shared or exclusive lock is held while fetching the value, depending on implementation.
*/
T get();
/**
* Sets the value for this cache. An exclusive lock is held while setting the value.
*/
void set(T newValue);
/**
* Replaces the value for this cache.
*
* An exclusive lock is held while the update action is executing.
* The result of the update is returned.
*/
T update(UpdateAction<T> updateAction);
interface UpdateAction<T> {
T update(T oldValue);
}
/**
* Potentially replaces the value for this cache
*
* An exclusive lock is held while the update action is executing.
* The result of the update is returned.
*
* If the action returns the existing value, based on referential integrity,
* it is not written back to the store.
* That is, it is assumed that values are immutable.
* To force a write back to the store, ensure that you return a new object.
*/
T maybeUpdate(UpdateAction<T> updateAction);
}