    001//  Copyright 2013 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.internal.services;
    016
    017/**
    018 * A wrapper around {@link java.util.concurrent.locks.ReentrantReadWriteLock} used to manage the lock for a session.
    019 * Once a lock is acquired, a callback is registered with the {@link org.apache.tapestry5.ioc.services.PerthreadManager}
    020 * to release the lock at the end of the request.
    021 *
    022 * @since 5.4
    023 */
    024public interface SessionLock
    025{
    026    /**
    027     * Acquires the read lock, if the shared read lock, or exclusive write lock, is not already held by this thread.
    028     */
    029    void acquireReadLock();
    030
    031    /**
    032     * Acquires the exclusive write lock; may release the (shared) read lock before acquiring the write lock;
    033     * this may block for a while. Does nothing if the write lock is already held by this thread.
    034     */
    035    void acquireWriteLock();
    036}