| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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.commons.configuration2.sync; |
| |
| /** |
| * <p> |
| * An interface controlling synchronization of configuration instances. |
| * </p> |
| * <p> |
| * Each {@code Configuration} object derived from |
| * {@link org.apache.commons.configuration2.AbstractConfiguration AbstractConfiguration} |
| * has an associated {@code Synchronizer} object. Before an operation on the |
| * configuration is performed (e.g. a property read or an update), the |
| * {@code Synchronizer} is invoked. Depending on the concrete implementation of |
| * the {@code Synchronizer} used, the configuration can be made thread-safe. |
| * </p> |
| * <p> |
| * Whether a configuration has to be thread-safe or not is a matter of a |
| * concrete use case. For instance, an application that just reads some |
| * configuration settings on startup does need a thread-safe configuration |
| * implementation. A configuration in contrast which is shared between multiple |
| * components and updated concurrently should better be thread-safe. In order to |
| * satisfy both kinds of use cases, the support for thread-safety has been |
| * extracted out of the configuration implementation and refactored into this |
| * {@code Synchronizer} interface. By assigning different {@code Synchronizer} |
| * implementations to a configuration instance, the instance's support for |
| * concurrent access can be adapted to the concrete use case. |
| * </p> |
| * <p> |
| * The methods defined by this interface are similar to a <em>read-write |
| * lock</em>. The {@code Synchronizer} is notified when read or write operations |
| * start and end. A concrete implementation can then apply a specific policy to |
| * decide when threads need to block or when access to the configuration for the |
| * desired operation is granted. |
| * </p> |
| * |
| * @version $Id$ |
| * @since 2.0 |
| */ |
| public interface Synchronizer |
| { |
| /** |
| * Notifies this {@code Synchronizer} that the current thread is going to |
| * start a read operation on the managed configuration. This call can block |
| * if a concrete implementation decides that the thread has to wait until a |
| * specific condition is fulfilled. |
| */ |
| void beginRead(); |
| |
| /** |
| * Notifies this {@code Synchronizer} that the current thread has finished |
| * its read operation. This may cause other waiting threads to be granted |
| * access to the managed configuration. |
| */ |
| void endRead(); |
| |
| /** |
| * Notifies this {@code Synchronizer} that the current thread is going to |
| * start a write operation on the managed configuration. This call may |
| * block. For instance, a concrete implementation may suspend the thread |
| * until all read operations currently active are finished, |
| */ |
| void beginWrite(); |
| |
| /** |
| * Notifies this {@code Synchronizer} that the current thread has finished |
| * its write operation. This may cause other waiting threads to be granted |
| * access to the managed configuration. |
| */ |
| void endWrite(); |
| } |