| /* |
| * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.nio.channels; |
| |
| import java.io.IOException; |
| import java.util.concurrent.Future; // javadoc |
| |
| /** |
| * A channel that supports asynchronous I/O operations. Asynchronous I/O |
| * operations will usually take one of two forms: |
| * |
| * <ol> |
| * <li><pre>{@link Future}<V> <em>operation</em>(<em>...</em>)</pre></li> |
| * <li><pre>void <em>operation</em>(<em>...</em> A attachment, {@link |
| * CompletionHandler}<V,? super A> handler)</pre></li> |
| * </ol> |
| * |
| * where <i>operation</i> is the name of the I/O operation (read or write for |
| * example), <i>V</i> is the result type of the I/O operation, and <i>A</i> is |
| * the type of an object attached to the I/O operation to provide context when |
| * consuming the result. The attachment is important for cases where a |
| * <em>state-less</em> {@code CompletionHandler} is used to consume the result |
| * of many I/O operations. |
| * |
| * <p> In the first form, the methods defined by the {@link Future Future} |
| * interface may be used to check if the operation has completed, wait for its |
| * completion, and to retrieve the result. In the second form, a {@link |
| * CompletionHandler} is invoked to consume the result of the I/O operation when |
| * it completes or fails. |
| * |
| * <p> A channel that implements this interface is <em>asynchronously |
| * closeable</em>: If an I/O operation is outstanding on the channel and the |
| * channel's {@link #close close} method is invoked, then the I/O operation |
| * fails with the exception {@link AsynchronousCloseException}. |
| * |
| * <p> Asynchronous channels are safe for use by multiple concurrent threads. |
| * Some channel implementations may support concurrent reading and writing, but |
| * may not allow more than one read and one write operation to be outstanding at |
| * any given time. |
| * |
| * <h2>Cancellation</h2> |
| * |
| * <p> The {@code Future} interface defines the {@link Future#cancel cancel} |
| * method to cancel execution. This causes all threads waiting on the result of |
| * the I/O operation to throw {@link java.util.concurrent.CancellationException}. |
| * Whether the underlying I/O operation can be cancelled is highly implementation |
| * specific and therefore not specified. Where cancellation leaves the channel, |
| * or the entity to which it is connected, in an inconsistent state, then the |
| * channel is put into an implementation specific <em>error state</em> that |
| * prevents further attempts to initiate I/O operations that are <i>similar</i> |
| * to the operation that was cancelled. For example, if a read operation is |
| * cancelled but the implementation cannot guarantee that bytes have not been |
| * read from the channel then it puts the channel into an error state; further |
| * attempts to initiate a {@code read} operation cause an unspecified runtime |
| * exception to be thrown. Similarly, if a write operation is cancelled but the |
| * implementation cannot guarantee that bytes have not been written to the |
| * channel then subsequent attempts to initiate a {@code write} will fail with |
| * an unspecified runtime exception. |
| * |
| * <p> Where the {@link Future#cancel cancel} method is invoked with the {@code |
| * mayInterruptIfRunning} parameter set to {@code true} then the I/O operation |
| * may be interrupted by closing the channel. In that case all threads waiting |
| * on the result of the I/O operation throw {@code CancellationException} and |
| * any other I/O operations outstanding on the channel complete with the |
| * exception {@link AsynchronousCloseException}. |
| * |
| * <p> Where the {@code cancel} method is invoked to cancel read or write |
| * operations then it is recommended that all buffers used in the I/O operations |
| * be discarded or care taken to ensure that the buffers are not accessed while |
| * the channel remains open. |
| * |
| * @since 1.7 |
| */ |
| |
| public interface AsynchronousChannel |
| extends Channel |
| { |
| /** |
| * Closes this channel. |
| * |
| * <p> Any outstanding asynchronous operations upon this channel will |
| * complete with the exception {@link AsynchronousCloseException}. After a |
| * channel is closed, further attempts to initiate asynchronous I/O |
| * operations complete immediately with cause {@link ClosedChannelException}. |
| * |
| * <p> This method otherwise behaves exactly as specified by the {@link |
| * Channel} interface. |
| * |
| * @throws IOException |
| * If an I/O error occurs |
| */ |
| @Override |
| void close() throws IOException; |
| } |