Java tutorial
/* * Copyright (c) 2007, 2017, 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.nio.channels.spi.*; import java.net.SocketOption; import java.net.SocketAddress; import java.util.concurrent.Future; import java.io.IOException; /** * An asynchronous channel for stream-oriented listening sockets. * * <p> An asynchronous server-socket channel is created by invoking the * {@link #open open} method of this class. * A newly-created asynchronous server-socket channel is open but not yet bound. * It can be bound to a local address and configured to listen for connections * by invoking the {@link #bind(SocketAddress,int) bind} method. Once bound, * the {@link #accept(Object,CompletionHandler) accept} method * is used to initiate the accepting of connections to the channel's socket. * An attempt to invoke the {@code accept} method on an unbound channel will * cause a {@link NotYetBoundException} to be thrown. * * <p> Channels of this type are safe for use by multiple concurrent threads * though at most one accept operation can be outstanding at any time. * If a thread initiates an accept operation before a previous accept operation * has completed then an {@link AcceptPendingException} will be thrown. * * <p> Socket options are configured using the {@link #setOption(SocketOption,Object) * setOption} method. Channels of this type support the following options: * <blockquote> * <table class="striped"> * <caption style="display:none">Socket options</caption> * <thead> * <tr> * <th scope="col">Option Name</th> * <th scope="col">Description</th> * </tr> * </thead> * <tbody> * <tr> * <th scope="row"> {@link java.net.StandardSocketOptions#SO_RCVBUF SO_RCVBUF} </th> * <td> The size of the socket receive buffer </td> * </tr> * <tr> * <th scope="row"> {@link java.net.StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} </th> * <td> Re-use address </td> * </tr> * </tbody> * </table> * </blockquote> * Additional (implementation specific) options may also be supported. * * <p> <b>Usage Example:</b> * <pre> * final AsynchronousServerSocketChannel listener = * AsynchronousServerSocketChannel.open().bind(new InetSocketAddress(5000)); * * listener.accept(null, new CompletionHandler<AsynchronousSocketChannel,Void>() { * public void completed(AsynchronousSocketChannel ch, Void att) { * // accept the next connection * listener.accept(null, this); * * // handle this connection * handle(ch); * } * public void failed(Throwable exc, Void att) { * ... * } * }); * </pre> * * @since 1.7 */ public abstract class AsynchronousServerSocketChannel implements AsynchronousChannel, NetworkChannel { private final AsynchronousChannelProvider provider; /** * Initializes a new instance of this class. * * @param provider * The provider that created this channel */ protected AsynchronousServerSocketChannel(AsynchronousChannelProvider provider) { this.provider = provider; } /** * Returns the provider that created this channel. * * @return The provider that created this channel */ public final AsynchronousChannelProvider provider() { return provider; } /** * Opens an asynchronous server-socket channel. * * <p> The new channel is created by invoking the {@link * java.nio.channels.spi.AsynchronousChannelProvider#openAsynchronousServerSocketChannel * openAsynchronousServerSocketChannel} method on the {@link * java.nio.channels.spi.AsynchronousChannelProvider} object that created * the given group. If the group parameter is {@code null} then the * resulting channel is created by the system-wide default provider, and * bound to the <em>default group</em>. * * @param group * The group to which the newly constructed channel should be bound, * or {@code null} for the default group * * @return A new asynchronous server socket channel * * @throws ShutdownChannelGroupException * If the channel group is shutdown * @throws IOException * If an I/O error occurs */ public static AsynchronousServerSocketChannel open(AsynchronousChannelGroup group) throws IOException { AsynchronousChannelProvider provider = (group == null) ? AsynchronousChannelProvider.provider() : group.provider(); return provider.openAsynchronousServerSocketChannel(group); } /** * Opens an asynchronous server-socket channel. * * <p> This method returns an asynchronous server socket channel that is * bound to the <em>default group</em>. This method is equivalent to evaluating * the expression: * <blockquote><pre> * open((AsynchronousChannelGroup)null); * </pre></blockquote> * * @return A new asynchronous server socket channel * * @throws IOException * If an I/O error occurs */ public static AsynchronousServerSocketChannel open() throws IOException { return open(null); } /** * Binds the channel's socket to a local address and configures the socket to * listen for connections. * * <p> An invocation of this method is equivalent to the following: * <blockquote><pre> * bind(local, 0); * </pre></blockquote> * * @param local * The local address to bind the socket, or {@code null} to bind * to an automatically assigned socket address * * @return This channel * * @throws AlreadyBoundException {@inheritDoc} * @throws UnsupportedAddressTypeException {@inheritDoc} * @throws SecurityException {@inheritDoc} * @throws ClosedChannelException {@inheritDoc} * @throws IOException {@inheritDoc} */ public final AsynchronousServerSocketChannel bind(SocketAddress local) throws IOException { return bind(local, 0); } /** * Binds the channel's socket to a local address and configures the socket to * listen for connections. * * <p> This method is used to establish an association between the socket and * a local address. Once an association is established then the socket remains * bound until the associated channel is closed. * * <p> The {@code backlog} parameter is the maximum number of pending * connections on the socket. Its exact semantics are implementation specific. * In particular, an implementation may impose a maximum length or may choose * to ignore the parameter altogther. If the {@code backlog} parameter has * the value {@code 0}, or a negative value, then an implementation specific * default is used. * * @param local * The local address to bind the socket, or {@code null} to bind * to an automatically assigned socket address * @param backlog * The maximum number of pending connections * * @return This channel * * @throws AlreadyBoundException * If the socket is already bound * @throws UnsupportedAddressTypeException * If the type of the given address is not supported * @throws SecurityException * If a security manager has been installed and its {@link * SecurityManager#checkListen checkListen} method denies the operation * @throws ClosedChannelException * If the channel is closed * @throws IOException * If some other I/O error occurs */ public abstract AsynchronousServerSocketChannel bind(SocketAddress local, int backlog) throws IOException; /** * @throws IllegalArgumentException {@inheritDoc} * @throws ClosedChannelException {@inheritDoc} * @throws IOException {@inheritDoc} */ public abstract <T> AsynchronousServerSocketChannel setOption(SocketOption<T> name, T value) throws IOException; /** * Accepts a connection. * * <p> This method initiates an asynchronous operation to accept a * connection made to this channel's socket. The {@code handler} parameter is * a completion handler that is invoked when a connection is accepted (or * the operation fails). The result passed to the completion handler is * the {@link AsynchronousSocketChannel} to the new connection. * * <p> When a new connection is accepted then the resulting {@code * AsynchronousSocketChannel} will be bound to the same {@link * AsynchronousChannelGroup} as this channel. If the group is {@link * AsynchronousChannelGroup#isShutdown shutdown} and a connection is accepted, * then the connection is closed, and the operation completes with an {@code * IOException} and cause {@link ShutdownChannelGroupException}. * * <p> To allow for concurrent handling of new connections, the completion * handler is not invoked directly by the initiating thread when a new * connection is accepted immediately (see <a * href="AsynchronousChannelGroup.html#threading">Threading</a>). * * <p> If a security manager has been installed then it verifies that the * address and port number of the connection's remote endpoint are permitted * by the security manager's {@link SecurityManager#checkAccept checkAccept} * method. The permission check is performed with privileges that are restricted * by the calling context of this method. If the permission check fails then * the connection is closed and the operation completes with a {@link * SecurityException}. * * @param <A> * The type of the attachment * @param attachment * The object to attach to the I/O operation; can be {@code null} * @param handler * The handler for consuming the result * * @throws AcceptPendingException * If an accept operation is already in progress on this channel * @throws NotYetBoundException * If this channel's socket has not yet been bound * @throws ShutdownChannelGroupException * If the channel group has terminated */ public abstract <A> void accept(A attachment, CompletionHandler<AsynchronousSocketChannel, ? super A> handler); /** * Accepts a connection. * * <p> This method initiates an asynchronous operation to accept a * connection made to this channel's socket. The method behaves in exactly * the same manner as the {@link #accept(Object, CompletionHandler)} method * except that instead of specifying a completion handler, this method * returns a {@code Future} representing the pending result. The {@code * Future}'s {@link Future#get() get} method returns the {@link * AsynchronousSocketChannel} to the new connection on successful completion. * * @return a {@code Future} object representing the pending result * * @throws AcceptPendingException * If an accept operation is already in progress on this channel * @throws NotYetBoundException * If this channel's socket has not yet been bound */ public abstract Future<AsynchronousSocketChannel> accept(); /** * {@inheritDoc} * <p> * If there is a security manager set, its {@code checkConnect} method is * called with the local address and {@code -1} as its arguments to see * if the operation is allowed. If the operation is not allowed, * a {@code SocketAddress} representing the * {@link java.net.InetAddress#getLoopbackAddress loopback} address and the * local port of the channel's socket is returned. * * @return The {@code SocketAddress} that the socket is bound to, or the * {@code SocketAddress} representing the loopback address if * denied by the security manager, or {@code null} if the * channel's socket is not bound * * @throws ClosedChannelException {@inheritDoc} * @throws IOException {@inheritDoc} */ @Override public abstract SocketAddress getLocalAddress() throws IOException; }