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| 1 | +/* | |
| 2 | + * Copyright (c) 2000, 2009, Oracle and/or its affiliates. All rights reserved. | |
| 3 | + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| 4 | + * | |
| 5 | + * This code is free software; you can redistribute it and/or modify it | |
| 6 | + * under the terms of the GNU General Public License version 2 only, as | |
| 7 | + * published by the Free Software Foundation. Oracle designates this | |
| 8 | + * particular file as subject to the "Classpath" exception as provided | |
| 9 | + * by Oracle in the LICENSE file that accompanied this code. | |
| 10 | + * | |
| 11 | + * This code is distributed in the hope that it will be useful, but WITHOUT | |
| 12 | + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 | + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 | + * version 2 for more details (a copy is included in the LICENSE file that | |
| 15 | + * accompanied this code). | |
| 16 | + * | |
| 17 | + * You should have received a copy of the GNU General Public License version | |
| 18 | + * 2 along with this work; if not, write to the Free Software Foundation, | |
| 19 | + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 20 | + * | |
| 21 | + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 22 | + * or visit www.oracle.com if you need additional information or have any | |
| 23 | + * questions. | |
| 24 | + */ | |
| 25 | + | |
| 26 | +package java.nio.channels.spi; | |
| 27 | + | |
| 28 | +import java.io.IOException; | |
| 29 | +import java.net.ProtocolFamily; | |
| 30 | +import java.nio.channels.*; | |
| 31 | +import java.security.AccessController; | |
| 32 | +import java.security.PrivilegedAction; | |
| 33 | +import java.util.Iterator; | |
| 34 | +import java.util.ServiceLoader; | |
| 35 | +import java.util.ServiceConfigurationError; | |
| 36 | +import sun.security.action.GetPropertyAction; | |
| 37 | + | |
| 38 | + | |
| 39 | +/** | |
| 40 | + * Service-provider class for selectors and selectable channels. | |
| 41 | + * | |
| 42 | + * <p> A selector provider is a concrete subclass of this class that has a | |
| 43 | + * zero-argument constructor and implements the abstract methods specified | |
| 44 | + * below. A given invocation of the Java virtual machine maintains a single | |
| 45 | + * system-wide default provider instance, which is returned by the {@link | |
| 46 | + * #provider() provider} method. The first invocation of that method will locate | |
| 47 | + * the default provider as specified below. | |
| 48 | + * | |
| 49 | + * <p> The system-wide default provider is used by the static <tt>open</tt> | |
| 50 | + * methods of the {@link java.nio.channels.DatagramChannel#open | |
| 51 | + * DatagramChannel}, {@link java.nio.channels.Pipe#open Pipe}, {@link | |
| 52 | + * java.nio.channels.Selector#open Selector}, {@link | |
| 53 | + * java.nio.channels.ServerSocketChannel#open ServerSocketChannel}, and {@link | |
| 54 | + * java.nio.channels.SocketChannel#open SocketChannel} classes. It is also | |
| 55 | + * used by the {@link java.lang.System#inheritedChannel System.inheritedChannel()} | |
| 56 | + * method. A program may make use of a provider other than the default provider | |
| 57 | + * by instantiating that provider and then directly invoking the <tt>open</tt> | |
| 58 | + * methods defined in this class. | |
| 59 | + * | |
| 60 | + * <p> All of the methods in this class are safe for use by multiple concurrent | |
| 61 | + * threads. </p> | |
| 62 | + * | |
| 63 | + * | |
| 64 | + * @author Mark Reinhold | |
| 65 | + * @author JSR-51 Expert Group | |
| 66 | + * @since 1.4 | |
| 67 | + */ | |
| 68 | + | |
| 69 | +public abstract class SelectorProvider { | |
| 70 | + | |
| 71 | + private static final Object lock = new Object(); | |
| 72 | + private static SelectorProvider provider = null; | |
| 73 | + | |
| 74 | + /** | |
| 75 | + * Initializes a new instance of this class. </p> | |
| 76 | + * | |
| 77 | + * @throws SecurityException | |
| 78 | + * If a security manager has been installed and it denies | |
| 79 | + * {@link RuntimePermission}<tt>("selectorProvider")</tt> | |
| 80 | + */ | |
| 81 | + protected SelectorProvider() { | |
| 82 | + SecurityManager sm = System.getSecurityManager(); | |
| 83 | + if (sm != null) | |
| 84 | + sm.checkPermission(new RuntimePermission("selectorProvider")); | |
| 85 | + } | |
| 86 | + | |
| 87 | + private static boolean loadProviderFromProperty() { | |
| 88 | + String cn = System.getProperty("java.nio.channels.spi.SelectorProvider"); | |
| 89 | + if (cn == null) | |
| 90 | + return false; | |
| 91 | + try { | |
| 92 | + Class<?> c = Class.forName(cn, true, | |
| 93 | + ClassLoader.getSystemClassLoader()); | |
| 94 | + provider = (SelectorProvider)c.newInstance(); | |
| 95 | + return true; | |
| 96 | + } catch (ClassNotFoundException x) { | |
| 97 | + throw new ServiceConfigurationError(null, x); | |
| 98 | + } catch (IllegalAccessException x) { | |
| 99 | + throw new ServiceConfigurationError(null, x); | |
| 100 | + } catch (InstantiationException x) { | |
| 101 | + throw new ServiceConfigurationError(null, x); | |
| 102 | + } catch (SecurityException x) { | |
| 103 | + throw new ServiceConfigurationError(null, x); | |
| 104 | + } | |
| 105 | + } | |
| 106 | + | |
| 107 | + private static boolean loadProviderAsService() { | |
| 108 | + | |
| 109 | + ServiceLoader<SelectorProvider> sl = | |
| 110 | + ServiceLoader.load(SelectorProvider.class, | |
| 111 | + ClassLoader.getSystemClassLoader()); | |
| 112 | + Iterator<SelectorProvider> i = sl.iterator(); | |
| 113 | + for (;;) { | |
| 114 | + try { | |
| 115 | + if (!i.hasNext()) | |
| 116 | + return false; | |
| 117 | + provider = i.next(); | |
| 118 | + return true; | |
| 119 | + } catch (ServiceConfigurationError sce) { | |
| 120 | + if (sce.getCause() instanceof SecurityException) { | |
| 121 | + // Ignore the security exception, try the next provider | |
| 122 | + continue; | |
| 123 | + } | |
| 124 | + throw sce; | |
| 125 | + } | |
| 126 | + } | |
| 127 | + } | |
| 128 | + | |
| 129 | + /** | |
| 130 | + * Returns the system-wide default selector provider for this invocation of | |
| 131 | + * the Java virtual machine. | |
| 132 | + * | |
| 133 | + * <p> The first invocation of this method locates the default provider | |
| 134 | + * object as follows: </p> | |
| 135 | + * | |
| 136 | + * <ol> | |
| 137 | + * | |
| 138 | + * <li><p> If the system property | |
| 139 | + * <tt>java.nio.channels.spi.SelectorProvider</tt> is defined then it is | |
| 140 | + * taken to be the fully-qualified name of a concrete provider class. | |
| 141 | + * The class is loaded and instantiated; if this process fails then an | |
| 142 | + * unspecified error is thrown. </p></li> | |
| 143 | + * | |
| 144 | + * <li><p> If a provider class has been installed in a jar file that is | |
| 145 | + * visible to the system class loader, and that jar file contains a | |
| 146 | + * provider-configuration file named | |
| 147 | + * <tt>java.nio.channels.spi.SelectorProvider</tt> in the resource | |
| 148 | + * directory <tt>META-INF/services</tt>, then the first class name | |
| 149 | + * specified in that file is taken. The class is loaded and | |
| 150 | + * instantiated; if this process fails then an unspecified error is | |
| 151 | + * thrown. </p></li> | |
| 152 | + * | |
| 153 | + * <li><p> Finally, if no provider has been specified by any of the above | |
| 154 | + * means then the system-default provider class is instantiated and the | |
| 155 | + * result is returned. </p></li> | |
| 156 | + * | |
| 157 | + * </ol> | |
| 158 | + * | |
| 159 | + * <p> Subsequent invocations of this method return the provider that was | |
| 160 | + * returned by the first invocation. </p> | |
| 161 | + * | |
| 162 | + * @return The system-wide default selector provider | |
| 163 | + */ | |
| 164 | + public static SelectorProvider provider() { | |
| 165 | + synchronized (lock) { | |
| 166 | + if (provider != null) | |
| 167 | + return provider; | |
| 168 | + return AccessController.doPrivileged( | |
| 169 | + new PrivilegedAction<SelectorProvider>() { | |
| 170 | + public SelectorProvider run() { | |
| 171 | + if (loadProviderFromProperty()) | |
| 172 | + return provider; | |
| 173 | + if (loadProviderAsService()) | |
| 174 | + return provider; | |
| 175 | + provider = sun.nio.ch.DefaultSelectorProvider.create(); | |
| 176 | + return provider; | |
| 177 | + } | |
| 178 | + }); | |
| 179 | + } | |
| 180 | + } | |
| 181 | + | |
| 182 | + /** | |
| 183 | + * Opens a datagram channel. </p> | |
| 184 | + * | |
| 185 | + * @return The new channel | |
| 186 | + */ | |
| 187 | + public abstract DatagramChannel openDatagramChannel() | |
| 188 | + throws IOException; | |
| 189 | + | |
| 190 | + /** | |
| 191 | + * Opens a datagram channel. | |
| 192 | + * | |
| 193 | + * @param family | |
| 194 | + * The protocol family | |
| 195 | + * | |
| 196 | + * @return A new datagram channel | |
| 197 | + * | |
| 198 | + * @throws UnsupportedOperationException | |
| 199 | + * If the specified protocol family is not supported | |
| 200 | + * @throws IOException | |
| 201 | + * If an I/O error occurs | |
| 202 | + * | |
| 203 | + * @since 1.7 | |
| 204 | + */ | |
| 205 | + public abstract DatagramChannel openDatagramChannel(ProtocolFamily family) | |
| 206 | + throws IOException; | |
| 207 | + | |
| 208 | + /** | |
| 209 | + * Opens a pipe. </p> | |
| 210 | + * | |
| 211 | + * @return The new pipe | |
| 212 | + */ | |
| 213 | + public abstract Pipe openPipe() | |
| 214 | + throws IOException; | |
| 215 | + | |
| 216 | + /** | |
| 217 | + * Opens a selector. </p> | |
| 218 | + * | |
| 219 | + * @return The new selector | |
| 220 | + */ | |
| 221 | + public abstract AbstractSelector openSelector() | |
| 222 | + throws IOException; | |
| 223 | + | |
| 224 | + /** | |
| 225 | + * Opens a server-socket channel. </p> | |
| 226 | + * | |
| 227 | + * @return The new channel | |
| 228 | + */ | |
| 229 | + public abstract ServerSocketChannel openServerSocketChannel() | |
| 230 | + throws IOException; | |
| 231 | + | |
| 232 | + /** | |
| 233 | + * Opens a socket channel. </p> | |
| 234 | + * | |
| 235 | + * @return The new channel | |
| 236 | + */ | |
| 237 | + public abstract SocketChannel openSocketChannel() | |
| 238 | + throws IOException; | |
| 239 | + | |
| 240 | + /** | |
| 241 | + * Returns the channel inherited from the entity that created this | |
| 242 | + * Java virtual machine. | |
| 243 | + * | |
| 244 | + * <p> On many operating systems a process, such as a Java virtual | |
| 245 | + * machine, can be started in a manner that allows the process to | |
| 246 | + * inherit a channel from the entity that created the process. The | |
| 247 | + * manner in which this is done is system dependent, as are the | |
| 248 | + * possible entities to which the channel may be connected. For example, | |
| 249 | + * on UNIX systems, the Internet services daemon (<i>inetd</i>) is used to | |
| 250 | + * start programs to service requests when a request arrives on an | |
| 251 | + * associated network port. In this example, the process that is started, | |
| 252 | + * inherits a channel representing a network socket. | |
| 253 | + * | |
| 254 | + * <p> In cases where the inherited channel represents a network socket | |
| 255 | + * then the {@link java.nio.channels.Channel Channel} type returned | |
| 256 | + * by this method is determined as follows: | |
| 257 | + * | |
| 258 | + * <ul> | |
| 259 | + * | |
| 260 | + * <li><p> If the inherited channel represents a stream-oriented connected | |
| 261 | + * socket then a {@link java.nio.channels.SocketChannel SocketChannel} is | |
| 262 | + * returned. The socket channel is, at least initially, in blocking | |
| 263 | + * mode, bound to a socket address, and connected to a peer. | |
| 264 | + * </p></li> | |
| 265 | + * | |
| 266 | + * <li><p> If the inherited channel represents a stream-oriented listening | |
| 267 | + * socket then a {@link java.nio.channels.ServerSocketChannel | |
| 268 | + * ServerSocketChannel} is returned. The server-socket channel is, at | |
| 269 | + * least initially, in blocking mode, and bound to a socket address. | |
| 270 | + * </p></li> | |
| 271 | + * | |
| 272 | + * <li><p> If the inherited channel is a datagram-oriented socket | |
| 273 | + * then a {@link java.nio.channels.DatagramChannel DatagramChannel} is | |
| 274 | + * returned. The datagram channel is, at least initially, in blocking | |
| 275 | + * mode, and bound to a socket address. | |
| 276 | + * </p></li> | |
| 277 | + * | |
| 278 | + * </ul> | |
| 279 | + * | |
| 280 | + * <p> In addition to the network-oriented channels described, this method | |
| 281 | + * may return other kinds of channels in the future. | |
| 282 | + * | |
| 283 | + * <p> The first invocation of this method creates the channel that is | |
| 284 | + * returned. Subsequent invocations of this method return the same | |
| 285 | + * channel. </p> | |
| 286 | + * | |
| 287 | + * @return The inherited channel, if any, otherwise <tt>null</tt>. | |
| 288 | + * | |
| 289 | + * @throws IOException | |
| 290 | + * If an I/O error occurs | |
| 291 | + * | |
| 292 | + * @throws SecurityException | |
| 293 | + * If a security manager has been installed and it denies | |
| 294 | + * {@link RuntimePermission}<tt>("inheritedChannel")</tt> | |
| 295 | + * | |
| 296 | + * @since 1.5 | |
| 297 | + */ | |
| 298 | + public Channel inheritedChannel() throws IOException { | |
| 299 | + return null; | |
| 300 | + } | |
| 301 | + | |
| 302 | +} | |