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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 | } | ||