gomp-20050608-branch/libjava/classpath/java/nio/channels/spi/SelectorProvider.java

   1 /* SelectorProvider.java
   2    Copyright (C) 2002, 2003, 2004  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package java.nio.channels.spi;
  39
  40 import gnu.java.nio.SelectorProviderImpl;
  41
  42 import java.io.IOException;
  43 import java.nio.channels.DatagramChannel;
  44 import java.nio.channels.Pipe;
  45 import java.nio.channels.ServerSocketChannel;
  46 import java.nio.channels.SocketChannel;
  47
  48
  49 /**
  50  * @author Michael Koch
  51  * @since 1.4
  52  */
  53 public abstract class SelectorProvider
  54 {
  55   private static SelectorProvider systemDefaultProvider;
  56
  57   /**
  58    * Initializes the selector provider.
  59    *
  60    * @exception SecurityException If a security manager has been installed and
  61    * it denies @see RuntimePermission ("selectorProvider").
  62    */
  63   protected SelectorProvider()
  64   {
  65     SecurityManager sm = System.getSecurityManager();
  66     if (sm != null)
  67       sm.checkPermission(new RuntimePermission("selectorProvider"));
  68   }
  69
  70   /**
  71    * Opens a datagram channel.
  72    *
  73    * @return a new datagram channel object
  74    *
  75    * @exception IOException if an error occurs
  76    */
  77   public abstract DatagramChannel openDatagramChannel()
  78     throws IOException;
  79
  80   /**
  81    * Opens a pipe.
  82    *
  83    * @return a new pipe object
  84    *
  85    * @exception IOException if an error occurs
  86    */
  87   public abstract Pipe openPipe() throws IOException;
  88
  89   /**
  90    * Opens a selector.
  91    *
  92    * @return a new selector object
  93    *
  94    * @exception IOException if an error occurs
  95    */
  96   public abstract AbstractSelector openSelector() throws IOException;
  97
  98   /**
  99    * Opens a server socket channel.
 100    *
 101    * @return a new server socket channel object
 102    *
 103    * @exception IOException if an error occurs
 104    */
 105   public abstract ServerSocketChannel openServerSocketChannel()
 106     throws IOException;
 107
 108   /**
 109    * Opens a socket channel.
 110    *
 111    * @return a new socket channel object
 112    *
 113    * @exception IOException if an error occurs
 114    */
 115   public abstract SocketChannel openSocketChannel() throws IOException;
 116
 117   /**
 118    * Returns the system-wide default selector provider for this invocation
 119    * of the Java virtual machine.
 120    *
 121    * @return the default seletor provider
 122    */
 123   public static synchronized SelectorProvider provider()
 124   {
 125     if (systemDefaultProvider == null)
 126       {
 127         String propertyValue =
 128           System.getProperty("java.nio.channels.spi.SelectorProvider");
 129
 130         if (propertyValue == null || propertyValue.equals(""))
 131           systemDefaultProvider = new SelectorProviderImpl();
 132         else
 133           {
 134             try
 135               {
 136                 systemDefaultProvider =
 137                   (SelectorProvider) Class.forName(propertyValue)
 138                                           .newInstance();
 139               }
 140             catch (Exception e)
 141               {
 142                 System.err.println("Could not instantiate class: "
 143                                    + propertyValue);
 144                 systemDefaultProvider = new SelectorProviderImpl();
 145               }
 146           }
 147       }
 148
 149     return systemDefaultProvider;
 150   }
 151 }