Source for java.nio.channels.spi.SelectorProvider

   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.Channel;
  44: import java.nio.channels.DatagramChannel;
  45: import java.nio.channels.Pipe;
  46: import java.nio.channels.ServerSocketChannel;
  47: import java.nio.channels.SocketChannel;
  48: 
  49: 
  50: /**
  51:  * @author Michael Koch
  52:  * @since 1.4
  53:  */
  54: public abstract class SelectorProvider
  55: {
  56:   private static SelectorProvider systemDefaultProvider;
  57: 
  58:   /**
  59:    * Initializes the selector provider.
  60:    *
  61:    * @exception SecurityException If a security manager has been installed and
  62:    * it denies @see RuntimePermission ("selectorProvider").
  63:    */
  64:   protected SelectorProvider()
  65:   {
  66:     SecurityManager sm = System.getSecurityManager();
  67:     if (sm != null)
  68:       sm.checkPermission(new RuntimePermission("selectorProvider"));
  69:   }
  70: 
  71:   /**
  72:    * Opens a datagram channel.
  73:    *
  74:    * @return a new datagram channel object
  75:    * 
  76:    * @exception IOException if an error occurs
  77:    */
  78:   public abstract DatagramChannel openDatagramChannel()
  79:     throws IOException;
  80: 
  81:   /**
  82:    * Opens a pipe.
  83:    *
  84:    * @return a new pipe object
  85:    * 
  86:    * @exception IOException if an error occurs
  87:    */
  88:   public abstract Pipe openPipe() throws IOException;
  89: 
  90:   /**
  91:    * Opens a selector.
  92:    *
  93:    * @return a new selector object
  94:    * 
  95:    * @exception IOException if an error occurs
  96:    */
  97:   public abstract AbstractSelector openSelector() throws IOException;
  98: 
  99:   /**
 100:    * Opens a server socket channel.
 101:    *
 102:    * @return a new server socket channel object
 103:    * 
 104:    * @exception IOException if an error occurs
 105:    */
 106:   public abstract ServerSocketChannel openServerSocketChannel()
 107:     throws IOException;
 108: 
 109:   /**
 110:    * Opens a socket channel.
 111:    *
 112:    * @return a new socket channel object
 113:    * 
 114:    * @exception IOException if an error occurs
 115:    */
 116:   public abstract SocketChannel openSocketChannel() throws IOException;
 117: 
 118:   /**
 119:    * Returns the inherited channel of the VM.
 120:    *
 121:    * @return the inherited channel of the VM
 122:    *
 123:    * @throws IOException If an I/O error occurs
 124:    * @throws SecurityException If an installed security manager denies access
 125:    *         to RuntimePermission("inheritedChannel")
 126:    *
 127:    * @since 1.5
 128:    */
 129:   public Channel inheritedChannel()
 130:     throws IOException
 131:   {
 132:     SecurityManager sm = System.getSecurityManager();
 133:     if (sm != null)
 134:       {
 135:         sm.checkPermission(new RuntimePermission("inheritedChannel"));
 136:       }
 137:     // Implementation note: The default implementation can't do much more
 138:     // than return null. If a VM can provide something more useful it should
 139:     // install its own SelectorProvider (maybe a subclass of this one) to
 140:     // return something more useful.
 141:     return null;
 142:   }
 143: 
 144:   /**
 145:    * Returns the system-wide default selector provider for this invocation
 146:    * of the Java virtual machine.
 147:    *
 148:    * @return the default seletor provider
 149:    */
 150:   public static synchronized SelectorProvider provider()
 151:   {
 152:     if (systemDefaultProvider == null)
 153:       {
 154:     String propertyValue =
 155:       System.getProperty("java.nio.channels.spi.SelectorProvider");
 156: 
 157:     if (propertyValue == null || propertyValue.equals(""))
 158:       systemDefaultProvider = new SelectorProviderImpl();
 159:     else
 160:       {
 161:         try
 162:           {
 163:         systemDefaultProvider =
 164:           (SelectorProvider) Class.forName(propertyValue)
 165:                                   .newInstance();
 166:           }
 167:         catch (Exception e)
 168:           {
 169:         System.err.println("Could not instantiate class: "
 170:                            + propertyValue);
 171:         systemDefaultProvider = new SelectorProviderImpl();
 172:           }
 173:       }
 174:       }
 175: 
 176:     return systemDefaultProvider;
 177:   }
 178: }