001/* SelectorProvider.java
002   Copyright (C) 2002, 2003, 2004  Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package java.nio.channels.spi;
039
040import gnu.java.nio.SelectorProviderImpl;
041
042import java.io.IOException;
043import java.nio.channels.Channel;
044import java.nio.channels.DatagramChannel;
045import java.nio.channels.Pipe;
046import java.nio.channels.ServerSocketChannel;
047import java.nio.channels.SocketChannel;
048
049
050/**
051 * @author Michael Koch
052 * @since 1.4
053 */
054public abstract class SelectorProvider
055{
056  private static SelectorProvider systemDefaultProvider;
057
058  /**
059   * Initializes the selector provider.
060   *
061   * @exception SecurityException If a security manager has been installed and
062   * it denies @see RuntimePermission ("selectorProvider").
063   */
064  protected SelectorProvider()
065  {
066    SecurityManager sm = System.getSecurityManager();
067    if (sm != null)
068      sm.checkPermission(new RuntimePermission("selectorProvider"));
069  }
070
071  /**
072   * Opens a datagram channel.
073   *
074   * @return a new datagram channel object
075   *
076   * @exception IOException if an error occurs
077   */
078  public abstract DatagramChannel openDatagramChannel()
079    throws IOException;
080
081  /**
082   * Opens a pipe.
083   *
084   * @return a new pipe object
085   *
086   * @exception IOException if an error occurs
087   */
088  public abstract Pipe openPipe() throws IOException;
089
090  /**
091   * Opens a selector.
092   *
093   * @return a new selector object
094   *
095   * @exception IOException if an error occurs
096   */
097  public abstract AbstractSelector openSelector() throws IOException;
098
099  /**
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}