001 /* SelectorProvider.java
002 Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038 package java.nio.channels.spi;
039
040 import gnu.java.nio.SelectorProviderImpl;
041
042 import java.io.IOException;
043 import java.nio.channels.Channel;
044 import java.nio.channels.DatagramChannel;
045 import java.nio.channels.Pipe;
046 import java.nio.channels.ServerSocketChannel;
047 import java.nio.channels.SocketChannel;
048
049
050 /**
051 * @author Michael Koch
052 * @since 1.4
053 */
054 public 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 }