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 }