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 049import java.security.AccessController; 050import java.security.PrivilegedAction; 051 052/** 053 * @author Michael Koch 054 * @since 1.4 055 */ 056public abstract class SelectorProvider 057{ 058 private static SelectorProvider systemDefaultProvider; 059 060 /** 061 * Initializes the selector provider. 062 * 063 * @exception SecurityException If a security manager has been installed and 064 * it denies @see RuntimePermission ("selectorProvider"). 065 */ 066 protected SelectorProvider() 067 { 068 SecurityManager sm = System.getSecurityManager(); 069 if (sm != null) 070 sm.checkPermission(new RuntimePermission("selectorProvider")); 071 } 072 073 /** 074 * Opens a datagram channel. 075 * 076 * @return a new datagram channel object 077 * 078 * @exception IOException if an error occurs 079 */ 080 public abstract DatagramChannel openDatagramChannel() 081 throws IOException; 082 083 /** 084 * Opens a pipe. 085 * 086 * @return a new pipe object 087 * 088 * @exception IOException if an error occurs 089 */ 090 public abstract Pipe openPipe() throws IOException; 091 092 /** 093 * Opens a selector. 094 * 095 * @return a new selector object 096 * 097 * @exception IOException if an error occurs 098 */ 099 public abstract AbstractSelector openSelector() throws IOException; 100 101 /** 102 * Opens a server socket channel. 103 * 104 * @return a new server socket channel object 105 * 106 * @exception IOException if an error occurs 107 */ 108 public abstract ServerSocketChannel openServerSocketChannel() 109 throws IOException; 110 111 /** 112 * Opens a socket channel. 113 * 114 * @return a new socket channel object 115 * 116 * @exception IOException if an error occurs 117 */ 118 public abstract SocketChannel openSocketChannel() throws IOException; 119 120 /** 121 * Returns the inherited channel of the VM. 122 * 123 * @return the inherited channel of the VM 124 * 125 * @throws IOException If an I/O error occurs 126 * @throws SecurityException If an installed security manager denies access 127 * to RuntimePermission("inheritedChannel") 128 * 129 * @since 1.5 130 */ 131 public Channel inheritedChannel() 132 throws IOException 133 { 134 SecurityManager sm = System.getSecurityManager(); 135 if (sm != null) 136 { 137 sm.checkPermission(new RuntimePermission("inheritedChannel")); 138 } 139 // Implementation note: The default implementation can't do much more 140 // than return null. If a VM can provide something more useful it should 141 // install its own SelectorProvider (maybe a subclass of this one) to 142 // return something more useful. 143 return null; 144 } 145 146 /** 147 * Returns the system-wide default selector provider for this invocation 148 * of the Java virtual machine. 149 * 150 * @return the default selector provider 151 */ 152 public static synchronized SelectorProvider provider() 153 { 154 if (systemDefaultProvider == null) 155 { 156 String propertyValue = AccessController.doPrivileged(new PrivilegedAction<String> () { 157 public String run() 158 { 159 return System.getProperty("java.nio.channels.spi.SelectorProvider"); 160 } 161 }); 162 163 if (propertyValue == null || propertyValue.equals("")) 164 systemDefaultProvider = new SelectorProviderImpl(); 165 else 166 { 167 try 168 { 169 systemDefaultProvider = 170 (SelectorProvider) Class.forName(propertyValue) 171 .newInstance(); 172 } 173 catch (Exception e) 174 { 175 System.err.println("Could not instantiate class: " 176 + propertyValue); 177 systemDefaultProvider = new SelectorProviderImpl(); 178 } 179 } 180 } 181 182 return systemDefaultProvider; 183 } 184}