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}