| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.impl.io.DirFile4 |
| 4 | |
| 5 | Copyright 2004 The Apache Software Foundation or its licensors, as applicable. |
| 6 | |
| 7 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 8 | you may not use this file except in compliance with the License. |
| 9 | You may obtain a copy of the License at |
| 10 | |
| 11 | http://www.apache.org/licenses/LICENSE-2.0 |
| 12 | |
| 13 | Unless required by applicable law or agreed to in writing, software |
| 14 | distributed under the License is distributed on an "AS IS" BASIS, |
| 15 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 16 | See the License for the specific language governing permissions and |
| 17 | limitations under the License. |
| 18 | |
| 19 | */ |
| 20 | |
| 21 | package org.apache.derby.impl.io; |
| 22 | |
| 23 | import org.apache.derby.iapi.services.sanity.SanityManager; |
| 24 | import org.apache.derby.io.StorageFile; |
| 25 | import org.apache.derby.io.StorageRandomAccessFile; |
| 26 | |
| 27 | import java.io.FileNotFoundException; |
| 28 | import java.io.FileOutputStream; |
| 29 | import java.io.OutputStream; |
| 30 | import java.io.File; |
| 31 | import java.io.IOException; |
| 32 | import java.io.RandomAccessFile; |
| 33 | import java.nio.channels.FileChannel; |
| 34 | import java.nio.channels.FileLock; |
| 35 | |
| 36 | /** |
| 37 | * This class implements the StorageFile interface using features of Java 1.4 not available in earlier |
| 38 | * versions of Java. |
| 39 | */ |
| 40 | class DirFile4 extends DirFile |
| 41 | { |
| 42 | |
| 43 | private RandomAccessFile lockFileOpen; |
| 44 | private FileChannel lockFileChannel; |
| 45 | private FileLock dbLock; |
| 46 | |
| 47 | private final boolean rwsOK; |
| 48 | |
| 49 | /** |
| 50 | * Construct a DirFile from a path name. |
| 51 | * |
| 52 | * @param path The path name. |
| 53 | */ |
| 54 | DirFile4( String path, boolean rwsOK) |
| 55 | { |
| 56 | super( path); |
| 57 | this.rwsOK = rwsOK; |
| 58 | } |
| 59 | |
| 60 | /** |
| 61 | * Construct a DirFile from a directory name and a file name. |
| 62 | * |
| 63 | * @param directoryName The directory part of the path name. |
| 64 | * @param fileName The name of the file within the directory. |
| 65 | */ |
| 66 | DirFile4( String directoryName, String fileName, boolean rwsOK) |
| 67 | { |
| 68 | super( directoryName, fileName); |
| 69 | this.rwsOK = rwsOK; |
| 70 | } |
| 71 | |
| 72 | /** |
| 73 | * Construct a DirFile from a directory name and a file name. |
| 74 | * |
| 75 | * @param directoryName The directory part of the path name. |
| 76 | * @param fileName The name of the file within the directory. |
| 77 | */ |
| 78 | DirFile4( DirFile directoryName, String fileName, boolean rwsOK) |
| 79 | { |
| 80 | super( directoryName, fileName); |
| 81 | this.rwsOK = rwsOK; |
| 82 | } |
| 83 | |
| 84 | /** |
| 85 | * Get the name of the parent directory if this name includes a parent. |
| 86 | * |
| 87 | * @return An StorageFile denoting the parent directory of this StorageFile, if it has a parent, null if |
| 88 | * it does not have a parent. |
| 89 | */ |
| 90 | public StorageFile getParentDir() |
| 91 | { |
| 92 | String parent = getParent(); |
| 93 | if( parent == null) |
| 94 | return null; |
| 95 | return new DirFile4( parent, rwsOK); |
| 96 | } |
| 97 | |
| 98 | /** |
| 99 | * Creates an output stream from a file name. |
| 100 | * |
| 101 | * @param append If true then data will be appended to the end of the file, if it already exists. |
| 102 | * If false and a normal file already exists with this name the file will first be truncated |
| 103 | * to zero length. |
| 104 | * |
| 105 | * @return an output stream suitable for writing to the file. |
| 106 | * |
| 107 | * @exception FileNotFoundException if the file exists but is a directory |
| 108 | * rather than a regular file, does not exist but cannot be created, or |
| 109 | * cannot be opened for any other reason. |
| 110 | */ |
| 111 | public OutputStream getOutputStream( final boolean append) throws FileNotFoundException |
| 112 | { |
| 113 | return new FileOutputStream( (File) this, append); |
| 114 | } |
| 115 | |
| 116 | public synchronized int getExclusiveFileLock() |
| 117 | { |
| 118 | boolean validExclusiveLock = false; |
| 119 | int status; |
| 120 | |
| 121 | /* |
| 122 | ** There can be a scenario where there is some other JVM that is before jkdk1.4 |
| 123 | ** had booted the system and jdk1.4 trying to boot it, in this case we will get the |
| 124 | ** Exclusive Lock even though some other JVM has already booted the database. But |
| 125 | ** the lock is not a reliable one , so we should still throw the warning. |
| 126 | ** The Way we identify this case is if "dbex.lck" file size is differen |
| 127 | ** for pre jdk1.4 jvms and jdk1.4 or above. |
| 128 | ** Zero size "dbex.lck" file is created by a jvm i.e before jdk1.4 and |
| 129 | ** File created by jdk1.4 or above writes EXCLUSIVE_FILE_LOCK value into the file. |
| 130 | ** If we are unable to acquire the lock means other JVM that |
| 131 | ** currently booted the system is also JDK1.4 or above; |
| 132 | ** In this case we could confidently throw a exception instead of |
| 133 | ** of a warning. |
| 134 | **/ |
| 135 | |
| 136 | try |
| 137 | { |
| 138 | //create the file that us used to acquire exclusive lock if it does not exists. |
| 139 | if(createNewFile()) |
| 140 | { |
| 141 | validExclusiveLock = true; |
| 142 | } |
| 143 | else |
| 144 | { |
| 145 | if(length() > 0) |
| 146 | validExclusiveLock = true; |
| 147 | } |
| 148 | |
| 149 | //If we can acquire a reliable exclusive lock , try to get it. |
| 150 | if(validExclusiveLock) |
| 151 | { |
| 152 | lockFileOpen = new RandomAccessFile((File) this, "rw"); |
| 153 | lockFileChannel = lockFileOpen.getChannel(); |
| 154 | dbLock =lockFileChannel.tryLock(); |
| 155 | if(dbLock == null) |
| 156 | { |
| 157 | lockFileChannel.close(); |
| 158 | lockFileChannel=null; |
| 159 | lockFileOpen.close(); |
| 160 | lockFileOpen = null; |
| 161 | status = EXCLUSIVE_FILE_LOCK_NOT_AVAILABLE; |
| 162 | } |
| 163 | else |
| 164 | { |
| 165 | lockFileOpen.writeInt(EXCLUSIVE_FILE_LOCK); |
| 166 | lockFileChannel.force(true); |
| 167 | status = EXCLUSIVE_FILE_LOCK; |
| 168 | } |
| 169 | } |
| 170 | else |
| 171 | { |
| 172 | status = NO_FILE_LOCK_SUPPORT; |
| 173 | } |
| 174 | |
| 175 | }catch(IOException ioe) |
| 176 | { |
| 177 | // do nothing - it may be read only medium, who knows what the |
| 178 | // problem is |
| 179 | |
| 180 | //release all the possible resource we created in this functions. |
| 181 | releaseExclusiveFileLock(); |
| 182 | status = NO_FILE_LOCK_SUPPORT; |
| 183 | if (SanityManager.DEBUG) |
| 184 | { |
| 185 | SanityManager.THROWASSERT("Unable to Acquire Exclusive Lock on " |
| 186 | + getPath()); |
| 187 | } |
| 188 | } |
| 189 | |
| 190 | return status; |
| 191 | } // end of getExclusiveFileLock |
| 192 | |
| 193 | public synchronized void releaseExclusiveFileLock() |
| 194 | { |
| 195 | try |
| 196 | { |
| 197 | if(dbLock!=null) |
| 198 | { |
| 199 | dbLock.release(); |
| 200 | dbLock =null; |
| 201 | } |
| 202 | |
| 203 | if(lockFileChannel !=null) |
| 204 | { |
| 205 | lockFileChannel.close(); |
| 206 | lockFileChannel = null; |
| 207 | } |
| 208 | |
| 209 | if(lockFileOpen !=null) |
| 210 | { |
| 211 | lockFileOpen.close(); |
| 212 | lockFileOpen = null; |
| 213 | } |
| 214 | |
| 215 | //delete the exclusive lock file name. |
| 216 | super.releaseExclusiveFileLock(); |
| 217 | }catch (IOException ioe) |
| 218 | { |
| 219 | // do nothing - it may be read only medium, who knows what the |
| 220 | // problem is |
| 221 | } |
| 222 | } // End of releaseExclusiveFileLock |
| 223 | |
| 224 | /** |
| 225 | * Get a random access (read/write) file. |
| 226 | * |
| 227 | * @param mode "r", "rw", "rws", or "rwd". The "rws" and "rwd" modes specify |
| 228 | * that the data is to be written to persistent store, consistent with the |
| 229 | * java.io.RandomAccessFile class ("synchronized" with the persistent |
| 230 | * storage, in the file system meaning of the word "synchronized"). However |
| 231 | * the implementation is not required to implement the "rws" or "rwd" |
| 232 | * modes. The implementation may treat "rws" and "rwd" as "rw". It is up to |
| 233 | * the user of this interface to call the StorageRandomAccessFile.sync |
| 234 | * method. If the "rws" or "rwd" modes are supported and the |
| 235 | * RandomAccessFile was opened in "rws" or "rwd" mode then the |
| 236 | * implementation of StorageRandomAccessFile.sync need not do anything. |
| 237 | * |
| 238 | * @return an object that can be used for random access to the file. |
| 239 | * |
| 240 | * @exception IllegalArgumentException if the mode argument is not equal to one of "r", "rw". |
| 241 | * @exception FileNotFoundException if the file exists but is a directory rather than a regular |
| 242 | * file, or cannot be opened or created for any other reason . |
| 243 | */ |
| 244 | public StorageRandomAccessFile getRandomAccessFile( String mode) throws FileNotFoundException |
| 245 | { |
| 246 | // Assume that modes "rws" and "rwd" are not supported. |
| 247 | if(!rwsOK && "rws".equals( mode) || "rwd".equals( mode)) |
| 248 | mode = "rw"; |
| 249 | return new DirRandomAccessFile4( (File) this, mode); |
| 250 | } // end of getRandomAccessFile |
| 251 | } |