Coverage Report - org.apache.commons.io.output.LockableFileWriter
 
Classes in this File Line Coverage Branch Coverage Complexity
LockableFileWriter
54%
44/81
56%
9/16
1.8
 
 1  
 /*
 2  
  * Licensed to the Apache Software Foundation (ASF) under one or more
 3  
  * contributor license agreements.  See the NOTICE file distributed with
 4  
  * this work for additional information regarding copyright ownership.
 5  
  * The ASF licenses this file to You under the Apache License, Version 2.0
 6  
  * (the "License"); you may not use this file except in compliance with
 7  
  * the License.  You may obtain a copy of the License at
 8  
  *
 9  
  *      http://www.apache.org/licenses/LICENSE-2.0
 10  
  *
 11  
  * Unless required by applicable law or agreed to in writing, software
 12  
  * distributed under the License is distributed on an "AS IS" BASIS,
 13  
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 14  
  * See the License for the specific language governing permissions and
 15  
  * limitations under the License.
 16  
  */
 17  
 package org.apache.commons.io.output;
 18  
 
 19  
 import java.io.File;
 20  
 import java.io.FileOutputStream;
 21  
 import java.io.IOException;
 22  
 import java.io.OutputStream;
 23  
 import java.io.OutputStreamWriter;
 24  
 import java.io.Writer;
 25  
 import java.nio.charset.Charset;
 26  
 
 27  
 import org.apache.commons.io.Charsets;
 28  
 import org.apache.commons.io.FileUtils;
 29  
 import org.apache.commons.io.IOUtils;
 30  
 
 31  
 /**
 32  
  * FileWriter that will create and honor lock files to allow simple
 33  
  * cross thread file lock handling.
 34  
  * <p>
 35  
  * This class provides a simple alternative to <code>FileWriter</code>
 36  
  * that will use a lock file to prevent duplicate writes.
 37  
  * <p>
 38  
  * <b>N.B.</b> the lock file is deleted when {@link #close()} is called
 39  
  * - or if the main file cannot be opened initially.
 40  
  * In the (unlikely) event that the lockfile cannot be deleted,
 41  
  * this is not reported, and subsequent requests using
 42  
  * the same lockfile will fail.
 43  
  * <p>
 44  
  * By default, the file will be overwritten, but this may be changed to append.
 45  
  * The lock directory may be specified, but defaults to the system property
 46  
  * <code>java.io.tmpdir</code>.
 47  
  * The encoding may also be specified, and defaults to the platform default.
 48  
  *
 49  
  * @version $Id: LockableFileWriter.java 1686747 2015-06-21 18:44:49Z krosenvold $
 50  
  */
 51  
 public class LockableFileWriter extends Writer {
 52  
     // Cannot extend ProxyWriter, as requires writer to be
 53  
     // known when super() is called
 54  
 
 55  
     /** The extension for the lock file. */
 56  
     private static final String LCK = ".lck";
 57  
 
 58  
     /** The writer to decorate. */
 59  
     private final Writer out;
 60  
     /** The lock file. */
 61  
     private final File lockFile;
 62  
 
 63  
     /**
 64  
      * Constructs a LockableFileWriter.
 65  
      * If the file exists, it is overwritten.
 66  
      *
 67  
      * @param fileName  the file to write to, not null
 68  
      * @throws NullPointerException if the file is null
 69  
      * @throws IOException in case of an I/O error
 70  
      */
 71  
     public LockableFileWriter(final String fileName) throws IOException {
 72  1
         this(fileName, false, null);
 73  0
     }
 74  
 
 75  
     /**
 76  
      * Constructs a LockableFileWriter.
 77  
      *
 78  
      * @param fileName  file to write to, not null
 79  
      * @param append  true if content should be appended, false to overwrite
 80  
      * @throws NullPointerException if the file is null
 81  
      * @throws IOException in case of an I/O error
 82  
      */
 83  
     public LockableFileWriter(final String fileName, final boolean append) throws IOException {
 84  0
         this(fileName, append, null);
 85  0
     }
 86  
 
 87  
     /**
 88  
      * Constructs a LockableFileWriter.
 89  
      *
 90  
      * @param fileName  the file to write to, not null
 91  
      * @param append  true if content should be appended, false to overwrite
 92  
      * @param lockDir  the directory in which the lock file should be held
 93  
      * @throws NullPointerException if the file is null
 94  
      * @throws IOException in case of an I/O error
 95  
      */
 96  
     public LockableFileWriter(final String fileName, final boolean append, final String lockDir) throws IOException {
 97  1
         this(new File(fileName), append, lockDir);
 98  0
     }
 99  
 
 100  
     /**
 101  
      * Constructs a LockableFileWriter.
 102  
      * If the file exists, it is overwritten.
 103  
      *
 104  
      * @param file  the file to write to, not null
 105  
      * @throws NullPointerException if the file is null
 106  
      * @throws IOException in case of an I/O error
 107  
      */
 108  
     public LockableFileWriter(final File file) throws IOException {
 109  7
         this(file, false, null);
 110  3
     }
 111  
 
 112  
     /**
 113  
      * Constructs a LockableFileWriter.
 114  
      *
 115  
      * @param file  the file to write to, not null
 116  
      * @param append  true if content should be appended, false to overwrite
 117  
      * @throws NullPointerException if the file is null
 118  
      * @throws IOException in case of an I/O error
 119  
      */
 120  
     public LockableFileWriter(final File file, final boolean append) throws IOException {
 121  0
         this(file, append, null);
 122  0
     }
 123  
 
 124  
     /**
 125  
      * Constructs a LockableFileWriter.
 126  
      *
 127  
      * @param file  the file to write to, not null
 128  
      * @param append  true if content should be appended, false to overwrite
 129  
      * @param lockDir  the directory in which the lock file should be held
 130  
      * @throws NullPointerException if the file is null
 131  
      * @throws IOException in case of an I/O error
 132  
      * @deprecated 2.5 use {@link #LockableFileWriter(File, Charset, boolean, String)} instead
 133  
      */
 134  
     @Deprecated
 135  
     public LockableFileWriter(final File file, final boolean append, final String lockDir) throws IOException {
 136  7
         this(file, Charset.defaultCharset(), append, lockDir);
 137  3
     }
 138  
 
 139  
     /**
 140  
      * Constructs a LockableFileWriter with a file encoding.
 141  
      *
 142  
      * @param file  the file to write to, not null
 143  
      * @param encoding  the encoding to use, null means platform default
 144  
      * @throws NullPointerException if the file is null
 145  
      * @throws IOException in case of an I/O error
 146  
      * @since 2.3
 147  
      */
 148  
     public LockableFileWriter(final File file, final Charset encoding) throws IOException {
 149  0
         this(file, encoding, false, null);
 150  0
     }
 151  
 
 152  
     /**
 153  
      * Constructs a LockableFileWriter with a file encoding.
 154  
      *
 155  
      * @param file  the file to write to, not null
 156  
      * @param encoding  the encoding to use, null means platform default
 157  
      * @throws NullPointerException if the file is null
 158  
      * @throws IOException in case of an I/O error
 159  
      * @throws java.nio.charset.UnsupportedCharsetException
 160  
      *             thrown instead of {@link java.io.UnsupportedEncodingException} in version 2.2 if the encoding is not
 161  
      *             supported.
 162  
      */
 163  
     public LockableFileWriter(final File file, final String encoding) throws IOException {
 164  1
         this(file, encoding, false, null);
 165  0
     }
 166  
 
 167  
     /**
 168  
      * Constructs a LockableFileWriter with a file encoding.
 169  
      *
 170  
      * @param file  the file to write to, not null
 171  
      * @param encoding  the encoding to use, null means platform default
 172  
      * @param append  true if content should be appended, false to overwrite
 173  
      * @param lockDir  the directory in which the lock file should be held
 174  
      * @throws NullPointerException if the file is null
 175  
      * @throws IOException in case of an I/O error
 176  
      * @since 2.3
 177  
      */
 178  
     public LockableFileWriter(File file, final Charset encoding, final boolean append,
 179  
             String lockDir) throws IOException {
 180  9
         super();
 181  
         // init file to create/append
 182  9
         file = file.getAbsoluteFile();
 183  8
         if (file.getParentFile() != null) {
 184  8
             FileUtils.forceMkdir(file.getParentFile());
 185  
         }
 186  8
         if (file.isDirectory()) {
 187  1
             throw new IOException("File specified is a directory");
 188  
         }
 189  
 
 190  
         // init lock file
 191  7
         if (lockDir == null) {
 192  5
             lockDir = System.getProperty("java.io.tmpdir");
 193  
         }
 194  7
         final File lockDirFile = new File(lockDir);
 195  7
         FileUtils.forceMkdir(lockDirFile);
 196  7
         testLockDir(lockDirFile);
 197  7
         lockFile = new File(lockDirFile, file.getName() + LCK);
 198  
 
 199  
         // check if locked
 200  7
         createLock();
 201  
 
 202  
         // init wrapped writer
 203  4
         out = initWriter(file, encoding, append);
 204  4
     }
 205  
 
 206  
     /**
 207  
      * Constructs a LockableFileWriter with a file encoding.
 208  
      *
 209  
      * @param file  the file to write to, not null
 210  
      * @param encoding  the encoding to use, null means platform default
 211  
      * @param append  true if content should be appended, false to overwrite
 212  
      * @param lockDir  the directory in which the lock file should be held
 213  
      * @throws NullPointerException if the file is null
 214  
      * @throws IOException in case of an I/O error
 215  
      * @throws java.nio.charset.UnsupportedCharsetException
 216  
      *             thrown instead of {@link java.io.UnsupportedEncodingException} in version 2.2 if the encoding is not
 217  
      *             supported.
 218  
      */
 219  
     public LockableFileWriter(final File file, final String encoding, final boolean append,
 220  
             final String lockDir) throws IOException {
 221  2
         this(file, Charsets.toCharset(encoding), append, lockDir);
 222  1
     }
 223  
 
 224  
     //-----------------------------------------------------------------------
 225  
     /**
 226  
      * Tests that we can write to the lock directory.
 227  
      *
 228  
      * @param lockDir  the File representing the lock directory
 229  
      * @throws IOException if we cannot write to the lock directory
 230  
      * @throws IOException if we cannot find the lock file
 231  
      */
 232  
     private void testLockDir(final File lockDir) throws IOException {
 233  7
         if (!lockDir.exists()) {
 234  0
             throw new IOException(
 235  
                     "Could not find lockDir: " + lockDir.getAbsolutePath());
 236  
         }
 237  7
         if (!lockDir.canWrite()) {
 238  0
             throw new IOException(
 239  
                     "Could not write to lockDir: " + lockDir.getAbsolutePath());
 240  
         }
 241  7
     }
 242  
 
 243  
     /**
 244  
      * Creates the lock file.
 245  
      *
 246  
      * @throws IOException if we cannot create the file
 247  
      */
 248  
     private void createLock() throws IOException {
 249  7
         synchronized (LockableFileWriter.class) {
 250  7
             if (!lockFile.createNewFile()) {
 251  3
                 throw new IOException("Can't write file, lock " +
 252  
                         lockFile.getAbsolutePath() + " exists");
 253  
             }
 254  4
             lockFile.deleteOnExit();
 255  4
         }
 256  4
     }
 257  
 
 258  
     /**
 259  
      * Initialise the wrapped file writer.
 260  
      * Ensure that a cleanup occurs if the writer creation fails.
 261  
      *
 262  
      * @param file  the file to be accessed
 263  
      * @param encoding  the encoding to use
 264  
      * @param append  true to append
 265  
      * @return The initialised writer
 266  
      * @throws IOException if an error occurs
 267  
      */
 268  
     private Writer initWriter(final File file, final Charset encoding, final boolean append) throws IOException {
 269  4
         final boolean fileExistedAlready = file.exists();
 270  4
         OutputStream stream = null;
 271  4
         Writer writer = null;
 272  
         try {
 273  4
             stream = new FileOutputStream(file.getAbsolutePath(), append);
 274  4
             writer = new OutputStreamWriter(stream, Charsets.toCharset(encoding));
 275  0
         } catch (final IOException ex) {
 276  0
             IOUtils.closeQuietly(writer);
 277  0
             IOUtils.closeQuietly(stream);
 278  0
             FileUtils.deleteQuietly(lockFile);
 279  0
             if (fileExistedAlready == false) {
 280  0
                 FileUtils.deleteQuietly(file);
 281  
             }
 282  0
             throw ex;
 283  0
         } catch (final RuntimeException ex) {
 284  0
             IOUtils.closeQuietly(writer);
 285  0
             IOUtils.closeQuietly(stream);
 286  0
             FileUtils.deleteQuietly(lockFile);
 287  0
             if (fileExistedAlready == false) {
 288  0
                 FileUtils.deleteQuietly(file);
 289  
             }
 290  0
             throw ex;
 291  4
         }
 292  4
         return writer;
 293  
     }
 294  
 
 295  
     //-----------------------------------------------------------------------
 296  
     /**
 297  
      * Closes the file writer and deletes the lockfile (if possible).
 298  
      *
 299  
      * @throws IOException if an I/O error occurs
 300  
      */
 301  
     @Override
 302  
     public void close() throws IOException {
 303  
         try {
 304  4
             out.close();
 305  
         } finally {
 306  4
             lockFile.delete();
 307  4
         }
 308  4
     }
 309  
 
 310  
     //-----------------------------------------------------------------------
 311  
     /**
 312  
      * Write a character.
 313  
      * @param idx the character to write
 314  
      * @throws IOException if an I/O error occurs
 315  
      */
 316  
     @Override
 317  
     public void write(final int idx) throws IOException {
 318  0
         out.write(idx);
 319  0
     }
 320  
 
 321  
     /**
 322  
      * Write the characters from an array.
 323  
      * @param chr the characters to write
 324  
      * @throws IOException if an I/O error occurs
 325  
      */
 326  
     @Override
 327  
     public void write(final char[] chr) throws IOException {
 328  0
         out.write(chr);
 329  0
     }
 330  
 
 331  
     /**
 332  
      * Write the specified characters from an array.
 333  
      * @param chr the characters to write
 334  
      * @param st The start offset
 335  
      * @param end The number of characters to write
 336  
      * @throws IOException if an I/O error occurs
 337  
      */
 338  
     @Override
 339  
     public void write(final char[] chr, final int st, final int end) throws IOException {
 340  0
         out.write(chr, st, end);
 341  0
     }
 342  
 
 343  
     /**
 344  
      * Write the characters from a string.
 345  
      * @param str the string to write
 346  
      * @throws IOException if an I/O error occurs
 347  
      */
 348  
     @Override
 349  
     public void write(final String str) throws IOException {
 350  0
         out.write(str);
 351  0
     }
 352  
 
 353  
     /**
 354  
      * Write the specified characters from a string.
 355  
      * @param str the string to write
 356  
      * @param st The start offset
 357  
      * @param end The number of characters to write
 358  
      * @throws IOException if an I/O error occurs
 359  
      */
 360  
     @Override
 361  
     public void write(final String str, final int st, final int end) throws IOException {
 362  0
         out.write(str, st, end);
 363  0
     }
 364  
 
 365  
     /**
 366  
      * Flush the stream.
 367  
      * @throws IOException if an I/O error occurs
 368  
      */
 369  
     @Override
 370  
     public void flush() throws IOException {
 371  0
         out.flush();
 372  0
     }
 373  
 
 374  
 }