src/main/java/eu/svjatoslav/commons/file/IOHelper.java

   1 /*
   2  * Svjatoslav Commons - shared library of common functionality.
   3  * Copyright ©2012-2014, Svjatoslav Agejenko, svjatoslav@svjatoslav.eu
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of version 3 of the GNU Lesser General Public License
   7  * or later as published by the Free Software Foundation.
   8  */
   9
  10 package eu.svjatoslav.commons.file;
  11
  12 import java.io.File;
  13 import java.io.FileInputStream;
  14 import java.io.FileNotFoundException;
  15 import java.io.FileOutputStream;
  16 import java.io.IOException;
  17 import java.io.UnsupportedEncodingException;
  18
  19 public class IOHelper {
  20
  21         /**
  22          * Deletes files and directories recursively. WARNING!!! Follows symlinks!!!
  23          *
  24          * @param file
  25          *            directory to delete with entire contents.
  26          *
  27          * @throws IOException
  28          *             if filesystem error happens
  29          */
  30         public static void deleteRecursively(final File file) throws IOException {
  31                 if (file.isDirectory()) {
  32
  33                         for (final File subFile : file.listFiles())
  34                                 deleteRecursively(subFile);
  35
  36                         if (!file.delete())
  37                                 throw new FileNotFoundException("Failed to delete directory: "
  38                                                 + file);
  39
  40                         return;
  41                 }
  42
  43                 if (file.isFile())
  44                         if (!file.delete())
  45                                 throw new FileNotFoundException("Failed to delete file: "
  46                                                 + file);
  47         }
  48
  49         public static byte[] getFileContents(final File file)
  50                         throws FileNotFoundException, IOException {
  51
  52                 final byte[] result = new byte[(int) file.length()];
  53                 final FileInputStream fileInputStream = new FileInputStream(file);
  54                 fileInputStream.read(result);
  55                 fileInputStream.close();
  56                 return result;
  57         }
  58
  59         public static String getFileContentsAsString(final File file)
  60                         throws FileNotFoundException, IOException {
  61                 try {
  62                         return new String(getFileContents(file), "UTF-8");
  63                 } catch (final UnsupportedEncodingException exception) {
  64                         throw new RuntimeException(exception);
  65                 }
  66         }
  67
  68         /**
  69          * Compares new file content with old file content. If content in equal,
  70          * then leaves file as-is. If content differs, then overrides file with the
  71          * new content.
  72          *
  73          * @param file
  74          *            file to potentially overwrite
  75          * @param newContent
  76          *            new content
  77          * @return <code>true</code> if file was overwritten.
  78          *
  79          * @throws FileNotFoundException
  80          *             if file is not found.
  81          * @throws IOException
  82          *             if error happens during file IO.
  83          */
  84         public static boolean overwriteFileIfContentDiffers(final File file,
  85                         final byte[] newContent) throws FileNotFoundException, IOException {
  86
  87                 checkForEquality: {
  88                         if (file.length() == newContent.length) {
  89
  90                                 final byte[] oldContent = getFileContents(file);
  91
  92                                 for (int i = 0; i < newContent.length; i++)
  93                                         if (newContent[i] != oldContent[i])
  94                                                 break checkForEquality;
  95
  96                                 // new file content in identical to old content
  97                                 return false;
  98                         }
  99                 }
 100
 101                 // New content differs from existing. Overwrite file.
 102                 saveToFile(file, newContent);
 103                 return true;
 104         }
 105
 106         public static void saveToFile(final File file, final byte[] content)
 107                         throws IOException {
 108                 final FileOutputStream fos = new FileOutputStream(file);
 109                 fos.write(content);
 110                 fos.close();
 111         }
 112
 113 }