Chapter 8. Tar

// Read data from the Tar file f

// The UTF-8 charset
Charset utf8 = Charset.forName("utf8");

// Create the Tar file object. Text in the Tar file is encoded in UTF-8
TarFile tf = new TarFile(f, utf8);
try
{
  // Print out the names of the child entries of the directory entry /d
  TarDirectoryEntry d = (TarDirectoryEntry) tf.get(new AbsoluteLocation("/d"));
  System.out.println("Contents of /d: " + d.getChildEntries().keySet());

  // Print out the contents of the file /d/f
  TarFileEntry df = (TarFileEntry) d.getChildEntries().get("f");
  
  // Use the EntityFS utility class Files to read the text in the file.
  System.out.println(Files.readTextFile(df, utf8));
}
finally
{
  // Close the Tar archive to release all resources associated with it.
  tf.close();
}

// Parse the Tar archive in the file f
// The contents of this Tar archive is encoded with UTF-8. Most of its metadata
// are stored in PAX variables which always are encoded in UTF-8, so if we did
// not know the archive's encoding beforehand, that would probably not matter.
TarFile tf = new TarFile(f, Charset.forName("utf8"));
try
{
  // The Tar entry for the file räksmörgås.txt (räksmörgås = shrimp sandwich)
  PaxFileEntry fe = (PaxFileEntry) tf.get(
    new AbsoluteLocation("/räksmörgås.txt"));
  
  // Print out all Pax variable names
  System.out.println("Pax variables: " + fe.getPaxVariables().keySet());
  
  // Print out the value of the ctime variable (file creation time)
  System.out.println("ctime: " + fe.getPaxVariables().get("ctime"));
}
finally
{
  // Close the Tar archive to release its associated resources
  tf.close();
}

// Extract XML and Java source files from the Tar archive in the file f to the
// target directory d. The archive is compressed using gzip.

// Use a GZipReadableFile to transparently decompress the file contents.
ReadableFile decompressedView = new GZipReadableFile(f);

TarExtractor te = new TarExtractor(decompressedView);

// Create a custom specification object
TarExtractSpecification spec = new TarExtractSpecification().
  //
  // Don't overwrite files
  setOverwriteStrategy(DontOverwriteAndLogWarning.INSTANCE).
  //
  // Only extract XML and Java source files.
  // Filter on data found in the Tar entry header. The filters used are from
  // the org.at4j.tar package and they implement EntityFS' ConvenientFilter
  // interface and the marker interface TarEntryHeaderDataFilter. Custom filters are
  // easy to implement.
  //
  // We choose to only extract files. Necessary parent directories will be
  // created automatically.
  //
  // Be sure to get the parentheses right when combining filters! 
  setFilter(
    TarFileEntryFilter.FILTER.and(
      new TarEntryNameGlobFilter("*.java").or(
      new TarEntryNameGlobFilter("*.xml")))).
  //
  // The archive is encoded using UTF-8.
  setFileNameCharset(Charset.forName("utf8"));

// Extract!
te.extract(d, spec);

// Build the Tar file "myArchive.tar" in the directory targetDir.
RandomlyAccessibleFile tarFile = Directories.newFile(targetDir, "myArchive.tar");

// Configure global Tar builder settings.
TarBuilderSettings settings = new TarBuilderSettings().
  //
  // Make files and directories owned by the user rmoore (1234), group bonds 
  // (4321).
  //
  // The settings object we create here will be combined with the default
  // default settings, which means that we only have to set the properties that
  // we want to change from the default values. 
  setDefaultFileEntrySettings(
    new TarEntrySettings().
      setOwnerUid(1234).
      setOwnerUserName("rmoore").
      setOwnerGid(4321).
      setOwnerGroupName("bonds")).
  setDefaultDirectoryEntrySettings(
    new TarEntrySettings().
      setOwnerUid(1234).
      setOwnerUserName("rmoore").
      setOwnerGid(4321).
      setOwnerGroupName("bonds")).
  //
  // Use a Tar entry strategy that will create a Posix.1-2001-compatible
  // archive
  setEntryStrategy(
    // Encode file names using UTF-8
    new PaxTarEntryStrategy(Charset.forName("utf8")));

// Create the Tar builder
TarBuilder builder = new TarBuilder(tarFile, settings);

// Add a global rule that says that script files should be executable.
builder.addRule(
  new ArchiveEntrySettingsRule<TarEntrySettings>(
    //
    // The global rule's settings
    new TarEntrySettings().
      // 
      // The code is an octal value, the same as is used with the chmod command.
      setEntityMode(UnixEntityMode.forCode(0755)),
    //
    // The global rule's filter
    new NameGlobETAF("*.sh")));

// Add all files and directories from the src directory to the /source directory
// in the archive
builder.addRecursively(src, new AbsoluteLocation("/source"));

// Add the headlines from The Times online to indicate the build date...
// Open a stream
InputStream is = new URL("http://www.timesonline.co.uk/tol/feeds/rss/topstories.xml").
  openStream();
try
{
  builder.add(is, new AbsoluteLocation("/todays_news.xml"));
}
finally
{
  is.close();
}

// Close the builder to finish writing the archive.
builder.close();

// Build the Tar file "myArchive.tar.bz2" in the directory targetDir.
// Use a BZip2WritableFile to compress the archive while it is created.
WritableFile tarFile = new BZip2WritableFile(
  Directories.newFile(targetDir, "myArchive.tar.bz2"));

// Configure global Tar builder settings.
// Use the default Tar entry strategy (GnuTarEntryStrategy).
TarBuilderSettings settings = new TarBuilderSettings().
  //
  // Files are not world readable
  setDefaultFileEntrySettings(
    new TarEntrySettings().
      setEntityMode(UnixEntityMode.forCode(0640)));

// Create the Tar builder
TarStreamBuilder builder = new TarStreamBuilder(tarFile, settings);

// Add two files
builder.add(
  new NamedReadableFileAdapter(
    new CharSequenceReadableFile("The contents of this file are secret!"),
    "secret.txt"),
  AbsoluteLocation.ROOT_DIR);

builder.add(
  new NamedReadableFileAdapter(
    new CharSequenceReadableFile("The contents of this file are public!"),
    "public.txt"),
  AbsoluteLocation.ROOT_DIR,
  //
  // Use custom settings for this file
  new TarEntrySettings().
    setEntityMode(UnixEntityMode.forCode(0644)));

// Close the builder to finish the file.
builder.close();