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<?xml version="1.0"?>
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<document>
<properties>
<title>Commons Compress Examples</title>
<author email="dev@commons.apache.org">Commons Documentation Team</author>
</properties>
<body>
<section name="General Notes">
<subsection name="Archivers and Compressors">
<p>Commons Compress calls all formats that compress a single
stream of data compressor formats while all formats that
collect multiple entries inside a single (potentially
compressed) archive are archiver formats.</p>
<p>The compressor formats supported are gzip, bzip2, xz, lzma,
Pack200, DEFLATE, Brotli, DEFLATE64, ZStandard and Z, the archiver formats are 7z, ar, arj,
cpio, dump, tar and zip. Pack200 is a special case as it can
only compress JAR files.</p>
<p>We currently only provide read support for arj,
dump, Brotli, DEFLATE64 and Z. arj can only read uncompressed archives, 7z can read
archives with many compression and encryption algorithms
supported by 7z but doesn't support encryption when writing
archives.</p>
</subsection>
<subsection name="Buffering">
<p>The stream classes all wrap around streams provided by the
calling code and they work on them directly without any
additional buffering. On the other hand most of them will
benefit from buffering so it is highly recommended that
users wrap their stream
in <code>Buffered<em>(In|Out)</em>putStream</code>s before
using the Commons Compress API.</p>
</subsection>
<subsection name="Factories">
<p>Compress provides factory methods to create input/output
streams based on the names of the compressor or archiver
format as well as factory methods that try to guess the
format of an input stream.</p>
<p>To create a compressor writing to a given output by using
the algorithm name:</p>
<source><![CDATA[
CompressorOutputStream gzippedOut = new CompressorStreamFactory()
.createCompressorOutputStream(CompressorStreamFactory.GZIP, myOutputStream);
]]></source>
<p>Make the factory guess the input format for a given
archiver stream:</p>
<source><![CDATA[
ArchiveInputStream input = new ArchiveStreamFactory()
.createArchiveInputStream(originalInput);
]]></source>
<p>Make the factory guess the input format for a given
compressor stream:</p>
<source><![CDATA[
CompressorInputStream input = new CompressorStreamFactory()
.createCompressorInputStream(originalInput);
]]></source>
<p>Note that there is no way to detect the lzma or Brotli formats so only
the two-arg version of
<code>createCompressorInputStream</code> can be used. Prior
to Compress 1.9 the .Z format hasn't been auto-detected
either.</p>
</subsection>
<subsection name="Restricting Memory Usage">
<p>Starting with Compress 1.14
<code>CompressorStreamFactory</code> has an optional
constructor argument that can be used to set an upper limit of
memory that may be used while decompressing or compressing a
stream. As of 1.14 this setting only affects decompressing Z,
XZ and LZMA compressed streams.</p>
<p>For the Snappy and LZ4 formats the amount of memory used
during compression is directly proportional to the window
size.</p>
</subsection>
<subsection name="Statistics">
<p>Starting with Compress 1.17 most of the
<code>CompressorInputStream</code> implementations as well as
<code>ZipArchiveInputStream</code> and all streams returned by
<code>ZipFile.getInputStream</code> implement the
<code>InputStreamStatistics</code>
interface. <code>SevenZFile</code> provides statistics for the
current entry via the
<code>getStatisticsForCurrentEntry</code> method. This
interface can be used to track progress while extracting a
stream or to detect potential <a
href="https://en.wikipedia.org/wiki/Zip_bomb">zip bombs</a>
when the compression ration becomes suspiciously large.</p>
</subsection>
</section>
<section name="Archivers">
<subsection name="Unsupported Features">
<p>Many of the supported formats have developed different
dialects and extensions and some formats allow for features
(not yet) supported by Commons Compress.</p>
<p>The <code>ArchiveInputStream</code> class provides a method
<code>canReadEntryData</code> that will return false if
Commons Compress can detect that an archive uses a feature
that is not supported by the current implementation. If it
returns false you should not try to read the entry but skip
over it.</p>
</subsection>
<subsection name="Entry Names">
<p>All archive formats provide meta data about the individual
archive entries via instances of <code>ArchiveEntry</code> (or
rather subclasses of it). When reading from an archive the
information provided the <code>getName</code> method is the
raw name as stored inside of the archive. There is no
guarantee the name represents a relative file name or even a
valid file name on your target operating system at all. You
should double check the outcome when you try to create file
names from entry names.</p>
</subsection>
<subsection name="Common Extraction Logic">
<p>Apart from 7z all formats provide a subclass of
<code>ArchiveInputStream</code> that can be used to create an
archive. For 7z <code>SevenZFile</code> provides a similar API
that does not represent a stream as our implementation
requires random access to the input and cannot be used for
general streams. The ZIP implementation can benefit a lot from
random access as well, see the <a
href="zip.html#ZipArchiveInputStream%20vs$20ZipFile">zip
page</a> for details.</p>
<p>Assuming you want to extract an archive to a target
directory you'd call <code>getNextEntry</code>, verify the
entry can be read, construct a sane file name from the entry's
name, create a <codee>File</codee> and write all contents to
it - here <code>IOUtils.copy</code> may come handy. You do so
for every entry until <code>getNextEntry</code> returns
<code>null</code>.</p>
<p>A skeleton might look like:</p>
<source><![CDATA[
File targetDir = ...
try (ArchiveInputStream i = ... create the stream for your format, use buffering...) {
ArchiveEntry entry = null;
while ((entry = i.getNextEntry()) != null) {
if (!i.canReadEntryData(entry)) {
// log something?
continue;
}
String name = fileName(targetDir, entry);
File f = new File(name);
if (entry.isDirectory()) {
if (!f.isDirectory() && !f.mkdirs()) {
throw new IOException("failed to create directory " + f);
}
} else {
File parent = f.getParentFile();
if (!parent.isDirectory() && !parent.mkdirs()) {
throw new IOException("failed to create directory " + parent);
}
try (OutputStream o = Files.newOutputStream(f.toPath())) {
IOUtils.copy(i, o);
}
}
}
}
]]></source>
<p>where the hypothetical <code>fileName</code> method is
written by you and provides the absolute name for the file
that is going to be written on disk. Here you should perform
checks that ensure the resulting file name actually is a valid
file name on your operating system or belongs to a file inside
of <code>targetDir</code> when using the entry's name as
input.</p>
<p>If you want to combine an archive format with a compression
format - like when reading a "tar.gz" file - you wrap the
<code>ArchiveInputStream</code> around
<code>CompressorInputStream</code> for example:</p>
<source><![CDATA[
try (InputStream fi = new Files.newInputStream(Paths.get("my.tar.gz"));
InputStream bi = new BufferedInputStream(fi);
InputStream gzi = new GzipCompressorInputStream(bi);
ArchiveInputStream o = new TarArchiveInputStream(gzi)) {
}
]]></source>
</subsection>
<subsection name="Common Archival Logic">
<p>Apart from 7z all formats that support writing provide a
subclass of <code>ArchiveOutputStream</code> that can be used
to create an archive. For 7z <code>SevenZOutputFile</code>
provides a similar API that does not represent a stream as our
implementation requires random access to the output and cannot
be used for general streams. The
<code>ZipArchiveOutputStream</code> class will benefit from
random access as well but can be used for non-seekable streams
- but not all features will be available and the archive size
might be slightly bigger, see <a
href="zip.html#ZipArchiveOutputStream">the zip page</a> for
details.</p>
<p>Assuming you want to add a collection of files to an
archive, you can first use <code>createArchiveEntry</code> for
each file. In general this will set a few flags (usually the
last modified time, the size and the information whether this
is a file or directory) based on the <code>File</code>
instance. Alternatively you can create the
<code>ArchiveEntry</code> subclass corresponding to your
format directly. Often you may want to set additional flags
like file permissions or owner information before adding the
entry to the archive.</p>
<p>Next you use <code>putArchiveEntry</code> in order to add
the entry and then start using <code>write</code> to add the
content of the entry - here <code>IOUtils.copy</code> may
come handy. Finally you invoke
<code>closeArchiveEntry</code> once you've written all content
and before you add the next entry.</p>
<p>Once all entries have been added you'd invoke
<code>finish</code> and finally <code>close</code> the
stream.</p>
<p>A skeleton might look like:</p>
<source><![CDATA[
Collection<File> filesToArchive = ...
try (ArchiveOutputStream o = ... create the stream for your format ...) {
for (File f : filesToArchive) {
// maybe skip directories for formats like AR that don't store directories
ArchiveEntry entry = o.createArchiveEntry(f, entryName(f));
// potentially add more flags to entry
o.putArchiveEntry(entry);
if (f.isFile()) {
try (InputStream i = Files.newInputStream(f.toPath())) {
IOUtils.copy(i, o);
}
}
o.closeArchiveEntry();
}
out.finish();
}
]]></source>
<p>where the hypothetical <code>entryName</code> method is
written by you and provides the name for the entry as it is
going to be written to the archive.</p>
<p>If you want to combine an archive format with a compression
format - like when creating a "tar.gz" file - you wrap the
<code>ArchiveOutputStream</code> around a
<code>CompressorOutputStream</code> for example:</p>
<source><![CDATA[
try (OutputStream fo = Files.newOutputStream(Paths.get("my.tar.gz"));
OutputStream gzo = new GzipCompressorOutputStream(fo);
ArchiveOutputStream o = new TarArchiveOutputStream(gzo)) {
}
]]></source>
</subsection>
<subsection name="7z">
<p>Note that Commons Compress currently only supports a subset
of compression and encryption algorithms used for 7z archives.
For writing only uncompressed entries, LZMA, LZMA2, BZIP2 and
Deflate are supported - in addition to those reading supports
AES-256/SHA-256 and DEFLATE64.</p>
<p>Multipart archives are not supported at all.</p>
<p>7z archives can use multiple compression and encryption
methods as well as filters combined as a pipeline of methods
for its entries. Prior to Compress 1.8 you could only specify
a single method when creating archives - reading archives
using more than one method has been possible before. Starting
with Compress 1.8 it is possible to configure the full
pipeline using the <code>setContentMethods</code> method of
<code>SevenZOutputFile</code>. Methods are specified in the
order they appear inside the pipeline when creating the
archive, you can also specify certain parameters for some of
the methods - see the Javadocs of
<code>SevenZMethodConfiguration</code> for details.</p>
<p>When reading entries from an archive the
<code>getContentMethods</code> method of
<code>SevenZArchiveEntry</code> will properly represent the
compression/encryption/filter methods but may fail to
determine the configuration options used. As of Compress 1.8
only the dictionary size used for LZMA2 can be read.</p>
<p>Currently solid compression - compressing multiple files
as a single block to benefit from patterns repeating accross
files - is only supported when reading archives. This also
means compression ratio will likely be worse when using
Commons Compress compared to the native 7z executable.</p>
<p>Reading or writing requires a
<code>SeekableByteChannel</code> that will be obtained
transparently when reading from or writing to a file. The
class
<code>org.apache.commons.compress.utils.SeekableInMemoryByteChannel</code>
allows you to read from or write to an in-memory archive.</p>
<p>Adding an entry to a 7z archive:</p>
<source><![CDATA[
SevenZOutputFile sevenZOutput = new SevenZOutputFile(file);
SevenZArchiveEntry entry = sevenZOutput.createArchiveEntry(fileToArchive, name);
sevenZOutput.putArchiveEntry(entry);
sevenZOutput.write(contentOfEntry);
sevenZOutput.closeArchiveEntry();
]]></source>
<p>Uncompressing a given 7z archive (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
SevenZFile sevenZFile = new SevenZFile(new File("archive.7z"));
SevenZArchiveEntry entry = sevenZFile.getNextEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
sevenZFile.read(content, offset, content.length - offset);
}
]]></source>
<p>Uncompressing a given in-memory 7z archive:</p>
<source><![CDATA[
byte[] inputData; // 7z archive contents
SeekableInMemoryByteChannel inMemoryByteChannel = new SeekableInMemoryByteChannel(inputData);
SevenZFile sevenZFile = new SevenZFile(inMemoryByteChannel);
SevenZArchiveEntry entry = sevenZFile.getNextEntry();
sevenZFile.read(); // read current entry's data
]]></source>
<h4><a name="Encrypted 7z Archives"></a>Encrypted 7z Archives</h4>
<p>Currently Compress supports reading but not writing of
encrypted archives. When reading an encrypted archive a
password has to be provided to one of
<code>SevenZFile</code>'s constructors. If you try to read
an encrypted archive without specifying a password a
<code>PasswordRequiredException</code> (a subclass of
<code>IOException</code>) will be thrown.</p>
<p>When specifying the password as a <code>byte[]</code> one
common mistake is to use the wrong encoding when creating
the <code>byte[]</code> from a <code>String</code>. The
<code>SevenZFile</code> class expects the bytes to
correspond to the UTF16-LE encoding of the password. An
example of reading an encrypted archive is</p>
<source><![CDATA[
SevenZFile sevenZFile = new SevenZFile(new File("archive.7z"), "secret".getBytes(StandardCharsets.UTF_16LE));
SevenZArchiveEntry entry = sevenZFile.getNextEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
sevenZFile.read(content, offset, content.length - offset);
}
]]></source>
</subsection>
<subsection name="ar">
<p>In addition to the information stored
in <code>ArchiveEntry</code> a <code>ArArchiveEntry</code>
stores information about the owner user and group as well as
Unix permissions.</p>
<p>Adding an entry to an ar archive:</p>
<source><![CDATA[
ArArchiveEntry entry = new ArArchiveEntry(name, size);
arOutput.putArchiveEntry(entry);
arOutput.write(contentOfEntry);
arOutput.closeArchiveEntry();
]]></source>
<p>Reading entries from an ar archive:</p>
<source><![CDATA[
ArArchiveEntry entry = (ArArchiveEntry) arInput.getNextEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
arInput.read(content, offset, content.length - offset);
}
]]></source>
<p>Traditionally the AR format doesn't allow file names longer
than 16 characters. There are two variants that circumvent
this limitation in different ways, the GNU/SRV4 and the BSD
variant. Commons Compress 1.0 to 1.2 can only read archives
using the GNU/SRV4 variant, support for the BSD variant has
been added in Commons Compress 1.3. Commons Compress 1.3
also optionally supports writing archives with file names
longer than 16 characters using the BSD dialect, writing
the SVR4/GNU dialect is not supported.</p>
<table>
<thead>
<tr>
<th>Version of Apache Commons Compress</th>
<th>Support for Traditional AR Format</th>
<th>Support for GNU/SRV4 Dialect</th>
<th>Support for BSD Dialect</th>
</tr>
</thead>
<tbody>
<tr>
<td>1.0 to 1.2</td>
<td>read/write</td>
<td>read</td>
<td>-</td>
</tr>
<tr>
<td>1.3 and later</td>
<td>read/write</td>
<td>read</td>
<td>read/write</td>
</tr>
</tbody>
</table>
<p>It is not possible to detect the end of an AR archive in a
reliable way so <code>ArArchiveInputStream</code> will read
until it reaches the end of the stream or fails to parse the
stream's content as AR entries.</p>
</subsection>
<subsection name="arj">
<p>Note that Commons Compress doesn't support compressed,
encrypted or multi-volume ARJ archives, yet.</p>
<p>Uncompressing a given arj archive (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
ArjArchiveEntry entry = arjInput.getNextEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
arjInput.read(content, offset, content.length - offset);
}
]]></source>
</subsection>
<subsection name="cpio">
<p>In addition to the information stored
in <code>ArchiveEntry</code> a <code>CpioArchiveEntry</code>
stores various attributes including information about the
original owner and permissions.</p>
<p>The cpio package supports the "new portable" as well as the
"old" format of CPIO archives in their binary, ASCII and
"with CRC" variants.</p>
<p>Adding an entry to a cpio archive:</p>
<source><![CDATA[
CpioArchiveEntry entry = new CpioArchiveEntry(name, size);
cpioOutput.putArchiveEntry(entry);
cpioOutput.write(contentOfEntry);
cpioOutput.closeArchiveEntry();
]]></source>
<p>Reading entries from an cpio archive:</p>
<source><![CDATA[
CpioArchiveEntry entry = cpioInput.getNextCPIOEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
cpioInput.read(content, offset, content.length - offset);
}
]]></source>
<p>Traditionally CPIO archives are written in blocks of 512
bytes - the block size is a configuration parameter of the
<code>Cpio*Stream</code>'s constuctors. Starting with version
1.5 <code>CpioArchiveInputStream</code> will consume the
padding written to fill the current block when the end of the
archive is reached. Unfortunately many CPIO implementations
use larger block sizes so there may be more zero-byte padding
left inside the original input stream after the archive has
been consumed completely.</p>
</subsection>
<subsection name="jar">
<p>In general, JAR archives are ZIP files, so the JAR package
supports all options provided by the <a href="#zip">ZIP</a> package.</p>
<p>To be interoperable JAR archives should always be created
using the UTF-8 encoding for file names (which is the
default).</p>
<p>Archives created using <code>JarArchiveOutputStream</code>
will implicitly add a <code>JarMarker</code> extra field to
the very first archive entry of the archive which will make
Solaris recognize them as Java archives and allows them to
be used as executables.</p>
<p>Note that <code>ArchiveStreamFactory</code> doesn't
distinguish ZIP archives from JAR archives, so if you use
the one-argument <code>createArchiveInputStream</code>
method on a JAR archive, it will still return the more
generic <code>ZipArchiveInputStream</code>.</p>
<p>The <code>JarArchiveEntry</code> class contains fields for
certificates and attributes that are planned to be supported
in the future but are not supported as of Compress 1.0.</p>
<p>Adding an entry to a jar archive:</p>
<source><![CDATA[
JarArchiveEntry entry = new JarArchiveEntry(name, size);
entry.setSize(size);
jarOutput.putArchiveEntry(entry);
jarOutput.write(contentOfEntry);
jarOutput.closeArchiveEntry();
]]></source>
<p>Reading entries from an jar archive:</p>
<source><![CDATA[
JarArchiveEntry entry = jarInput.getNextJarEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
jarInput.read(content, offset, content.length - offset);
}
]]></source>
</subsection>
<subsection name="dump">
<p>In addition to the information stored
in <code>ArchiveEntry</code> a <code>DumpArchiveEntry</code>
stores various attributes including information about the
original owner and permissions.</p>
<p>As of Commons Compress 1.3 only dump archives using the
new-fs format - this is the most common variant - are
supported. Right now this library supports uncompressed and
ZLIB compressed archives and can not write archives at
all.</p>
<p>Reading entries from an dump archive:</p>
<source><![CDATA[
DumpArchiveEntry entry = dumpInput.getNextDumpEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
dumpInput.read(content, offset, content.length - offset);
}
]]></source>
<p>Prior to version 1.5 <code>DumpArchiveInputStream</code>
would close the original input once it had read the last
record. Starting with version 1.5 it will not close the
stream implicitly.</p>
</subsection>
<subsection name="tar">
<p>The TAR package has a <a href="tar.html">dedicated
documentation page</a>.</p>
<p>Adding an entry to a tar archive:</p>
<source><![CDATA[
TarArchiveEntry entry = new TarArchiveEntry(name);
entry.setSize(size);
tarOutput.putArchiveEntry(entry);
tarOutput.write(contentOfEntry);
tarOutput.closeArchiveEntry();
]]></source>
<p>Reading entries from an tar archive:</p>
<source><![CDATA[
TarArchiveEntry entry = tarInput.getNextTarEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
tarInput.read(content, offset, content.length - offset);
}
]]></source>
</subsection>
<subsection name="zip">
<p>The ZIP package has a <a href="zip.html">dedicated
documentation page</a>.</p>
<p>Adding an entry to a zip archive:</p>
<source><![CDATA[
ZipArchiveEntry entry = new ZipArchiveEntry(name);
entry.setSize(size);
zipOutput.putArchiveEntry(entry);
zipOutput.write(contentOfEntry);
zipOutput.closeArchiveEntry();
]]></source>
<p><code>ZipArchiveOutputStream</code> can use some internal
optimizations exploiting <code>SeekableByteChannel</code> if it
knows it is writing to a seekable output rather than a non-seekable
stream. If you are writing to a file, you should use the
constructor that accepts a <code>File</code> or
<code>SeekableByteChannel</code> argument rather
than the one using an <code>OutputStream</code> or the
factory method in <code>ArchiveStreamFactory</code>.</p>
<p>Reading entries from an zip archive:</p>
<source><![CDATA[
ZipArchiveEntry entry = zipInput.getNextZipEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
zipInput.read(content, offset, content.length - offset);
}
]]></source>
<p>Reading entries from an zip archive using the
recommended <code>ZipFile</code> class:</p>
<source><![CDATA[
ZipArchiveEntry entry = zipFile.getEntry(name);
InputStream content = zipFile.getInputStream(entry);
try {
READ UNTIL content IS EXHAUSTED
} finally {
content.close();
}
]]></source>
<p>Reading entries from an in-memory zip archive using
<code>SeekableInMemoryByteChannel</code> and <code>ZipFile</code> class:</p>
<source><![CDATA[
byte[] inputData; // zip archive contents
SeekableInMemoryByteChannel inMemoryByteChannel = new SeekableInMemoryByteChannel(inputData);
ZipFile zipFile = new ZipFile(inMemoryByteChannel);
ZipArchiveEntry archiveEntry = zipFile.getEntry("entryName");
InputStream inputStream = zipFile.getInputStream(archiveEntry);
inputStream.read() // read data from the input stream
]]></source>
<p>Creating a zip file with multiple threads:</p>
A simple implementation to create a zip file might look like this:
<source>
public class ScatterSample {
ParallelScatterZipCreator scatterZipCreator = new ParallelScatterZipCreator();
ScatterZipOutputStream dirs = ScatterZipOutputStream.fileBased(File.createTempFile("scatter-dirs", "tmp"));
public ScatterSample() throws IOException {
}
public void addEntry(ZipArchiveEntry zipArchiveEntry, InputStreamSupplier streamSupplier) throws IOException {
if (zipArchiveEntry.isDirectory() &amp;&amp; !zipArchiveEntry.isUnixSymlink())
dirs.addArchiveEntry(ZipArchiveEntryRequest.createZipArchiveEntryRequest(zipArchiveEntry, streamSupplier));
else
scatterZipCreator.addArchiveEntry( zipArchiveEntry, streamSupplier);
}
public void writeTo(ZipArchiveOutputStream zipArchiveOutputStream)
throws IOException, ExecutionException, InterruptedException {
dirs.writeTo(zipArchiveOutputStream);
dirs.close();
scatterZipCreator.writeTo(zipArchiveOutputStream);
}
}
</source>
</subsection>
</section>
<section name="Compressors">
<subsection name="Concatenated Streams">
<p>For the bzip2, gzip and xz formats as well as the framed
lz4 format a single compressed file
may actually consist of several streams that will be
concatenated by the command line utilities when decompressing
them. Starting with Commons Compress 1.4 the
<code>*CompressorInputStream</code>s for these formats support
concatenating streams as well, but they won't do so by
default. You must use the two-arg constructor and explicitly
enable the support.</p>
</subsection>
<subsection name="Brotli">
<p>The implementation of this package is provided by the
<a href="https://github.com/google/brotli">Google Brotli dec</a> library.</p>
<p>Uncompressing a given Brotli compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.br"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
BrotliCompressorInputStream brIn = new BrotliCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = brIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
brIn.close();
]]></source>
</subsection>
<subsection name="bzip2">
<p>Note that <code>BZipCompressorOutputStream</code> keeps
hold of some big data structures in memory. While it is
recommended for <em>any</em> stream that you close it as soon as
you no longer need it, this is even more important
for <code>BZipCompressorOutputStream</code>.</p>
<p>Uncompressing a given bzip2 compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.bz2"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
BZip2CompressorInputStream bzIn = new BZip2CompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = bzIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
bzIn.close();
]]></source>
<p>Compressing a given file using bzip2 (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.gz"));
BufferedOutputStream out = new BufferedOutputStream(fout);
BZip2CompressorOutputStream bzOut = new BZip2CompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
bzOut.write(buffer, 0, n);
}
bzOut.close();
in.close();
]]></source>
</subsection>
<subsection name="DEFLATE">
<p>The implementation of the DEFLATE/INFLATE code used by this
package is provided by the <code>java.util.zip</code> package
of the Java class library.</p>
<p>Uncompressing a given DEFLATE compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("some-file"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
DeflateCompressorInputStream defIn = new DeflateCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = defIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
defIn.close();
]]></source>
<p>Compressing a given file using DEFLATE (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("some-file"));
BufferedOutputStream out = new BufferedOutputStream(fout);
DeflateCompressorOutputStream defOut = new DeflateCompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
defOut.write(buffer, 0, n);
}
defOut.close();
in.close();
]]></source>
</subsection>
<subsection name="DEFLATE64">
<p>Uncompressing a given DEFLATE64 compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("some-file"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
Deflate64CompressorInputStream defIn = new Deflate64CompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = defIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
defIn.close();
]]></source>
</subsection>
<subsection name="gzip">
<p>The implementation of the DEFLATE/INFLATE code used by this
package is provided by the <code>java.util.zip</code> package
of the Java class library.</p>
<p>Uncompressing a given gzip compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.gz"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
GzipCompressorInputStream gzIn = new GzipCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = gzIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
gzIn.close();
]]></source>
<p>Compressing a given file using gzip (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.gz"));
BufferedOutputStream out = new BufferedOutputStream(fout);
GzipCompressorOutputStream gzOut = new GzipCompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
gzOut.write(buffer, 0, n);
}
gzOut.close();
in.close();
]]></source>
</subsection>
<subsection name="LZ4">
<p>There are two different "formats" used for <a
href="http://lz4.github.io/lz4/">lz4</a>. The format called
"block format" only contains the raw compressed data while the
other provides a higher level "frame format" - Commons
Compress offers two different stream classes for reading or
writing either format.</p>
<p>Uncompressing a given frame LZ4 file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.lz4"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
FramedLZ4CompressorInputStream zIn = new FramedLZ4CompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = zIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
zIn.close();
]]></source>
<p>Compressing a given file using the LZ4 frame format (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.lz4"));
BufferedOutputStream out = new BufferedOutputStream(fout);
FramedLZ4CompressorOutputStream lzOut = new FramedLZ4CompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
lzOut.write(buffer, 0, n);
}
lzOut.close();
in.close();
]]></source>
</subsection>
<subsection name="lzma">
<p>The implementation of this package is provided by the
public domain <a href="https://tukaani.org/xz/java.html">XZ
for Java</a> library.</p>
<p>Uncompressing a given lzma compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.lzma"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
LZMACompressorInputStream lzmaIn = new LZMACompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = xzIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
lzmaIn.close();
]]></source>
<p>Compressing a given file using lzma (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.lzma"));
BufferedOutputStream out = new BufferedOutputStream(fout);
LZMACompressorOutputStream lzOut = new LZMACompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
lzOut.write(buffer, 0, n);
}
lzOut.close();
in.close();
]]></source>
</subsection>
<subsection name="Pack200">
<p>The Pack200 package has a <a href="pack200.html">dedicated
documentation page</a>.</p>
<p>The implementation of this package is provided by
the <code>java.util.zip</code> package of the Java class
library.</p>
<p>Uncompressing a given pack200 compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.pack"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.jar"));
Pack200CompressorInputStream pIn = new Pack200CompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = pIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
pIn.close();
]]></source>
<p>Compressing a given jar using pack200 (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.jar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.pack"));
BufferedOutputStream out = new BufferedInputStream(fout);
Pack200CompressorOutputStream pOut = new Pack200CompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
pOut.write(buffer, 0, n);
}
pOut.close();
in.close();
]]></source>
</subsection>
<subsection name="Snappy">
<p>There are two different "formats" used for <a
href="https://github.com/google/snappy/">Snappy</a>, one only
contains the raw compressed data while the other provides a
higher level "framing format" - Commons Compress offers two
different stream classes for reading either format.</p>
<p>Starting with 1.12 we've added support for different
dialects of the framing format that can be specified when
constructing the stream. The <code>STANDARD</code> dialect
follows the "framing format" specification while the
<code>IWORK_ARCHIVE</code> dialect can be used to parse IWA
files that are part of Apple's iWork 13 format. If no dialect
has been specified, <code>STANDARD</code> is used. Only the
<code>STANDARD</code> format can be detected by
<code>CompressorStreamFactory</code>.</p>
<p>Uncompressing a given framed Snappy file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.sz"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
FramedSnappyCompressorInputStream zIn = new FramedSnappyCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = zIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
zIn.close();
]]></source>
<p>Compressing a given file using framed Snappy (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.sz"));
BufferedOutputStream out = new BufferedOutputStream(fout);
FramedSnappyCompressorOutputStream snOut = new FramedSnappyCompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
snOut.write(buffer, 0, n);
}
snOut.close();
in.close();
]]></source>
</subsection>
<subsection name="XZ">
<p>The implementation of this package is provided by the
public domain <a href="https://tukaani.org/xz/java.html">XZ
for Java</a> library.</p>
<p>When you try to open an XZ stream for reading using
<code>CompressorStreamFactory</code>, Commons Compress will
check whether the XZ for Java library is available. Starting
with Compress 1.9 the result of this check will be cached
unless Compress finds OSGi classes in its classpath. You can
use <code>XZUtils#setCacheXZAvailability</code> to overrride
this default behavior.</p>
<p>Uncompressing a given XZ compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.xz"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
XZCompressorInputStream xzIn = new XZCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = xzIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
xzIn.close();
]]></source>
<p>Compressing a given file using XZ (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.xz"));
BufferedOutputStream out = new BufferedInputStream(fout);
XZCompressorOutputStream xzOut = new XZCompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
xzOut.write(buffer, 0, n);
}
xzOut.close();
in.close();
]]></source>
</subsection>
<subsection name="Z">
<p>Uncompressing a given Z compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.Z"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
ZCompressorInputStream zIn = new ZCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = zIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
zIn.close();
]]></source>
</subsection>
<subsection name="Zstandard">
<p>The implementation of this package is provided by the
<a href="https://github.com/luben/zstd-jni">Zstandard JNI</a> library.</p>
<p>Uncompressing a given Zstandard compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.zstd"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
ZstdCompressorInputStream zsIn = new ZstdCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = zsIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
zsIn.close();
]]></source>
<p>Compressing a given file using the Zstandard format (you
would certainly add exception handling and make sure all
streams get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.zstd"));
BufferedOutputStream out = new BufferedOutputStream(fout);
ZstdCompressorOutputStream zOut = new ZstdCompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
zOut.write(buffer, 0, n);
}
zOut.close();
in.close();
]]></source>
</subsection>
</section>
<section name="Extending Commons Compress">
<p>
Starting in release 1.13, it is now possible to add Compressor- and ArchiverStream implementations using the
Java's <a href="https://docs.oracle.com/javase/7/docs/api/java/util/ServiceLoader.html">ServiceLoader</a>
mechanism.
</p>
<subsection name="Extending Commons Compress Compressors">
<p>
To provide your own compressor, you must make available on the classpath a file called
<code>META-INF/services/org.apache.commons.compress.compressors.CompressorStreamProvider</code>.
</p>
<p>
This file MUST contain one fully-qualified class name per line.
</p>
<p>
For example:
</p>
<pre>org.apache.commons.compress.compressors.TestCompressorStreamProvider</pre>
<p>
This class MUST implement the Commons Compress interface
<a href="apidocs/org/apache/commons/compress/compressors/CompressorStreamProvider.html">org.apache.commons.compress.compressors.CompressorStreamProvider</a>.
</p>
</subsection>
<subsection name="Extending Commons Compress Archivers">
<p>
To provide your own compressor, you must make available on the classpath a file called
<code>META-INF/services/org.apache.commons.compress.archivers.ArchiveStreamProvider</code>.
</p>
<p>
This file MUST contain one fully-qualified class name per line.
</p>
<p>
For example:
</p>
<pre>org.apache.commons.compress.archivers.TestArchiveStreamProvider</pre>
<p>
This class MUST implement the Commons Compress interface
<a href="apidocs/org/apache/commons/compress/archivers/ArchiveStreamProvider.html">org.apache.commons.compress.archivers.ArchiveStreamProvider</a>.
</p>
</subsection>
</section>
</body>
</document>