Package org.apache.commons.compress.archivers.sevenz

Class SevenZFile

java.lang.Object
org.apache.commons.compress.archivers.sevenz.SevenZFile
All Implemented Interfaces:
Closeable, AutoCloseable
public class SevenZFile extends Object implements Closeable
Reads a 7z file, using SeekableByteChannel under the covers.

The 7z file format is a flexible container that can contain many compression and encryption types, but at the moment only only Copy, LZMA, LZMA2, BZIP2, Deflate and AES-256 + SHA-256 are supported.

The format is very Windows/Intel specific, so it uses little-endian byte order, doesn't store user/group or permission bits, and represents times using NTFS timestamps (100 nanosecond units since 1 January 1601). Hence the official tools recommend against using it for backup purposes on *nix, and recommend .tar.7z or .tar.lzma or .tar.xz instead.

Both the header and file contents may be compressed and/or encrypted. With both encrypted, neither file names nor file contents can be read, but the use of encryption isn't plausibly deniable.

Multi volume archives can be read by concatenating the parts in correct order - either manually or by using {link org.apache.commons.compress.utils.MultiReadOnlySeekableByteChannel} for example.

Since:
1.6

  • Constructor Details

  • Method Details

    • builder

      public static SevenZFile.Builder builder()
      Creates a new Builder.
      Returns:
      a new Builder.
      Since:
      1.26.0

    • matches

      public static boolean matches(byte[] signature, int length)
      Checks if the signature matches what is expected for a 7z file.
      Parameters:
      signature - the bytes to check
      length - the number of bytes to check
      Returns:
      true, if this is the signature of a 7z archive.
      Since:
      1.8

    • close

      public void close() throws IOException
      Closes the archive.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Throws:
      IOException - if closing the file fails

    • getDefaultName

      public String getDefaultName()
      Gets a default file name from the archive name - if known.

      This implements the same heuristics the 7z tools use. In 7z's case if an archive contains entries without a name - i.e. SevenZArchiveEntry.getName() returns null - then its command line and GUI tools will use this default name when extracting the entries.

      Returns:
      null if the name of the archive is unknown. Otherwise, if the name of the archive has got any extension, it is stripped and the remainder returned. Finally, if the name of the archive hasn't got any extension, then a ~ character is appended to the archive name.
      Since:
      1.19

    • getEntries

      public Iterable<SevenZArchiveEntry> getEntries()
      Gets a copy of meta-data of all archive entries.

      This method only provides meta-data, the entries cannot be used to read the contents, you still need to process all entries in order using getNextEntry() for that.

      The content methods are only available for entries that have already been reached via getNextEntry().

      Returns:
      a copy of meta-data of all archive entries.
      Since:
      1.11

    • getInputStream

      public InputStream getInputStream(SevenZArchiveEntry entry) throws IOException
      Gets an InputStream for reading the contents of the given entry.

      For archives using solid compression randomly accessing entries will be significantly slower than reading the archive sequentially.

      Parameters:
      entry - the entry to get the stream for.
      Returns:
      a stream to read the entry from.
      Throws:
      IOException - if unable to create an input stream from the entry
      Since:
      1.20

    • getNextEntry

      public SevenZArchiveEntry getNextEntry() throws IOException
      Gets the next Archive Entry in this archive.
      Returns:
      the next entry, or null if there are no more entries
      Throws:
      IOException - if the next entry could not be read

    • getStatisticsForCurrentEntry

      public InputStreamStatistics getStatisticsForCurrentEntry()
      Gets statistics for bytes read from the current entry.
      Returns:
      statistics for bytes read from the current entry
      Since:
      1.17

    • read

      public int read() throws IOException
      Reads a byte of data.
      Returns:
      the byte read, or -1 if end of input is reached
      Throws:
      IOException - if an I/O error has occurred

    • read

      public int read(byte[] b) throws IOException
      Reads data into an array of bytes.
      Parameters:
      b - the array to write data to
      Returns:
      the number of bytes read, or -1 if end of input is reached
      Throws:
      IOException - if an I/O error has occurred

    • read

      public int read(byte[] b, int off, int len) throws IOException
      Reads data into an array of bytes.
      Parameters:
      b - the array to write data to
      off - offset into the buffer to start filling at
      len - of bytes to read
      Returns:
      the number of bytes read, or -1 if end of input is reached
      Throws:
      IOException - if an I/O error has occurred

    • toString

      public String toString()
      Overrides:
      toString in class Object