how to extract files from a 7-zip stream in Java without store it on hard disk?

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Solution 1

Commons compress 1.6 and above has support for manipulating 7z format. Try it.

Reference :

http://commons.apache.org/proper/commons-compress/index.html

Sample :

    SevenZFile sevenZFile = new SevenZFile(new File("test-documents.7z"));
    SevenZArchiveEntry entry = sevenZFile.getNextEntry();
    while(entry!=null){
        System.out.println(entry.getName());
        FileOutputStream out = new FileOutputStream(entry.getName());
        byte[] content = new byte[(int) entry.getSize()];
        sevenZFile.read(content, 0, content.length);
        out.write(content);
        out.close();
        entry = sevenZFile.getNextEntry();
    }
    sevenZFile.close();

Solution 2

Since 7z decompression requires random access, you'll have to read the whole stream into a byte[] and use new SevenZFile(new SeekableInMemoryByteChannel(bytes)). (If it's longer than Integer.MAX_VALUE bytes, you'll have to create a custom SeekableByteChannel implementation.) Once the instance is constructed, the process is the same as in SANN3's answer.

If it won't fit in memory and you can't write it to a temporary file, then 7zip isn't a suitable compression algorithm given its need for random access.

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Updated on July 17, 2022

Comments

  • user3330817
    user3330817 over 1 year

    I want to extract some files from a 7-zip byte stream,it can't be stored on hard disk,so I can't use RandomAccessFile class,I have read sevenzipjbinding source code,it also uncompresses the file with some closed source things like lib7-Zip-JBinding.so which wrote by other language.And the method of the official package SevenZip

    SevenZip.Compression.LZMA.Decoder.Code(java.io.InputStream inStream,java.io.OutputStream outStream,long outSize,ICompressProgressInfo progress)

    can only uncompress a single file.

    So how could I uncompress a 7-zip byte stream with pure Java?

    Any guys have solution?

    Sorry for my poor English and I'm waiting for your answers online.

    • MadProgrammer
      MadProgrammer almost 10 years
      Take a look at the Apache Commons, Compress library which I believe has a 7z implementation
  • user3330817
    user3330817 almost 10 years
    tips:the 7-zip byte stream is a socket stream(or http request stream),not a file stored on disk,we can't even use File class.we recently change the compress resolution to xz because 7z doesn't apply a fully-memory resolution.
  • Oleksii K.
    Oleksii K. about 8 years
    I tried Apache Commom-Compress on Android and I want to share my experience here. This solution is completely unacceptable for my goals, because it takes 3 hours (three hours) to decompress single file from 250 Mb to 750 Mb. It seems the implementation is very slow and not optimized. My phone is Nexus 5.
  • Unda
    Unda almost 8 years
    It is true that the Commons Compress library can manipulate 7z format, but apparently not from a stream, as requested by OP.

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