Question

我正在研究java应用程序，我必须将文件管理为tar / zip格式。所以我从csv文件创建tar / zip。现在我正在寻找方法，我可以更快地完成它。因为我必须为数百万个文件运行它。

我正在使用以下代码以及如何使其更快。 Libs正在使用......

org.apache.commons.io

的

FileUtils org.apache.commons.compress.archivers.tar的

TarArchiveEntry

try {
        // Create staging file output stream
        File temp = new File(getFilePath(objectm));
        log.debug("temping " + objectm.getPath());
        outputStream = new FileOutputStream(temp);

        // Create GZip pass-thru stream
        if (isCompressionEnabled) {
            compressionStream = new
                    CompressionStream(outputStream, getCompressionLevel(objectm));
        }

        // Create MD5 hash
        final MessageDigest outputDigest = MessageDigest.getInstance("MD5");
        md5OutputStream = new DigestOutputStream(isCompressionEnabled ? compressionStream : outputStream, outputDigest);

        // Create tar stream
        tarStream = new TarArchiveOutputStream(new BufferedOutputStream(md5OutputStream));
        tarStream.setLongFileMode(TarArchiveOutputStream.LONGFILE_GNU);
        tarStream.setBigNumberMode(TarArchiveOutputStream.BIGNUMBER_STAR);

        // tar the first object
        TarArchiveEntry entry = new TarArchiveEntry(objectm.getHierarchy());
        entry.setSize(objectm.getOriginalSize());
        entry.setModTime(objectm.getLastModified().getMillis());
        tarStream.putArchiveEntry(entry);
        org.apache.commons.io.IOUtils.copyLarge(inputStream, tarStream);


        // Collect properties to return
        String digest = Hex.encodeHexString(outputDigest.digest());
        objectm.setChecksum(digest);
        objectm.setDate(DateTime.now());
        objectm.setCompressSize(FileUtils.sizeOf(temp));          
        tarStream.finish();
        log.debug("Completed.");

    } catch (Exception e) {
        throw new Exception("Exception: Creating tar" , e);
    } finally {
        org.apache.cobjectmmons.io.IOUtils.closeQuietly(inputStream);
        org.apache.cobjectmmons.io.IOUtils.closeQuietly(tarStream);
        org.apache.cobjectmmons.io.IOUtils.closeQuietly(cobjectmpressionStream);
        org.apache.cobjectmmons.io.IOUtils.closeQuietly(md5OutputStream);
        org.apache.cobjectmmons.io.IOUtils.closeQuietly(outputStream);
    }

在第二种方法中，我们将对象从temp移动到实际位置。

try {
        File src = new File(getFilePath(objectm));
        File dst = new File(sDestinationFile);
        FileUtils.moveFile(src, dst);
        boolean readableFlag = dst.setReadOnly();
    } catch (IOException e) {
        throw new Exception("Unable to move to destination.", e);
    }

Answer 1

使用LZ4，这是目前压缩文件最快的算法。代码示例如下。

LZ4Factory factory = LZ4Factory.fastestInstance();

byte[] data = "12345345234572".getBytes("UTF-8");
final int decompressedLength = data.length;

// compress data
LZ4Compressor compressor = factory.fastCompressor();
int maxCompressedLength = compressor.maxCompressedLength(decompressedLength);
byte[] compressed = new byte[maxCompressedLength];
int compressedLength = compressor.compress(data, 0, decompressedLength, compressed, 0, maxCompressedLength);

// decompress data
// - method 1: when the decompressed length is known
LZ4FastDecompressor decompressor = factory.fastDecompressor();
byte[] restored = new byte[decompressedLength];
int compressedLength2 = decompressor.decompress(compressed, 0, restored, 0, decompressedLength);
// compressedLength == compressedLength2

// - method 2: when the compressed length is known (a little slower)
// the destination buffer needs to be over-sized
LZ4SafeDecompressor decompressor2 = factory.safeDecompressor();
int decompressedLength2 = decompressor2.decompress(compressed, 0, compressedLength, restored, 0);
// decompressedLength == decompressedLength2

摘自https://github.com/jpountz/lz4-java

如何在java中更快地压缩到归档文件

1 个答案: