Question

我想将一些字节数据插入到mysql VARBINARY列中。数据很大，所以我想以压缩的方式存储它。

我正在使用Percona 5.6 Mysql。我想在Java中模拟mysql的COMPRESS函数，然后将结果插入数据库中。我想使用MySql DECOMPRESS函数来访问这些数据。有办法吗？

我尝试使用标准的java.zip包。但它不起作用。

修改即可。换句话说，PHP的gzcompress（ZLIB）的Java等价物是什么？

Answer 1

COMPRESS的结果是未压缩数据的四字节小端长度，后跟包含压缩数据的zlib流。

您可以使用Java中的Deflater类来压缩到zlib流。以四字节长度表示结果。

Answer 2

解决方案：实施MYSQL压缩和DECOMPRESS

//Compress byte stream using ZLib compression
  public static byte[] compressZLib(byte[] data)  {
    Deflater deflater = new Deflater();
    deflater.setInput(data);
    deflater.finish();

    ByteArrayOutputStream outputStream = new ByteArrayOutputStream(data.length);
    byte[] buffer = new byte[1024];
    while (!deflater.finished()) {
      int count = deflater.deflate(buffer); // returns the generated code... index
      outputStream.write(buffer, 0, count);
    }
    try {
      outputStream.close();
    } catch (IOException e) {
    }
    return outputStream.toByteArray();
  }

//MYSQL COMPRESS.
  public static byte[] compressMySQL(byte[] data)  {
    byte[] lengthBeforeCompression = ByteBuffer.allocate(Integer.SIZE / Byte.SIZE).order(ByteOrder.LITTLE_ENDIAN).putInt(data.length).array();
    ByteArrayOutputStream resultStream = new ByteArrayOutputStream();
    try {
      resultStream.write( lengthBeforeCompression );
      resultStream.write( compressZLib(data));
      resultStream.close();
    } catch (IOException e) {
    }
    return resultStream.toByteArray( );
  }

//Decompress using ZLib
  public static byte[] decompressZLib(byte[] data) {
    Inflater inflater = new Inflater();
    inflater.setInput(data);
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream(data.length);
    byte[] buffer = new byte[1024];
    try {
      while (!inflater.finished()) {
        int count = inflater.inflate(buffer);
        outputStream.write(buffer, 0, count);
      }
      outputStream.close();
    }catch (IOException ioe) {
    } catch (DataFormatException e) {
    }
    return outputStream.toByteArray();
  }

  //MYSQL DECOMPRESS
  public static byte[] decompressSQLCompression(byte[] input) {
    //ignore first four bytes which denote length of uncompressed data. use rest of the array for decompression
    byte[] data= Arrays.copyOfRange(input,4,input.length);
    return decompressZLib(data);
  }

Java模拟MySQL COMRESS DECOMPRESS函数

2 个答案: