java - Java 通货紧缩/通货膨胀流如何工作？

Question

我正在尝试使用 Deflater 和 InflaterOutputStream 压缩和解压缩一些字节的数据。

问题是压缩似乎有效(我不是 当然，因为即使我有随机测试数据，压缩数据也始终相同)。 但解压根本没有返回任何结果。

我做错了什么？

我的控制台输出:

测试数据:D8A8E00821608F227AE473774E177216

压缩数据:789C

解压后的数据:

我的程序:

SecureRandom random = new SecureRandom();
byte[] testdata = new byte[16];
random.nextBytes(testdata);
System.out.println("Test data: " + DatatypeConverter.printHexBinary(testdata));

byte[] compressed = null;
try (ByteArrayOutputStream buffer = new ByteArrayOutputStream())
{
   try (DeflaterOutputStream stream = new DeflaterOutputStream(buffer))
   {
      stream.write(testdata);
      stream.flush();
      compressed = buffer.toByteArray();
      System.out.println("Compressed data: " + DatatypeConverter.printHexBinary(compressed));
   }
}
catch (IOException e)
{
   System.out.println("IOException during compression.");
}

byte[] decompressed = null;
try (ByteArrayOutputStream buffer = new ByteArrayOutputStream())
{
   try (InflaterOutputStream stream = new InflaterOutputStream(buffer))
   {
      stream.write(compressed);
      stream.flush();
      decompressed = buffer.toByteArray();
      System.out.println("Decompressed data: " + DatatypeConverter.printHexBinary(decompressed));
   }
}
catch (IOException e)
{
   System.out.println("IOException during decompression.");
}

Answer 1

问题是您只是刷新流 - 这并不一定意味着没有更多数据出现，这可能会影响解压。

如果您将两个 flush() 调用更改为 close()，您将看到您获得了适当的数据...或者如您所见使用 try-with-resources 语句，只需关闭内部流，然后等到调用toByteArray:

try (ByteArrayOutputStream buffer = new ByteArrayOutputStream())
{
   try (DeflaterOutputStream stream = new DeflaterOutputStream(buffer))
   {
      stream.write(testdata);
   }
   compressed = buffer.toByteArray();
   System.out.println("Compressed data: " + Arrays.toString(compressed));
}
catch (IOException e)
{
   System.out.println("IOException during compression.");
}

(解压时同上。)