MQTT数据压缩

Question

目前，我正在尝试找出MQTT是否支持数据的自动压缩。例如，如果我将MQTT与TLS结合使用，则可以使用TLS的压缩选项。MQTT有没有类似的东西？或者发布应用程序必须自己压缩数据，然后才能使用MQTT发送压缩数据？

到目前为止，我已经到处阅读，没有找到任何关于MQTT是否支持数据压缩的具体信息。

感谢您的帮助:)

Answer 1

MQTT纯粹是一种传输，它将携带您给它的任何字节作为有效负载(最大256MB)，并且不会以任何方式更改它们。

如果你想先压缩有效载荷，那完全取决于你。

Answer 2

我为我的UFM (通用文件移动器)开源Java项目创建了一个名为JZIP的包装类。您可以从here下载源代码。

下面就是JZip类。它有两种方法: compressData和decompressData。两者都希望输入为byte[]，并提供byte[]作为输出。它使用起来非常简单。

package com.capitalware.ufm.handlers;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.DataFormatException;
import java.util.zip.Deflater;
import java.util.zip.Inflater;

import com.capitalware.ufm.UFM;

/**
 * This class will handle all of UFM's compression and decompression work.
 * @author Roger Lacroix
 * @version 1.0
 * @license Apache 2 License
 */
public class JZip
{
   /**
    * The constructor - make sure nothing instantiates this class.
    * It must be accessed in a static way.
    */
   private JZip()
   {}

   /**
    * This method will compress a byte array of data.
    *
    * @param inputData an array of bytes
    * @return byte array of the contents of the file.
    */
   public static byte[] compressData(byte[] inputData)
   {
      // Create the compressor with highest level of compression
      Deflater compressor = new Deflater();
      compressor.setLevel(Deflater.BEST_COMPRESSION);

      // Give the compressor the data to compress
      compressor.setInput(inputData);
      compressor.finish();

      // Create an expandable byte array to hold the compressed data.
      // You cannot use an array that's the same size as the orginal because
      // there is no guarantee that the compressed data will be smaller than
      // the uncompressed data.
      ByteArrayOutputStream bos = new ByteArrayOutputStream(inputData.length);

      // Compress the data
      byte[] buf = new byte[65536];
      while (!compressor.finished())
      {
         int count = compressor.deflate(buf);
         bos.write(buf, 0, count);
      }
      try
      {
         bos.close();
      }
      catch (IOException e)
      {
         UFM.logger.fatal("IOException: " + e.getLocalizedMessage());
      }

      // return compressed data
      return bos.toByteArray();
   }

   /**
    * This method will decompress a byte array of compressed data.
    *
    * @param compressedData an array of bytes
    * @return byte array of uncompressed data
    */
   public static byte[] decompressData(byte[] compressedData)
   {
      // Create the decompressor and give it the data to compress
      Inflater decompressor = new Inflater();
      decompressor.setInput(compressedData);

      // Create an expandable byte array to hold the decompressed data
      ByteArrayOutputStream bos = new ByteArrayOutputStream(compressedData.length);

      // Decompress the data
      byte[] buf = new byte[65536];
      while (!decompressor.finished())
      {
         try
         {
            int count = decompressor.inflate(buf);
            bos.write(buf, 0, count);
         }
         catch (DataFormatException e)
         {
            UFM.logger.fatal("DataFormatException: " + e.getLocalizedMessage());
         }
      }
      try
      {
         bos.close();
      }
      catch (IOException e)
      {
         UFM.logger.fatal("IOException: " + e.getLocalizedMessage());
      }

      // return uncompressed data
      return bos.toByteArray();
   }
}