Class CompressionFilter

java.lang.Object
org.apache.mina.core.filterchain.IoFilterAdapter
org.apache.mina.filter.compression.CompressionFilter
All Implemented Interfaces:
IoFilter
public class CompressionFilter extends IoFilterAdapter
An IoFilter which compresses all data using JZlib. Support for the LZW (DLCZ) algorithm is also planned.

This filter only supports compression using the PARTIAL FLUSH method, since that is the only method useful when doing stream level compression.

This filter supports compression/decompression of the input and output channels selectively. It can also be enabled/disabled on the fly.

This filter does not discard the zlib objects, keeping them around for the entire life of the filter. This is because the zlib dictionary needs to be built up over time, which is used during compression and decompression. Over time, as repetitive data is sent over the wire, the compression efficiency steadily increases.

Note that the zlib header is written only once. It is not necessary that the data received after processing by this filter may not be complete due to packet fragmentation.

It goes without saying that the other end of this stream should also have a compatible compressor/decompressor using the same algorithm.

  • Field Details

    • COMPRESSION_MAX

      public static final int COMPRESSION_MAX
      Max compression level. Will give the highest compression ratio, but will also take more cpu time and is the slowest.
      See Also:

    • COMPRESSION_MIN

      public static final int COMPRESSION_MIN
      Provides the best speed at the price of a low compression ratio.
      See Also:

    • COMPRESSION_NONE

      public static final int COMPRESSION_NONE
      No compression done on the data.
      See Also:

    • COMPRESSION_DEFAULT

      public static final int COMPRESSION_DEFAULT
      The default compression level used. Provides the best balance between speed and compression
      See Also:

    • DEFLATER

      private final AttributeKey DEFLATER
      A session attribute that stores the Zlib object used for compression.

    • INFLATER

      private final AttributeKey INFLATER
      A session attribute that stores the Zlib object used for decompression.

    • DISABLE_COMPRESSION_ONCE

      public static final AttributeKey DISABLE_COMPRESSION_ONCE
      A flag that allows you to disable compression once.

    • compressInbound

      private boolean compressInbound

    • compressOutbound

      private boolean compressOutbound

    • compressionLevel

      private int compressionLevel

  • Constructor Details

    • CompressionFilter

      public CompressionFilter()
      Creates a new instance which compresses outboud data and decompresses inbound data with default compression level.

    • CompressionFilter

      public CompressionFilter(int compressionLevel)
      Creates a new instance which compresses outboud data and decompresses inbound data with the specified compressionLevel.
      Parameters:
      compressionLevel - the level of compression to be used. Must be one of COMPRESSION_DEFAULT, COMPRESSION_MAX, COMPRESSION_MIN, and COMPRESSION_NONE.

    • CompressionFilter

      public CompressionFilter(boolean compressInbound, boolean compressOutbound, int compressionLevel)
      Creates a new instance.
      Parameters:
      compressInbound - true if data read is to be decompressed
      compressOutbound - true if data written is to be compressed
      compressionLevel - the level of compression to be used. Must be one of COMPRESSION_DEFAULT, COMPRESSION_MAX, COMPRESSION_MIN, and COMPRESSION_NONE.

  • Method Details

    • filterWrite

      public void filterWrite(IoFilter.NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception
      Filters IoSession.write(Object) method invocation.
      Specified by:
      filterWrite in interface IoFilter
      Overrides:
      filterWrite in class IoFilterAdapter
      Parameters:
      nextFilter - the IoFilter.NextFilter for this filter. You can reuse this object until this filter is removed from the chain.
      session - The IoSession which has to process this invocation
      writeRequest - The WriteRequest to process
      Throws:
      Exception - If an error occurred while processing the event

    • messageReceived

      public void messageReceived(IoFilter.NextFilter nextFilter, IoSession session, Object message) throws Exception
      Description copied from class: IoFilterAdapter
      Filters IoHandler.messageReceived(IoSession,Object) event.
      Specified by:
      messageReceived in interface IoFilter
      Overrides:
      messageReceived in class IoFilterAdapter
      Parameters:
      nextFilter - the IoFilter.NextFilter for this filter. You can reuse this object until this filter is removed from the chain.
      session - The IoSession which has received this event
      message - The received message
      Throws:
      Exception - If an error occurred while processing the event

    • doFilterWrite

      protected Object doFilterWrite(IoFilter.NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws IOException
      Throws:
      IOException

    • onPreAdd

      public void onPreAdd(IoFilterChain parent, String name, IoFilter.NextFilter nextFilter) throws Exception
      Description copied from class: IoFilterAdapter
      Invoked before this filter is added to the specified parent. Please note that this method can be invoked more than once if this filter is added to more than one parents. This method is not invoked before IoFilter.init() is invoked.
      Specified by:
      onPreAdd in interface IoFilter
      Overrides:
      onPreAdd in class IoFilterAdapter
      Parameters:
      parent - the parent who called this method
      name - the name assigned to this filter
      nextFilter - the IoFilter.NextFilter for this filter. You can reuse this object until this filter is removed from the chain.
      Throws:
      Exception - If an error occurred while processing the event

    • isCompressInbound

      public boolean isCompressInbound()
      Returns:
      true if incoming data is being compressed.

    • setCompressInbound

      public void setCompressInbound(boolean compressInbound)
      Sets if incoming data has to be compressed.
      Parameters:
      compressInbound - true if the incoming data has to be compressed

    • isCompressOutbound

      public boolean isCompressOutbound()
      Returns:
      true if the filter is compressing data being written.

    • setCompressOutbound

      public void setCompressOutbound(boolean compressOutbound)
      Set if outgoing data has to be compressed.
      Parameters:
      compressOutbound - true if the outgoing data has to be compressed

    • onPostRemove

      public void onPostRemove(IoFilterChain parent, String name, IoFilter.NextFilter nextFilter) throws Exception
      Description copied from class: IoFilterAdapter
      Invoked after this filter is removed from the specified parent. Please note that this method can be invoked more than once if this filter is removed from more than one parents. This method is always invoked before IoFilter.destroy() is invoked.
      Specified by:
      onPostRemove in interface IoFilter
      Overrides:
      onPostRemove in class IoFilterAdapter
      Parameters:
      parent - the parent who called this method
      name - the name assigned to this filter
      nextFilter - the IoFilter.NextFilter for this filter. You can reuse this object until this filter is removed from the chain.
      Throws:
      Exception - If an error occurred while processing the event