Class CompressionFilter

  • All Implemented Interfaces:
    IoFilter

    public class CompressionFilter
    extends WriteRequestFilter
    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.

    Author:
    Apache MINA Project
    • Field Detail

      • 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:
        Constant Field Values
      • COMPRESSION_MIN

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

        public static final int COMPRESSION_NONE
        No compression done on the data.
        See Also:
        Constant Field Values
      • COMPRESSION_DEFAULT

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

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

      • 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 Detail

      • 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