Class LengthFieldPrepender

  • All Implemented Interfaces:
    ChannelHandler, ChannelOutboundHandler

    @Sharable
    public class LengthFieldPrepender
    extends MessageToMessageEncoder<ByteBuf>
    An encoder that prepends the length of the message. The length value is prepended as a binary form.

    For example, LengthFieldPrepender(2) will encode the following 12-bytes string:

     +----------------+
     | "HELLO, WORLD" |
     +----------------+
     
    into the following:
     +--------+----------------+
     + 0x000C | "HELLO, WORLD" |
     +--------+----------------+
     
    If you turned on the lengthIncludesLengthFieldLength flag in the constructor, the encoded data would look like the following (12 (original data) + 2 (prepended data) = 14 (0xE)):
     +--------+----------------+
     + 0x000E | "HELLO, WORLD" |
     +--------+----------------+
     
    • Constructor Detail

      • LengthFieldPrepender

        public LengthFieldPrepender​(int lengthFieldLength)
        Creates a new instance.
        Parameters:
        lengthFieldLength - the length of the prepended length field. Only 1, 2, 3, 4, and 8 are allowed.
        Throws:
        java.lang.IllegalArgumentException - if lengthFieldLength is not 1, 2, 3, 4, or 8
      • LengthFieldPrepender

        public LengthFieldPrepender​(int lengthFieldLength,
                                    boolean lengthIncludesLengthFieldLength)
        Creates a new instance.
        Parameters:
        lengthFieldLength - the length of the prepended length field. Only 1, 2, 3, 4, and 8 are allowed.
        lengthIncludesLengthFieldLength - if true, the length of the prepended length field is added to the value of the prepended length field.
        Throws:
        java.lang.IllegalArgumentException - if lengthFieldLength is not 1, 2, 3, 4, or 8
      • LengthFieldPrepender

        public LengthFieldPrepender​(int lengthFieldLength,
                                    int lengthAdjustment)
        Creates a new instance.
        Parameters:
        lengthFieldLength - the length of the prepended length field. Only 1, 2, 3, 4, and 8 are allowed.
        lengthAdjustment - the compensation value to add to the value of the length field
        Throws:
        java.lang.IllegalArgumentException - if lengthFieldLength is not 1, 2, 3, 4, or 8
      • LengthFieldPrepender

        public LengthFieldPrepender​(int lengthFieldLength,
                                    int lengthAdjustment,
                                    boolean lengthIncludesLengthFieldLength)
        Creates a new instance.
        Parameters:
        lengthFieldLength - the length of the prepended length field. Only 1, 2, 3, 4, and 8 are allowed.
        lengthAdjustment - the compensation value to add to the value of the length field
        lengthIncludesLengthFieldLength - if true, the length of the prepended length field is added to the value of the prepended length field.
        Throws:
        java.lang.IllegalArgumentException - if lengthFieldLength is not 1, 2, 3, 4, or 8
      • LengthFieldPrepender

        public LengthFieldPrepender​(java.nio.ByteOrder byteOrder,
                                    int lengthFieldLength,
                                    int lengthAdjustment,
                                    boolean lengthIncludesLengthFieldLength)
        Creates a new instance.
        Parameters:
        byteOrder - the ByteOrder of the length field
        lengthFieldLength - the length of the prepended length field. Only 1, 2, 3, 4, and 8 are allowed.
        lengthAdjustment - the compensation value to add to the value of the length field
        lengthIncludesLengthFieldLength - if true, the length of the prepended length field is added to the value of the prepended length field.
        Throws:
        java.lang.IllegalArgumentException - if lengthFieldLength is not 1, 2, 3, 4, or 8
    • Method Detail

      • encode

        protected void encode​(ChannelHandlerContext ctx,
                              ByteBuf msg,
                              java.util.List<java.lang.Object> out)
                       throws java.lang.Exception
        Description copied from class: MessageToMessageEncoder
        Encode from one message to an other. This method will be called for each written message that can be handled by this encoder.
        Specified by:
        encode in class MessageToMessageEncoder<ByteBuf>
        Parameters:
        ctx - the ChannelHandlerContext which this MessageToMessageEncoder belongs to
        msg - the message to encode to an other one
        out - the List into which the encoded msg should be added needs to do some kind of aggregation
        Throws:
        java.lang.Exception - is thrown if an error occurs