Package io.netty.handler.codec

Class LengthFieldPrepender

  • All Implemented Interfaces:
    io.netty.channel.ChannelHandler, io.netty.channel.ChannelOutboundHandler
    @Sharable
public class LengthFieldPrepender
extends MessageToMessageEncoder<io.netty.buffer.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" |
 +--------+----------------+

    • Nested Class Summary

      • Nested classes/interfaces inherited from interface io.netty.channel.ChannelHandler

        io.netty.channel.ChannelHandler.Sharable

    • Constructor Summary

      Constructors 
      Constructor Description
      LengthFieldPrepender​(int lengthFieldLength)
      Creates a new instance.
      LengthFieldPrepender​(int lengthFieldLength, boolean lengthIncludesLengthFieldLength)
      Creates a new instance.
      LengthFieldPrepender​(int lengthFieldLength, int lengthAdjustment)
      Creates a new instance.
      LengthFieldPrepender​(int lengthFieldLength, int lengthAdjustment, boolean lengthIncludesLengthFieldLength)
      Creates a new instance.
      LengthFieldPrepender​(ByteOrder byteOrder, int lengthFieldLength, int lengthAdjustment, boolean lengthIncludesLengthFieldLength)
      Creates a new instance.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      protected void encode​(io.netty.channel.ChannelHandlerContext ctx, io.netty.buffer.ByteBuf msg, List<Object> out)
      Encode from one message to an other.

      • Methods inherited from class io.netty.channel.ChannelOutboundHandlerAdapter

        bind, close, connect, deregister, disconnect, flush, read

      • Methods inherited from class io.netty.channel.ChannelHandlerAdapter

        ensureNotSharable, exceptionCaught, handlerAdded, handlerRemoved, isSharable

      • Methods inherited from interface io.netty.channel.ChannelHandler

        exceptionCaught, handlerAdded, handlerRemoved

    • 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:
        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:
        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:
        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:
        IllegalArgumentException - if lengthFieldLength is not 1, 2, 3, 4, or 8

      • LengthFieldPrepender

        public LengthFieldPrepender​(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:
        IllegalArgumentException - if lengthFieldLength is not 1, 2, 3, 4, or 8

    • Method Detail

      • encode

        protected void encode​(io.netty.channel.ChannelHandlerContext ctx,
                      io.netty.buffer.ByteBuf msg,
                      List<Object> out)
               throws 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<io.netty.buffer.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:
        Exception - is thrown if an error occurs