Class DelimiterBasedFrameDecoder

java.lang.Object
io.netty.channel.ChannelHandlerAdapter
io.netty.channel.ChannelInboundHandlerAdapter
io.netty.handler.codec.ByteToMessageDecoder
io.netty.handler.codec.DelimiterBasedFrameDecoder
All Implemented Interfaces:
ChannelHandler, ChannelInboundHandler
public class DelimiterBasedFrameDecoder extends ByteToMessageDecoder
A decoder that splits the received ByteBufs by one or more delimiters. It is particularly useful for decoding the frames which ends with a delimiter such as NUL or newline characters.

Predefined delimiters

Delimiters defines frequently used delimiters for convenience' sake.

Specifying more than one delimiter

DelimiterBasedFrameDecoder allows you to specify more than one delimiter. If more than one delimiter is found in the buffer, it chooses the delimiter which produces the shortest frame. For example, if you have the following data in the buffer: 

+--------------+
| ABC\nDEF\r\n |
+--------------+
a DelimiterBasedFrameDecoder(Delimiters.lineDelimiter()) will choose '\n' as the first delimiter and produce two frames: 
+-----+-----+
| ABC | DEF |
+-----+-----+
rather than incorrectly choosing '\r\n' as the first delimiter: 
+----------+
| ABC\nDEF |
+----------+

  • Field Details

    • INITIAL_SCAN_WINDOW

      private static final int INITIAL_SCAN_WINDOW
      Size of the first window searched when more than one delimiter is configured.
      See Also:

    • delimiters

      private final ByteBuf[] delimiters

    • maxDelimiterLength

      private final int maxDelimiterLength

    • maxFrameLength

      private final int maxFrameLength

    • stripDelimiter

      private final boolean stripDelimiter

    • failFast

      private final boolean failFast

    • discardingTooLongFrame

      private boolean discardingTooLongFrame

    • tooLongFrameLength

      private int tooLongFrameLength

    • lineBasedDecoder

      private final LineBasedFrameDecoder lineBasedDecoder
      Set only when decoding with "\n" and "\r\n" as the delimiter.

    • scanOffset

      private int scanOffset
      Last scan position, relative to the reader index, at which no delimiter could be found. Resuming from this offset avoids rescanning the whole buffer from the reader index on every decode(ChannelHandlerContext, ByteBuf) call.

  • Constructor Details

    • DelimiterBasedFrameDecoder

      public DelimiterBasedFrameDecoder(int maxFrameLength, ByteBuf delimiter)
      Creates a new instance.
      Parameters:
      maxFrameLength - the maximum length of the decoded frame. A TooLongFrameException is thrown if the length of the frame exceeds this value.
      delimiter - the delimiter

    • DelimiterBasedFrameDecoder

      public DelimiterBasedFrameDecoder(int maxFrameLength, boolean stripDelimiter, ByteBuf delimiter)
      Creates a new instance.
      Parameters:
      maxFrameLength - the maximum length of the decoded frame. A TooLongFrameException is thrown if the length of the frame exceeds this value.
      stripDelimiter - whether the decoded frame should strip out the delimiter or not
      delimiter - the delimiter

    • DelimiterBasedFrameDecoder

      public DelimiterBasedFrameDecoder(int maxFrameLength, boolean stripDelimiter, boolean failFast, ByteBuf delimiter)
      Creates a new instance.
      Parameters:
      maxFrameLength - the maximum length of the decoded frame. A TooLongFrameException is thrown if the length of the frame exceeds this value.
      stripDelimiter - whether the decoded frame should strip out the delimiter or not
      failFast - If true, a TooLongFrameException is thrown as soon as the decoder notices the length of the frame will exceed maxFrameLength regardless of whether the entire frame has been read. If false, a TooLongFrameException is thrown after the entire frame that exceeds maxFrameLength has been read.
      delimiter - the delimiter

    • DelimiterBasedFrameDecoder

      public DelimiterBasedFrameDecoder(int maxFrameLength, ByteBuf... delimiters)
      Creates a new instance.
      Parameters:
      maxFrameLength - the maximum length of the decoded frame. A TooLongFrameException is thrown if the length of the frame exceeds this value.
      delimiters - the delimiters

    • DelimiterBasedFrameDecoder

      public DelimiterBasedFrameDecoder(int maxFrameLength, boolean stripDelimiter, ByteBuf... delimiters)
      Creates a new instance.
      Parameters:
      maxFrameLength - the maximum length of the decoded frame. A TooLongFrameException is thrown if the length of the frame exceeds this value.
      stripDelimiter - whether the decoded frame should strip out the delimiter or not
      delimiters - the delimiters

    • DelimiterBasedFrameDecoder

      public DelimiterBasedFrameDecoder(int maxFrameLength, boolean stripDelimiter, boolean failFast, ByteBuf... delimiters)
      Creates a new instance.
      Parameters:
      maxFrameLength - the maximum length of the decoded frame. A TooLongFrameException is thrown if the length of the frame exceeds this value.
      stripDelimiter - whether the decoded frame should strip out the delimiter or not
      failFast - If true, a TooLongFrameException is thrown as soon as the decoder notices the length of the frame will exceed maxFrameLength regardless of whether the entire frame has been read. If false, a TooLongFrameException is thrown after the entire frame that exceeds maxFrameLength has been read.
      delimiters - the delimiters

  • Method Details

    • isLineBased

      private static boolean isLineBased(ByteBuf[] delimiters)
      Returns true if the delimiters are "\n" and "\r\n".

    • isSubclass

      private boolean isSubclass()
      Return true if the current instance is a subclass of DelimiterBasedFrameDecoder

    • decode

      protected final void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception
      Description copied from class: ByteToMessageDecoder
      Decode the from one ByteBuf to an other. This method will be called till either the input ByteBuf has nothing to read when return from this method or till nothing was read from the input ByteBuf.
      Specified by:
      decode in class ByteToMessageDecoder
      Parameters:
      ctx - the ChannelHandlerContext which this ByteToMessageDecoder belongs to
      in - the ByteBuf from which to read data
      out - the List to which decoded messages should be added
      Throws:
      Exception - is thrown if an error occurs

    • decode

      protected Object decode(ChannelHandlerContext ctx, ByteBuf buffer) throws Exception
      Create a frame out of the ByteBuf and return it.
      Parameters:
      ctx - the ChannelHandlerContext which this ByteToMessageDecoder belongs to
      buffer - the ByteBuf from which to read data
      Returns:
      frame the ByteBuf which represent the frame or null if no frame could be created.
      Throws:
      Exception

    • partialDelimiterLength

      private int partialDelimiterLength(ByteBuf buffer)
      Returns the length of the longest suffix of the readable bytes that is the beginning of a delimiter.

    • fail

      private void fail(long frameLength)

    • validateDelimiter

      private static void validateDelimiter(ByteBuf delimiter)

    • validateMaxFrameLength

      private static void validateMaxFrameLength(int maxFrameLength)