Package io.netty.handler.codec

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 |
 +----------+
 

Nested Class Summary

Nested classes/interfaces inherited from class io.netty.handler.codec.ByteToMessageDecoder

ByteToMessageDecoder.Cumulator

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

ChannelHandler.Sharable

Field Summary

Fields

Modifier and Type	Field	Description
private ByteBuf[]	delimiters
private boolean	discardingTooLongFrame
private boolean	failFast
private static int	INITIAL_SCAN_WINDOW	Size of the first window searched when more than one delimiter is configured.
private LineBasedFrameDecoder	lineBasedDecoder	Set only when decoding with "\n" and "\r\n" as the delimiter.
private int	maxDelimiterLength
private int	maxFrameLength
private int	scanOffset	Last scan position, relative to the reader index, at which no delimiter could be found.
private boolean	stripDelimiter
private int	tooLongFrameLength

Fields inherited from class io.netty.handler.codec.ByteToMessageDecoder

COMPOSITE_CUMULATOR, cumulation, MERGE_CUMULATOR

Constructor Summary

Constructors

Constructor	Description
DelimiterBasedFrameDecoder(int maxFrameLength, boolean stripDelimiter, boolean failFast, ByteBuf delimiter)	Creates a new instance.
DelimiterBasedFrameDecoder(int maxFrameLength, boolean stripDelimiter, boolean failFast, ByteBuf... delimiters)	Creates a new instance.
DelimiterBasedFrameDecoder(int maxFrameLength, boolean stripDelimiter, ByteBuf delimiter)	Creates a new instance.
DelimiterBasedFrameDecoder(int maxFrameLength, boolean stripDelimiter, ByteBuf... delimiters)	Creates a new instance.
DelimiterBasedFrameDecoder(int maxFrameLength, ByteBuf delimiter)	Creates a new instance.
DelimiterBasedFrameDecoder(int maxFrameLength, ByteBuf... delimiters)	Creates a new instance.

Method Summary

Modifier and Type	Method	Description
protected java.lang.Object	decode(ChannelHandlerContext ctx, ByteBuf buffer)	Create a frame out of the ByteBuf and return it.
protected void	decode(ChannelHandlerContext ctx, ByteBuf in, java.util.List<java.lang.Object> out)	Decode the from one ByteBuf to an other.
private void	fail(long frameLength)
private static boolean	isLineBased(ByteBuf[] delimiters)	Returns true if the delimiters are "\n" and "\r\n".
private boolean	isSubclass()	Return true if the current instance is a subclass of DelimiterBasedFrameDecoder
private static void	validateDelimiter(ByteBuf delimiter)
private static void	validateMaxFrameLength(int maxFrameLength)

Methods inherited from class io.netty.handler.codec.ByteToMessageDecoder

actualReadableBytes, callDecode, channelInactive, channelInputClosed, channelRead, channelReadComplete, decodeLast, decodeRemovalReentryProtection, discardSomeReadBytes, expandCumulation, fireChannelRead, fireChannelRead, handlerRemoved, handlerRemoved0, internalBuffer, isSingleDecode, setCumulator, setDiscardAfterReads, setSingleDecode, userEventTriggered

Methods inherited from class io.netty.channel.ChannelInboundHandlerAdapter

channelActive, channelRegistered, channelUnregistered, channelWritabilityChanged, exceptionCaught

Methods inherited from class io.netty.channel.ChannelHandlerAdapter

ensureNotSharable, handlerAdded, isSharable

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface io.netty.channel.ChannelHandler

handlerAdded

Field Detail

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:

Constant Field Values

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 Detail

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 Detail

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,
                            java.util.List<java.lang.Object> out)
                     throws java.lang.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:

java.lang.Exception - is thrown if an error occurs

decode

protected java.lang.Object decode(ChannelHandlerContext ctx,
                                  ByteBuf buffer)
                           throws java.lang.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:

java.lang.Exception

fail

private void fail(long frameLength)

validateDelimiter

private static void validateDelimiter(ByteBuf delimiter)

validateMaxFrameLength

private static void validateMaxFrameLength(int maxFrameLength)