Class LineBasedFrameDecoder

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

io.netty.channel.ChannelInboundHandlerAdapter

io.netty.handler.codec.ByteToMessageDecoder

io.netty.handler.codec.LineBasedFrameDecoder

All Implemented Interfaces:

ChannelHandler, ChannelInboundHandler

Direct Known Subclasses:

SmtpResponseDecoder

public class LineBasedFrameDecoder
extends ByteToMessageDecoder

A decoder that splits the received ByteBufs on line endings.

Both "\n" and "\r\n" are handled.

The byte stream is expected to be in UTF-8 character encoding or ASCII. The current implementation uses direct byte to char cast and then compares that char to a few low range ASCII characters like '\n' or '\r'. UTF-8 is not using low range [0..0x7F] byte values for multibyte codepoint representations therefore fully supported by this implementation.

For a more general delimiter-based decoder, see DelimiterBasedFrameDecoder.

Users should be aware that used as is, the lenient approach on lone '\n might result on a parser diffenrencial on line based protocols requiring the use of "\r\n" delimiters like SMTP and can result in attacks similar to SMTP smuggling. Validating afterward the end of line pattern can be a possible mitigation.

Nested Class Summary

Nested classes/interfaces inherited from class ByteToMessageDecoder

ByteToMessageDecoder.Cumulator

Modifier and Type	Class	Description
static interface	ByteToMessageDecoder.Cumulator	Cumulate ByteBufs.

Nested classes/interfaces inherited from interface ChannelHandler

ChannelHandler.Sharable

Modifier and Type	Interface	Description
static @interface	ChannelHandler.Sharable	Indicates that the same instance of the annotated ChannelHandler can be added to one or more ChannelPipelines multiple times without a race condition.

Field Summary

Fields inherited from class ByteToMessageDecoder

COMPOSITE_CUMULATOR, MERGE_CUMULATOR

Modifier and Type	Field	Description
static final ByteToMessageDecoder.Cumulator	COMPOSITE_CUMULATOR	Cumulate ByteBufs by add them to a CompositeByteBuf and so do no memory copy whenever possible.
static final ByteToMessageDecoder.Cumulator	MERGE_CUMULATOR	Cumulate ByteBufs by merge them into one ByteBuf's, using memory copies.

Constructor Summary

Constructors

Constructor	Description
LineBasedFrameDecoder(int maxLength)	Creates a new decoder.
LineBasedFrameDecoder(int maxLength, boolean stripDelimiter, boolean failFast)	Creates a new decoder.

Method Summary

Modifier and Type	Method	Description
protected Object	decode(ChannelHandlerContext ctx, ByteBuf buffer)	Create a frame out of the ByteBuf and return it.
protected final void	decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out)	Decode the from one ByteBuf to an other.

Methods inherited from class ByteToMessageDecoder

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

Modifier and Type	Method	Description
protected int	actualReadableBytes()	Returns the actual number of readable bytes in the internal cumulative buffer of this decoder.
protected void	callDecode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out)	Called once data should be decoded from the given ByteBuf.
void	channelInactive(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelInactive() to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	channelRead(ChannelHandlerContext ctx, Object input)	Calls ChannelHandlerContext.fireChannelRead(Object) to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	channelReadComplete(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelReadComplete() to forward to the next ChannelInboundHandler in the ChannelPipeline.
protected void	decodeLast(ChannelHandlerContext ctx, ByteBuf in, List<Object> out)	Is called one last time when the ChannelHandlerContext goes in-active.
protected final void	discardSomeReadBytes()
final void	handlerRemoved(ChannelHandlerContext ctx)	Do nothing by default, sub-classes may override this method.
protected void	handlerRemoved0(ChannelHandlerContext ctx)	Gets called after the ByteToMessageDecoder was removed from the actual context and it doesn't handle events anymore.
protected ByteBuf	internalBuffer()	Returns the internal cumulative buffer of this decoder.
boolean	isSingleDecode()	If true then only one message is decoded on each ByteToMessageDecoder.channelRead(ChannelHandlerContext, Object) call.
void	setCumulator(ByteToMessageDecoder.Cumulator cumulator)	Set the ByteToMessageDecoder.Cumulator to use for cumulate the received ByteBufs.
void	setDiscardAfterReads(int discardAfterReads)	Set the number of reads after which ByteBuf.discardSomeReadBytes() are called and so free up memory.
void	setSingleDecode(boolean singleDecode)	If set then only one message is decoded on each ByteToMessageDecoder.channelRead(ChannelHandlerContext, Object) call.
void	userEventTriggered(ChannelHandlerContext ctx, Object evt)	Calls ChannelHandlerContext.fireUserEventTriggered(Object) to forward to the next ChannelInboundHandler in the ChannelPipeline.

Methods inherited from class ChannelInboundHandlerAdapter

channelActive, channelRegistered, channelUnregistered, channelWritabilityChanged, exceptionCaught

Modifier and Type	Method	Description
void	channelActive(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelActive() to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	channelRegistered(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelRegistered() to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	channelUnregistered(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelUnregistered() to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	channelWritabilityChanged(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelWritabilityChanged() to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	exceptionCaught(ChannelHandlerContext ctx, Throwable cause)	Calls ChannelHandlerContext.fireExceptionCaught(Throwable) to forward to the next ChannelHandler in the ChannelPipeline.

Methods inherited from class ChannelHandlerAdapter

ensureNotSharable, handlerAdded, isSharable

Modifier and Type	Method	Description
protected void	ensureNotSharable()	Throws IllegalStateException if ChannelHandlerAdapter.isSharable() returns true
void	handlerAdded(ChannelHandlerContext ctx)	Do nothing by default, sub-classes may override this method.
boolean	isSharable()	Return true if the implementation is ChannelHandler.Sharable and so can be added to different ChannelPipelines.

Methods inherited from class Object

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

Constructor Details

LineBasedFrameDecoder

public LineBasedFrameDecoder(int maxLength)

Creates a new decoder.

Parameters:

maxLength - the maximum length of the decoded frame. A TooLongFrameException is thrown if the length of the frame exceeds this value.

LineBasedFrameDecoder

public LineBasedFrameDecoder(int maxLength,
 boolean stripDelimiter,
 boolean failFast)

Creates a new decoder.

Parameters:

maxLength - 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.

Method Details

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