Class LengthFieldPrepender

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

io.netty.channel.ChannelOutboundHandlerAdapter

io.netty.handler.codec.MessageToMessageEncoder<ByteBuf>

io.netty.handler.codec.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" |
+--------+----------------+

Nested Class Summary

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.

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

Modifier and Type	Method	Description
protected void	encode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out)	Encode from one message to an other.

Methods inherited from class MessageToMessageEncoder

acceptOutboundMessage, write

Modifier and Type	Method	Description
boolean	acceptOutboundMessage(Object msg)	Returns true if the given message should be handled.
void	write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise)	Calls ChannelOutboundInvoker.write(Object, ChannelPromise) to forward to the next ChannelOutboundHandler in the ChannelPipeline.

Methods inherited from class ChannelOutboundHandlerAdapter

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

Modifier and Type	Method	Description
void	bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise)	Calls ChannelOutboundInvoker.bind(SocketAddress, ChannelPromise) to forward to the next ChannelOutboundHandler in the ChannelPipeline.
void	close(ChannelHandlerContext ctx, ChannelPromise promise)	Calls ChannelOutboundInvoker.close(ChannelPromise) to forward to the next ChannelOutboundHandler in the ChannelPipeline.
void	connect(ChannelHandlerContext ctx, SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise)	Calls ChannelOutboundInvoker.connect(SocketAddress, SocketAddress, ChannelPromise) to forward to the next ChannelOutboundHandler in the ChannelPipeline.
void	deregister(ChannelHandlerContext ctx, ChannelPromise promise)	Calls ChannelOutboundInvoker.deregister(ChannelPromise) to forward to the next ChannelOutboundHandler in the ChannelPipeline.
void	disconnect(ChannelHandlerContext ctx, ChannelPromise promise)	Calls ChannelOutboundInvoker.disconnect(ChannelPromise) to forward to the next ChannelOutboundHandler in the ChannelPipeline.
void	flush(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.flush() to forward to the next ChannelOutboundHandler in the ChannelPipeline.
void	read(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.read() to forward to the next ChannelOutboundHandler in the ChannelPipeline.

Methods inherited from class ChannelHandlerAdapter

ensureNotSharable, exceptionCaught, handlerAdded, handlerRemoved, isSharable

Modifier and Type	Method	Description
protected void	ensureNotSharable()	Throws IllegalStateException if ChannelHandlerAdapter.isSharable() returns true
void	exceptionCaught(ChannelHandlerContext ctx, Throwable cause)	Deprecated. is part of ChannelInboundHandler
void	handlerAdded(ChannelHandlerContext ctx)	Do nothing by default, sub-classes may override this method.
void	handlerRemoved(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

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 Details

encode

protected void encode(ChannelHandlerContext ctx,
 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<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