io.netty.handler.codec

Class LengthFieldPrepender

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

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

io.netty.handler.codec.LengthFieldPrepender

All Implemented Interfaces:

ChannelHandler

@ChannelHandler.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 io.netty.channel.ChannelHandler

ChannelHandler.Sharable, ChannelHandler.Skip

Constructor Summary

Constructors

Constructor and 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.

Method Summary

Methods

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

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

acceptOutboundMessage, write

Methods inherited from class io.netty.channel.ChannelHandlerAdapter

bind, channelActive, channelInactive, channelRead, channelReadComplete, channelRegistered, channelUnregistered, channelWritabilityChanged, close, connect, deregister, disconnect, exceptionCaught, flush, handlerAdded, handlerRemoved, isSharable, read, userEventTriggered

Methods inherited from class java.lang.Object

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

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

Method Detail

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 aggragation

Throws:

Exception - is thrown if an error accour