io.netty.handler.codec

Class LengthFieldPrepender

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

io.netty.channel.ChannelOperationHandlerAdapter

io.netty.channel.ChannelOutboundMessageHandlerAdapter<I>

io.netty.handler.codec.MessageToByteEncoder<io.netty.buffer.ByteBuf>

io.netty.handler.codec.LengthFieldPrepender

All Implemented Interfaces:

io.netty.channel.ChannelHandler, io.netty.channel.ChannelHandlerUtil.SingleOutboundMessageHandler<io.netty.buffer.ByteBuf>, io.netty.channel.ChannelOperationHandler, io.netty.channel.ChannelOutboundMessageHandler<io.netty.buffer.ByteBuf>

@ChannelHandler.Sharable
public class LengthFieldPrepender
extends MessageToByteEncoder<io.netty.buffer.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

io.netty.channel.ChannelHandler.Sharable

Field Summary

Fields inherited from class io.netty.channel.ChannelOutboundMessageHandlerAdapter

ABORT

Constructor Summary

Constructors

Constructor and Description
LengthFieldPrepender(int lengthFieldLength) Creates a new instance.
LengthFieldPrepender(int lengthFieldLength, boolean lengthIncludesLengthFieldLength) Creates a new instance.

Method Summary

Methods

Modifier and Type	Method and Description
protected void	encode(io.netty.channel.ChannelHandlerContext ctx, io.netty.buffer.ByteBuf msg, io.netty.buffer.ByteBuf out) Encode a message into a ByteBuf.

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

flush

Methods inherited from class io.netty.channel.ChannelOutboundMessageHandlerAdapter

acceptOutboundMessage, beginFlush, endFlush, flush, isCloseOnFailedFlush, newOutboundBuffer, setCloseOnFailedFlush

Methods inherited from class io.netty.channel.ChannelOperationHandlerAdapter

bind, close, connect, deregister, disconnect, read, sendFile

Methods inherited from class io.netty.channel.ChannelHandlerAdapter

exceptionCaught, handlerAdded, handlerRemoved

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.ChannelOperationHandler

bind, close, connect, deregister, disconnect, read, sendFile

Methods inherited from interface io.netty.channel.ChannelHandler

exceptionCaught, handlerAdded, handlerRemoved

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

Method Detail

encode

protected void encode(io.netty.channel.ChannelHandlerContext ctx,
          io.netty.buffer.ByteBuf msg,
          io.netty.buffer.ByteBuf out)
               throws Exception

Description copied from class: MessageToByteEncoder

Encode a message into a ByteBuf. This method will be called till the MessageBuf has nothing left.

Specified by:

encode in class MessageToByteEncoder<io.netty.buffer.ByteBuf>

Parameters:

ctx - the ChannelHandlerContext which this MessageToByteEncoder belongs to

msg - the message to encode

out - the ByteBuf into which the encoded message will be written

Throws:

Exception - is thrown if an error accour