io.netty.handler.codec

Class MessageToMessageDecoder<I>

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

io.netty.channel.ChannelInboundHandlerAdapter

io.netty.handler.codec.MessageToMessageDecoder<I>

All Implemented Interfaces:

io.netty.channel.ChannelHandler, io.netty.channel.ChannelInboundHandler

Direct Known Subclasses:

Base64Decoder, ByteArrayDecoder, DatagramPacketDecoder, MessageAggregator, ProtobufDecoder, ProtobufDecoderNano, StringDecoder

public abstract class MessageToMessageDecoder<I>
extends io.netty.channel.ChannelInboundHandlerAdapter

ChannelInboundHandlerAdapter which decodes from one message to an other message. For example here is an implementation which decodes a String to an Integer which represent the length of the String.

     public class StringToIntegerDecoder extends
             MessageToMessageDecoder<String> {

          @Override
         public void decode(ChannelHandlerContext ctx, String message,
                            List<Object> out) throws Exception {
             out.add(message.length());
         }
     }
 

Be aware that you need to call ReferenceCounted.retain() on messages that are just passed through if they are of type ReferenceCounted. This is needed as the MessageToMessageDecoder will call ReferenceCounted.release() on decoded messages.

Nested Class Summary

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

io.netty.channel.ChannelHandler.Sharable

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	MessageToMessageDecoder() Create a new instance which will try to detect the types to match out of the type parameter of the class.
protected	MessageToMessageDecoder(Class<? extends I> inboundMessageType) Create a new instance

Method Summary

Modifier and Type	Method and Description
boolean	acceptInboundMessage(Object msg) Returns true if the given message should be handled.
void	channelRead(io.netty.channel.ChannelHandlerContext ctx, Object msg)
protected abstract void	decode(io.netty.channel.ChannelHandlerContext ctx, I msg, List<Object> out) Decode from one message to an other.

Methods inherited from class io.netty.channel.ChannelInboundHandlerAdapter

channelActive, channelInactive, channelReadComplete, channelRegistered, channelUnregistered, channelWritabilityChanged, exceptionCaught, userEventTriggered

Methods inherited from class io.netty.channel.ChannelHandlerAdapter

ensureNotSharable, handlerAdded, handlerRemoved, 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, handlerRemoved

Constructor Detail

MessageToMessageDecoder

protected MessageToMessageDecoder()

Create a new instance which will try to detect the types to match out of the type parameter of the class.

MessageToMessageDecoder

protected MessageToMessageDecoder(Class<? extends I> inboundMessageType)

Create a new instance

Parameters:

inboundMessageType - The type of messages to match and so decode

Method Detail

acceptInboundMessage

public boolean acceptInboundMessage(Object msg)
                             throws Exception

Returns true if the given message should be handled. If false it will be passed to the next ChannelInboundHandler in the ChannelPipeline.

Throws:

Exception

channelRead

public void channelRead(io.netty.channel.ChannelHandlerContext ctx,
                        Object msg)
                 throws Exception

Specified by:

channelRead in interface io.netty.channel.ChannelInboundHandler

Overrides:

channelRead in class io.netty.channel.ChannelInboundHandlerAdapter

Throws:

Exception

decode

protected abstract void decode(io.netty.channel.ChannelHandlerContext ctx,
                               I msg,
                               List<Object> out)
                        throws Exception

Decode from one message to an other. This method will be called for each written message that can be handled by this decoder.

Parameters:

ctx - the ChannelHandlerContext which this MessageToMessageDecoder belongs to

msg - the message to decode to an other one

out - the List to which decoded messages should be added

Throws:

Exception - is thrown if an error occurs