io.netty.handler.codec

Class MessageToMessageCodec<INBOUND_IN,OUTBOUND_IN>

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

io.netty.channel.ChannelInboundHandlerAdapter

io.netty.channel.ChannelDuplexHandler

io.netty.handler.codec.MessageToMessageCodec<INBOUND_IN,OUTBOUND_IN>

All Implemented Interfaces:

ChannelHandler, ChannelInboundHandler, ChannelOutboundHandler

Direct Known Subclasses:

Http2StreamFrameToHttpObjectCodec, HttpContentEncoder, SpdyHttpResponseStreamIdHandler

public abstract class MessageToMessageCodec<INBOUND_IN,OUTBOUND_IN>
extends ChannelDuplexHandler

A Codec for on-the-fly encoding/decoding of message. This can be thought of as a combination of MessageToMessageDecoder and MessageToMessageEncoder. Here is an example of a MessageToMessageCodec which just decode from Integer to Long and encode from Long to Integer.

     public class NumberCodec extends
             MessageToMessageCodec<Integer, Long> {
          @Override
         public Long decode(ChannelHandlerContext ctx, Integer msg, List<Object> out)
                 throws Exception {
             out.add(msg.longValue());
         }

          @Override
         public Integer encode(ChannelHandlerContext ctx, Long msg, List<Object> out)
                 throws Exception {
             out.add(msg.intValue());
         }
     }
 

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 MessageToMessageCodec will call ReferenceCounted.release() on encoded / decoded messages.

Nested Class Summary

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

ChannelHandler.Sharable

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	MessageToMessageCodec() Create a new instance which will try to detect the types to decode and encode out of the type parameter of the class.
protected	MessageToMessageCodec(Class<? extends INBOUND_IN> inboundMessageType, Class<? extends OUTBOUND_IN> outboundMessageType) Create a new instance.

Method Summary

Modifier and Type	Method and Description
boolean	acceptInboundMessage(Object msg) Returns true if and only if the specified message can be decoded by this codec.
boolean	acceptOutboundMessage(Object msg) Returns true if and only if the specified message can be encoded by this codec.
void	channelRead(ChannelHandlerContext ctx, Object msg) Calls ChannelHandlerContext.fireChannelRead(Object) to forward to the next ChannelInboundHandler in the ChannelPipeline.
protected abstract void	decode(ChannelHandlerContext ctx, INBOUND_IN msg, List<Object> out)
protected abstract void	encode(ChannelHandlerContext ctx, OUTBOUND_IN msg, List<Object> out)
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 io.netty.channel.ChannelDuplexHandler

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

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

exceptionCaught, handlerAdded, handlerRemoved

Constructor Detail

MessageToMessageCodec

protected MessageToMessageCodec()

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

MessageToMessageCodec

protected MessageToMessageCodec(Class<? extends INBOUND_IN> inboundMessageType,
                                Class<? extends OUTBOUND_IN> outboundMessageType)

Create a new instance.

Parameters:

inboundMessageType - The type of messages to decode

outboundMessageType - The type of messages to encode

Method Detail

channelRead

public void channelRead(ChannelHandlerContext ctx,
                        Object msg)
                 throws Exception

Description copied from class: ChannelInboundHandlerAdapter

Calls ChannelHandlerContext.fireChannelRead(Object) to forward to the next ChannelInboundHandler in the ChannelPipeline. Sub-classes may override this method to change behavior.

Specified by:

channelRead in interface ChannelInboundHandler

Overrides:

channelRead in class ChannelInboundHandlerAdapter

Throws:

Exception

write

public void write(ChannelHandlerContext ctx,
                  Object msg,
                  ChannelPromise promise)
           throws Exception

Description copied from class: ChannelDuplexHandler

Calls ChannelOutboundInvoker.write(Object, ChannelPromise) to forward to the next ChannelOutboundHandler in the ChannelPipeline. Sub-classes may override this method to change behavior.

Specified by:

write in interface ChannelOutboundHandler

Overrides:

write in class ChannelDuplexHandler

Parameters:

ctx - the ChannelHandlerContext for which the write operation is made

msg - the message to write

promise - the ChannelPromise to notify once the operation completes

Throws:

Exception - thrown if an error occurs

acceptInboundMessage

public boolean acceptInboundMessage(Object msg)
                             throws Exception

Returns true if and only if the specified message can be decoded by this codec.

Parameters:

msg - the message

Throws:

Exception

acceptOutboundMessage

public boolean acceptOutboundMessage(Object msg)
                              throws Exception

Returns true if and only if the specified message can be encoded by this codec.

Parameters:

msg - the message

Throws:

Exception

encode

protected abstract void encode(ChannelHandlerContext ctx,
                               OUTBOUND_IN msg,
                               List<Object> out)
                        throws Exception

Throws:

Exception

See Also:

MessageToMessageEncoder.encode(ChannelHandlerContext, Object, List)

decode

protected abstract void decode(ChannelHandlerContext ctx,
                               INBOUND_IN msg,
                               List<Object> out)
                        throws Exception

Throws:

Exception

See Also:

MessageToMessageDecoder.decode(ChannelHandlerContext, Object, List)