Class MessageToMessageDecoder<I>

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

io.netty.channel.ChannelInboundHandlerAdapter

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

All Implemented Interfaces:

ChannelHandler, ChannelInboundHandler

Direct Known Subclasses:

Base64Decoder, ByteArrayDecoder, DatagramDnsQueryDecoder, DatagramDnsResponseDecoder, DatagramPacketDecoder, HttpContentDecoder, MessageAggregator, ProtobufDecoder, ProtobufDecoderNano, RedisArrayAggregator, SctpInboundByteStreamHandler, SctpMessageCompletionHandler, SctpMessageToMessageDecoder, SpdyHttpDecoder, StringDecoder, WebSocketClientProtocolHandler, WebSocketExtensionDecoder, WebSocketServerProtocolHandler

public abstract class MessageToMessageDecoder<I>
extends 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 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

Modifier	Constructor	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	Description
boolean	acceptInboundMessage(Object msg)	Returns true if the given message should be handled.
void	channelRead(ChannelHandlerContext ctx, Object msg)	Calls ChannelHandlerContext.fireChannelRead(Object) to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	channelReadComplete(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelReadComplete() to forward to the next ChannelInboundHandler in the ChannelPipeline.
protected abstract void	decode(ChannelHandlerContext ctx, I msg, List<Object> out)	Decode from one message to an other.

Methods inherited from class ChannelInboundHandlerAdapter

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

Modifier and Type	Method	Description
void	channelActive(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelActive() to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	channelInactive(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelInactive() to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	channelRegistered(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelRegistered() to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	channelUnregistered(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelUnregistered() to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	channelWritabilityChanged(ChannelHandlerContext ctx)	Calls ChannelHandlerContext.fireChannelWritabilityChanged() to forward to the next ChannelInboundHandler in the ChannelPipeline.
void	exceptionCaught(ChannelHandlerContext ctx, Throwable cause)	Calls ChannelHandlerContext.fireExceptionCaught(Throwable) to forward to the next ChannelHandler in the ChannelPipeline.
void	userEventTriggered(ChannelHandlerContext ctx, Object evt)	Calls ChannelHandlerContext.fireUserEventTriggered(Object) to forward to the next ChannelInboundHandler in the ChannelPipeline.

Methods inherited from class ChannelHandlerAdapter

ensureNotSharable, handlerAdded, handlerRemoved, isSharable

Modifier and Type	Method	Description
protected void	ensureNotSharable()	Throws IllegalStateException if ChannelHandlerAdapter.isSharable() returns true
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

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 Details

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(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

channelReadComplete

public void channelReadComplete(ChannelHandlerContext ctx)
                         throws Exception

Description copied from class: ChannelInboundHandlerAdapter

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

Specified by:

channelReadComplete in interface ChannelInboundHandler

Overrides:

channelReadComplete in class ChannelInboundHandlerAdapter

Throws:

Exception

decode

protected abstract void decode(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