Package 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:

ChannelHandler, ChannelInboundHandler

Direct Known Subclasses:

Base64Decoder, ByteArrayDecoder, DatagramDnsQueryDecoder, DatagramDnsResponseDecoder, DatagramPacketDecoder, HttpContentDecoder, MessageAggregator, RedisArrayAggregator, SctpInboundByteStreamHandler, SctpMessageCompletionHandler, SctpMessageToMessageDecoder, SpdyHttpDecoder, StringDecoder, WebSocketExtensionDecoder, WebSocketProtocolHandler

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 io.netty.channel.ChannelHandler

ChannelHandler.Sharable

Field Summary

Fields

Modifier and Type	Field	Description
private boolean	decodeCalled
private final TypeParameterMatcher	matcher
private boolean	messageProduced

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 io.netty.channel.ChannelInboundHandlerAdapter

channelActive, channelInactive, 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

Field Details

matcher

private final TypeParameterMatcher matcher

decodeCalled

private boolean decodeCalled

messageProduced

private boolean messageProduced

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