io.netty.handler.codec

Class MessageToMessageEncoder<I>

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

io.netty.channel.ChannelOutboundHandlerAdapter

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

All Implemented Interfaces:

ChannelHandler, ChannelOutboundHandler

Direct Known Subclasses:

AbstractMemcacheObjectEncoder, Base64Encoder, ByteArrayEncoder, DatagramDnsQueryEncoder, DatagramDnsResponseEncoder, DatagramPacketEncoder, HttpObjectEncoder, LengthFieldPrepender, LineEncoder, MqttEncoder, ProtobufEncoder, ProtobufEncoderNano, RedisEncoder, SctpOutboundByteStreamHandler, SmtpRequestEncoder, SpdyHttpEncoder, StompSubframeEncoder, StringEncoder, WebSocket00FrameEncoder, WebSocket08FrameEncoder, WebSocketExtensionEncoder

public abstract class MessageToMessageEncoder<I>
extends ChannelOutboundHandlerAdapter

ChannelOutboundHandlerAdapter which encodes from one message to an other message For example here is an implementation which decodes an Integer to an String.

     public class IntegerToStringEncoder extends
             MessageToMessageEncoder<Integer> {

          @Override
         public void encode(ChannelHandlerContext ctx, Integer message, List<Object> out)
                 throws Exception {
             out.add(message.toString());
         }
     }
 

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 MessageToMessageEncoder will call ReferenceCounted.release() on encoded messages.

Nested Class Summary

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

ChannelHandler.Sharable

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
boolean	acceptOutboundMessage(Object msg) Returns true if the given message should be handled.
protected abstract void	encode(ChannelHandlerContext ctx, I msg, List<Object> out) Encode from one message to an other.
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.ChannelOutboundHandlerAdapter

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

Methods inherited from class io.netty.channel.ChannelHandlerAdapter

ensureNotSharable, exceptionCaught, 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

MessageToMessageEncoder

protected MessageToMessageEncoder()

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

MessageToMessageEncoder

protected MessageToMessageEncoder(Class<? extends I> outboundMessageType)

Create a new instance

Parameters:

outboundMessageType - The type of messages to match and so encode

Method Detail

acceptOutboundMessage

public boolean acceptOutboundMessage(Object msg)
                              throws Exception

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

Throws:

Exception

write

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

Description copied from class: ChannelOutboundHandlerAdapter

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 ChannelOutboundHandlerAdapter

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

encode

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

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

Parameters:

ctx - the ChannelHandlerContext which this MessageToMessageEncoder belongs to

msg - the message to encode to an other one

out - the List into which the encoded msg should be added needs to do some kind of aggregation

Throws:

Exception - is thrown if an error occurs