Netty/Codec 4.1.107.Final · io.netty.handler.codec.MessageToMessageCodec

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.

Modifier and Type	Field and Description
private final MessageToMessageDecoder<Object>	decoder
private final MessageToMessageEncoder<Object>	encoder
private final TypeParameterMatcher	inboundMsgMatcher
private final TypeParameterMatcher	outboundMsgMatcher

Constructor Summary

Access	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> The type of messages to decode inboundMessageType, Class<? extends OUTBOUND_IN> The type of messages to encode outboundMessageType) Create a new instance.

Method Summary

Modifier and Type	Method and Description
public boolean	acceptInboundMessage(Object the message msg) Returns `true` if and only if the specified message can be decoded by this codec.
public boolean	acceptOutboundMessage(Object the message msg) Returns `true` if and only if the specified message can be encoded by this codec.
public void	channelRead(ChannelHandlerContext ctx, Object msg) Overrides io.netty.channel.ChannelInboundHandlerAdapter.channelRead. Implements io.netty.channel.ChannelInboundHandler.channelRead. 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)
public void	write(ChannelHandlerContext the `ChannelHandlerContext` for which the write operation is made ctx, Object the message to write msg, ChannelPromise the `ChannelPromise` to notify once the operation completes promise) Overrides io.netty.channel.ChannelDuplexHandler.write. Implements io.netty.channel.ChannelOutboundHandler.write. Calls `ChannelHandlerContext#write(Object, ChannelPromise)` to forward to the next `ChannelOutboundHandler` in the `ChannelPipeline`.

Inherited from io.netty.channel.ChannelDuplexHandler:: bind close connect deregister disconnect flush read

Field Detail

decoder	back to summary
private final MessageToMessageDecoder<Object> decoder

encoder	back to summary
private final MessageToMessageEncoder<Object> encoder

inboundMsgMatcher	back to summary
private final TypeParameterMatcher inboundMsgMatcher

outboundMsgMatcher	back to summary
private final TypeParameterMatcher outboundMsgMatcher

Constructor Detail

MessageToMessageCodec	back to summary
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	back to summary
protected MessageToMessageCodec(Class<? extends INBOUND_IN> inboundMessageType, Class<? extends OUTBOUND_IN> outboundMessageType) Create a new instance. Parameters inboundMessageType:Class<? extends INBOUND_IN> The type of messages to decode outboundMessageType:Class<? extends OUTBOUND_IN> The type of messages to encode

MessageToMessageCodec

back to summary

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

Create a new instance.

Parameters

inboundMessageType:Class<? extends INBOUND_IN>: The type of messages to decode
outboundMessageType:Class<? extends OUTBOUND_IN>: The type of messages to encode

Method Detail

acceptInboundMessage back to summary

acceptInboundMessage	back to summary
public boolean acceptInboundMessage(Object msg) throws Exception Returns `true` if and only if the specified message can be decoded by this codec. Parameters msg:Object the message

public boolean acceptInboundMessage(Object msg) throws Exception

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

Parameters

msg:Object: the message

acceptOutboundMessage back to summary

acceptOutboundMessage	back to summary
public boolean acceptOutboundMessage(Object msg) throws Exception Returns `true` if and only if the specified message can be encoded by this codec. Parameters msg:Object the message

public boolean acceptOutboundMessage(Object msg) throws Exception

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

Parameters

msg:Object: the message

channelRead back to summary

channelRead	back to summary
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception Overrides io.netty.channel.ChannelInboundHandlerAdapter.channelRead. Implements io.netty.channel.ChannelInboundHandler.channelRead. Doc from io.netty.channel.ChannelInboundHandlerAdapter.channelRead. Calls `ChannelHandlerContext#fireChannelRead(Object)` to forward to the next `ChannelInboundHandler` in the `ChannelPipeline`. Sub-classes may override this method to change behavior. Annotations @Override

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

Overrides io.netty.channel.ChannelInboundHandlerAdapter.channelRead.

Implements io.netty.channel.ChannelInboundHandler.channelRead.

Doc from io.netty.channel.ChannelInboundHandlerAdapter.channelRead.

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

Annotations

@Override

decode	back to summary
protected abstract void decode(ChannelHandlerContext ctx, INBOUND_IN msg, List<Object> out) throws Exception See Also `MessageToMessageDecoder#decode(ChannelHandlerContext, Object, List)`

encode	back to summary
protected abstract void encode(ChannelHandlerContext ctx, OUTBOUND_IN msg, List<Object> out) throws Exception See Also `MessageToMessageEncoder#encode(ChannelHandlerContext, Object, List)`

write back to summary

write	back to summary
public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception Overrides io.netty.channel.ChannelDuplexHandler.write. Implements io.netty.channel.ChannelOutboundHandler.write. Doc from io.netty.channel.ChannelDuplexHandler.write. Calls `ChannelHandlerContext#write(Object, ChannelPromise)` to forward to the next `ChannelOutboundHandler` in the `ChannelPipeline`. Sub-classes may override this method to change behavior. Parameters ctx:ChannelHandlerContext Doc from io.netty.channel.ChannelOutboundHandler.write. the `ChannelHandlerContext` for which the write operation is made msg:Object Doc from io.netty.channel.ChannelOutboundHandler.write. the message to write promise:ChannelPromise Doc from io.netty.channel.ChannelOutboundHandler.write. the `ChannelPromise` to notify once the operation completes Annotations @Override Exceptions Exception: Doc from io.netty.channel.ChannelOutboundHandler.write. thrown if an error occurs