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

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.

Field Summary

Modifier and Type	Field and Description
private final TypeParameterMatcher	matcher

Constructor Summary

Access	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> The type of messages to match and so encode outboundMessageType) Create a new instance

Method Summary

Modifier and Type	Method and Description
public boolean	acceptOutboundMessage(Object msg) Returns `true` if the given message should be handled.
protected abstract void	encode(ChannelHandlerContext the `ChannelHandlerContext` which this `MessageToMessageEncoder` belongs to ctx, I the message to encode to an other one msg, List<Object> the `List` into which the encoded msg should be added needs to do some kind of aggregation out) Encode from one message to an other.
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.ChannelOutboundHandlerAdapter.write. Implements io.netty.channel.ChannelOutboundHandler.write. Calls `ChannelHandlerContext#write(Object, ChannelPromise)` to forward to the next `ChannelOutboundHandler` in the `ChannelPipeline`.
private static void	writePromiseCombiner(ChannelHandlerContext ctx, CodecOutputList out, ChannelPromise promise)
private static void	writeVoidPromise(ChannelHandlerContext ctx, CodecOutputList out)

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

Field Detail

matcher	back to summary
private final TypeParameterMatcher matcher

Constructor Detail

MessageToMessageEncoder	back to summary
protected MessageToMessageEncoder() Create a new instance which will try to detect the types to match out of the type parameter of the class.

MessageToMessageEncoder	back to summary
protected MessageToMessageEncoder(Class<? extends I> outboundMessageType) Create a new instance Parameters outboundMessageType:Class<? extends I> The type of messages to match and so encode

MessageToMessageEncoder

back to summary

protected MessageToMessageEncoder(Class<? extends I> outboundMessageType)

Create a new instance

Parameters

outboundMessageType:Class<? extends I>: The type of messages to match and so encode

Method Detail

acceptOutboundMessage	back to summary
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`.

encode back to summary

encode	back to summary
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:ChannelHandlerContext the `ChannelHandlerContext` which this `MessageToMessageEncoder` belongs to msg:I the message to encode to an other one out:List<Object> the `List` into which the encoded msg should be added needs to do some kind of aggregation Exceptions Exception: is thrown if an error occurs

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:ChannelHandlerContext: the ChannelHandlerContext which this MessageToMessageEncoder belongs to
msg:I: the message to encode to an other one
out:List<Object>: the List into which the encoded msg should be added needs to do some kind of aggregation

Exceptions

Exception:: is thrown if an error occurs

write back to summary

write	back to summary
public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception Overrides io.netty.channel.ChannelOutboundHandlerAdapter.write. Implements io.netty.channel.ChannelOutboundHandler.write. Doc from io.netty.channel.ChannelOutboundHandlerAdapter.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