Hi Norman,
Apologies for the late response. The encoders in my example above were in
the wrong order which prevented the handlers from being invoked.
To briefly summarise my use case :
Type2 -> Type1 -> Outbound
I ended up with something similar to the following code snippets:
ChannelInitializer<DatagramChannel> datagramChannelInitializer = new
ChannelInitializer<DatagramChannel>() {
@Override
public void initChannel(DatagramChannel ch) throws
Exception {
ch.pipeline().addLast(new
DatagramPacketDecoder(new Type1Decoder()))
.addLast(new Type2MessageToMessageDecoder())
.addLast(new DatagramPacketEncoder<>(new
Type1Encoder())
.addLast(new
AddressEnvelopeType2MessageToMessageEncoder()));
}
}
public class UdpClient{
private final SocketAddress socketAddress
private Bootstrap bootstrap;
private Channel channel;
public UdpClient(SocketAddress socketAddress)
{
this.socketAddress = socketAddress;
this.bootstrap = new Bootstrap();
this.bootstrap.handler(channelInitializer);
}
public void write(Type2 message, boolean await) {
AddressedEnvelope<Type2, SocketAddress> addressedEnvelope = new
DefaultAddressedEnvelope<Type2, SocketAddress>(message,
socketAddress, channel.localAddress());
if (await) {
channel.writeAndFlush(addressedEnvelope).awaitUninterruptibly();
} else {
channel.writeAndFlush(addressedEnvelope, channel.voidPromise());
}
}
}
public class AddressEnvelopeType2MessageToMessageEncoder
extends MessageToMessageEncoder<AddressedEnvelope<Type2,
SocketAddress>> {
@Override
protected void encode(ChannelHandlerContext ctx, AddressedEnvelope<
Type2Message, SocketAddress> envelope,
List<Object> out) throws Exception {
out.add(new DefaultAddressedEnvelope<Type1, SocketAddress>(
new Type1(envelope.content().getParameter()),
envelope.recipient(), envelope.sender()));
}
}
The UdpClient class is instantiated with the socketAddress of the remote
server. If I'd like to reuse the Netty AddressedEnvelope for addressing
purposes and also transform the message using a
MessageToMessageEncoder/Decoder in the channel pipeline, I have to create a
MessageToMessageEncoder similar to the one above.
Is there a better way of doing this?
Since it's possible to put multiple MessageToMessage encoder/decoders on
the same channel pipeline It would be nice to be able to preserve the
Address information along the pipeline for the UDP use case. I attempted
to create a generic MessageToMessageEncoder that would do this similar in
nature to the DatagramPacketEncoder which would delegate to a provided
encoder. I didn't have alot of time in the end so opted for the approach
above.
Cheers,
Joe
On Thursday, 4 August 2016 14:11:36 UTC+1, Joseph Madden wrote:
>
> Hi,
>
> I'd like to use a MessageToMessageDecoder to transform from one type to
> another while sending a message from a client to a remote server. The
> MessageToMessage Encoder/Decoder allow this to be accomplished easily.
> When using UDP and an AddressedEnvelope to preserve remote address info,
> this is not the case.
>
> The following snippet shows a simplified channel pipeline to hopefully
> illustrate my use case.
>
> ChannelInitializer<DatagramChannel> datagramChannelInitializer = new
> ChannelInitializer<DatagramChannel>() {
> @Override
> public void initChannel(DatagramChannel ch) throws
> Exception {
>
> ch.pipeline().addLast(new
> DatagramPacketDecoder(new Type1Decoder()))
> .addLast(new
> Type2MessageToMessageDecoder())
> .addLast(new
> Type2MessageToMessageEncoder())
> .addLast(new DatagramPacketEncoder<>(new
> Type1Encoder()));
> }
> }
>
>
> During encoding, I wrap my type1 payload in an AddressedEnvelope to
> specify the remote address. The Type2MessageToMessageEncoder is never
> invoked because AddressedEnvelope<Type1, SocketAddress> does not match
> Type2. I tried to create my own class
> AddressedEnvelopeMessageToMessageEncoder similar to the
> DatagramPacketEncoder which delegates to a provided encoder but the encode
> method is not visible.
>
> What is the recommended approach for this kind of use case? Any help
> appreciated.
>
> Thanks,
>
> Joe
>
>
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