CODEWITHSUNDEEP
javamultithreadingsynchronizationthread-safetynetty
Alejandro Rioja
Alejandro Rioja

Reputation: 1

Netty, how to store data through all handlers

Im new to Netty and I have a question about storing the data received by clients in the server, for a later consult by whatever clients.

If I define the pipeline as follow:

ch.pipeline().addLast(new ServerHandler());

Can i define in my ServerHandler a class variable as follow ?

public class ServerHandler extends ChannelInboundHandlerAdapter {

private static final ArrayList<String> llamadas = new ArrayList<String>();
....

And after use it whitin all clients like this ?

synchronized(llamadas) {
            llamadas.add(mensaje);
}

Also I want to ask if there is any difference if I create only one instance of ServerHandler 

ch.pipeline().addLast(serverHandler);

and I annotate the class with @Sharable

make any difference in the access of the variable?

Many thanks!!

regards.

Upvotes: 0

Views: 712

Answers (1)

spinlok
spinlok

Reputation: 3661

This is more of a Java question than Netty-specific. Since llamadas is a static class member, you will need to synchronize regardless of whether you make your ChannelHandler @Sharable or not i.e whether you have multiple instances of the channel handler or only one, you have a single ArrayList you are appending to.

Generally, @Sharable is used with handlers that are "stateless" w.r.t channels i.e that do not maintain any channel-specific state, and so you can get away with using a single instance of the handler across pipelines. See this tutorial for a good explanation of this.

Upvotes: 1

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