如何在netty中存储具有用户名和ChannelHandlerContext的用户列表

Question

i try to send an message ot an specific user in netty. For this i need to store the username and the CahnnelHandlerContext in an Arralist, that i can check if the user is connectet to the server and get the ChannelhandlerContext for the specific user.

Can you tell me the best practice for this?

Here some code of the Server where i handle the connections:

import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.ssl.SslHandler;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.GenericFutureListener;
import java.util.ArrayList;
import messages.SecureMessageServerClientMessage;
import messages.SecureMessageServerUser;

/**
 * Handles a server-side channel.
 */
public class SecureChatServerHandler extends SimpleChannelInboundHandler<SecureMessageServerClientMessage> {

    protected ArrayList<SecureMessageServerUser> userList = new ArrayList();

    @Override
    public void channelActive(final ChannelHandlerContext ctx) {
        // Once session is secured, send a greeting and register the channel to the global channel
        // list so the channel received the messages from others.
        ctx.pipeline().get(SslHandler.class).handshakeFuture().addListener(
                new GenericFutureListener<Future<Channel>>() {
                    @Override
                    public void operationComplete(Future<Channel> future) throws Exception {
                    userList.add(new SecureMessageServerUser("", ctx));
                    }
        });
    }

    @Override
    public void channelRead0(ChannelHandlerContext ctx, SecureMessageServerClientMessage msg ) throws Exception {
        switch(msg.getType()){
                case 0:
                    ctx.writeAndFlush(new SecureMessageServerClientMessage(0, this.userList));
                    break;
                case 1:
                    System.out.println("TestMessage Typ 1");
                    String empfaenger, sender, message;
                    sender=msg.getSender();
                    empfaenger = msg.getEmpfaenger();
                    message = msg.getMessage();
                    for (SecureMessageServerUser user : this.userList) {
                    System.out.println(user.getUserName());
//                    if (user.getUserName().equals(empfaenger)) {
//                     user.getCtx().writeAndFlush(new SecureMessageServerClientMessage(1, message, sender));
//                    }
                    }
                    Thread.sleep(1000);
                    break;
                case 2://User aus Liste löschen und alle Resorucen freigeben

                case 3: //Liste mit allen Benutzern an Clienten senden
                    ctx.writeAndFlush(new SecureMessageServerClientMessage(0, this.userList));
                    break;
                default:
                    System.out.println("Unbekannter Nachrichtentyp");
            }        
    }

    @Override
    public void channelUnregistered(final ChannelHandlerContext ctx) {

    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

Answer 1

I think storing it in a ConcurrentMap would be the best using the username as key and the ChannelHandlerContext as value. Also note this has not really anything todo with Netty put more with what data structure to use for store a mapping from key to to value.