onSubscribe() — netty Function Reference

Architecture documentation for the onSubscribe() function in StompChatHandler.java from the netty codebase.

Function java Buffer Telemetry calls 1 called by 1

Entity Profile

Buffer→ Telemetry→ onSubscribe() — netty Function Reference

Dependency Diagram

graph TD
  91529c34_98b8_0877_0e3c_4566c29cc41c["onSubscribe()"]
  f937e446_8aba_2036_93fc_8020adb1953f["StompChatHandler"]
  91529c34_98b8_0877_0e3c_4566c29cc41c -->|defined in| f937e446_8aba_2036_93fc_8020adb1953f
  5ef12430_b789_c7f8_301d_8283d302e997["channelRead0()"]
  5ef12430_b789_c7f8_301d_8283d302e997 -->|calls| 91529c34_98b8_0877_0e3c_4566c29cc41c
  f5104c6e_035e_0b9d_444a_4cc359d713bf["sendErrorFrame()"]
  91529c34_98b8_0877_0e3c_4566c29cc41c -->|calls| f5104c6e_035e_0b9d_444a_4cc359d713bf
  style 91529c34_98b8_0877_0e3c_4566c29cc41c fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

example/src/main/java/io/netty/example/stomp/websocket/StompChatHandler.java lines 76–111

    private void onSubscribe(ChannelHandlerContext ctx, StompFrame inboundFrame) {
        String destination = inboundFrame.headers().getAsString(DESTINATION);
        String subscriptionId = inboundFrame.headers().getAsString(ID);

        if (destination == null || subscriptionId == null) {
            sendErrorFrame("missed header", "Required 'destination' or 'id' header missed", ctx);
            return;
        }

        Set<StompSubscription> subscriptions = chatDestinations.get(destination);
        if (subscriptions == null) {
            subscriptions = new HashSet<StompSubscription>();
            Set<StompSubscription> previousSubscriptions = chatDestinations.putIfAbsent(destination, subscriptions);
            if (previousSubscriptions != null) {
                subscriptions = previousSubscriptions;
            }
        }

        final StompSubscription subscription = new StompSubscription(subscriptionId, destination, ctx.channel());
        if (subscriptions.contains(subscription)) {
            sendErrorFrame("duplicate subscription",
                           "Received duplicate subscription id=" + subscriptionId, ctx);
            return;
        }

        subscriptions.add(subscription);
        ctx.channel().closeFuture().addListener(f ->
                chatDestinations.get(subscription.destination()).remove(subscription));

        String receiptId = inboundFrame.headers().getAsString(RECEIPT);
        if (receiptId != null) {
            StompFrame receiptFrame = new DefaultStompFrame(StompCommand.RECEIPT);
            receiptFrame.headers().set(RECEIPT_ID, receiptId);
            ctx.writeAndFlush(receiptFrame);
        }
    }