延迟入站适配器和控制总线

Question

我的集成流程代码是：

@Bean
    public IntegrationFlow messageFlow() {
        return IntegrationFlows.from(stompInboundChannelAdapter())
                .transform(inBoundStompMsgTransformer::transform)
                .headerFilter("stomp_subscription","content-length")
                .handle(Amqp.outboundAdapter(outboundConfiguration.rabbitTemplate()))
                .get();
    }

我正在使用 Spring Boot。

日志清除表明{transformer}订阅者已添加到输入频道

2019-12-09 18:21:41.752  INFO 18248 --- [           main] o.s.i.s.i.StompInboundChannelAdapter     : started bean 'stompInboundChannelAdapter'; defined in: 'class path resource [com/mahesh/siuspdemo/adapter/InBoundStompAdapter.class]'; from source: 'org.springframework.core.type.classreading.SimpleMethodMetadata@21e360a'
2019-12-09 18:21:41.768  INFO 18248 --- [           main] o.s.i.endpoint.EventDrivenConsumer       : Adding {transformer} as a subscriber to the 'stompInputChannel' channel
2019-12-09 18:21:41.768  INFO 18248 --- [           main] o.s.integration.channel.DirectChannel    : Channel 'application.stompInputChannel' has 1 subscriber(s).
2019-12-09 18:21:41.768  INFO 18248 --- [           main] o.s.i.endpoint.EventDrivenConsumer       : started bean 'inboundFlow.org.springframework.integration.config.ConsumerEndpointFactoryBean#0'; defined in: 'class path resource [com/mahesh/siuspdemo/adapter/InBoundStompAdapter.class]'; from source: 'bean method inboundFlow'
2019-12-09 18:21:41.768  INFO 18248 --- [           main] o.s.i.endpoint.EventDrivenConsumer       : Adding {header-filter} as a subscriber to the 'inboundFlow.channel#0' channel
2019-12-09 18:21:41.772  INFO 18248 --- [           main] o.s.integration.channel.DirectChannel    : Channel 'application.inboundFlow.channel#0' has 1 subscriber(s).
2019-12-09 18:21:41.772  INFO 18248 --- [           main] o.s.i.endpoint.EventDrivenConsumer       : started bean 'inboundFlow.org.springframework.integration.config.ConsumerEndpointFactoryBean#1'; defined in: 'class path resource [com/mahesh/siuspdemo/adapter/InBoundStompAdapter.class]'; from source: 'bean method inboundFlow'
2019-12-09 18:21:41.772  INFO 18248 --- [           main] o.s.i.endpoint.EventDrivenConsumer       : Adding {amqp:outbound-channel-adapter} as a subscriber to the 'inboundFlow.channel#1' channel
2019-12-09 18:21:41.772  INFO 18248 --- [           main] o.s.integration.channel.DirectChannel    : Channel 'application.inboundFlow.channel#1' has 1 subscriber(s).
2019-12-09 18:21:41.772  INFO 18248 --- [           main] o.s.i.endpoint.EventDrivenConsumer       : started bean 'inboundFlow.org.springframework.integration.config.ConsumerEndpointFactoryBean#2'; defined in: 'class path resource [com/mahesh/siuspdemo/adapter/InBoundStompAdapter.class]'; from source: 'bean method inboundFlow'

但是，我遇到了一个异常，并且丢失了队列中的前一/两条消息。它处理剩余的消息。

假设在我启动应用程序之前队列中有 10 条消息。在我启动应用程序后，即使日志显示已添加订阅者并且已启动 bean，我也会收到异常，发布异常，处理 8/9 消息。

例外是：org.springframework.messaging.MessageDeliveryException: Dispatcher has no subscribers for channel 'application.stompInputChannel'.; nested exception is org.springframework.integration.MessageDispatchingException: Dispatcher has no subscribers, failedMessage=GenericMessage

很明显，上下文还没有完全准备好处理消息，因此出现了异常。 但日志消息具有误导性。

我的第一个问题：

1. 那么添加订阅者并启动 bean 究竟意味着什么？这是否意味着一切都已设置好，但上下文仍必须准备好处理消息？

为了克服这个问题，正如许多帖子中所建议的那样，我使用控制总线来启动适配器。代码是：

......
@Component
public class ApplicationLifeCycle implements SmartLifecycle {

    @Autowired
    private MessageChannel controlBusChannel;

    @Override
    public void start() {
        System.out.println("Service starting...");
        controlBusChannel.send(new GenericMessage<>("@stompInboundChannelAdapter.start()"));
    }
.....

我创建了public class ApplicationLifeCycle implements SmartLifecycle 认为它会很方便。

我的第二个问题是：

1. 这是使用控制总线处理适配器启动/停止的正确/最佳方式吗？如果不是正确的方法，请告诉我正确的方法。

谢谢，

马赫什

Answer 1

我认为这是您其他问题的延续：IntegrationFlow Amqp Channel Adapter is not working in handle()

你有这个：

@Bean
public StompInboundChannelAdapter stompInboundChannelAdapter() {
    StompInboundChannelAdapter adapter = new StompInboundChannelAdapter(stompSessionManager(), "/queue/myQueue");
    adapter.setOutputChannel(stompInputChannel());
    adapter.setPayloadType(ByteString.class);
    return adapter;
}

你没有在这里显示。

问题是你在IntegrationFlow 中使用了相同的定义。原来StompInboundChannelAdapter bean 更早启动，然后IntegationFlow 被处理，.transform(inBoundStompMsgTransformer::transform) 被订阅处理传入消息。

因此，如果您将 @Bean 从 stompInboundChannelAdapter() 中删除，它应该可以正常工作。后面我看看为什么MessageProducerSupport启动得更早，然后IntegrationFlows...