management.endpoint.gateway.enabled = true          # 这个值默认就是true，所以不是必须的
management.endpoints.web.exposure.include = gateway # 暴露/gateway/*端点

    ...
    @PostMapping("/refresh")
    public Mono<Void> refresh() {
        // publishEvent()方法，具体调用的是ReactiveWebServerApplicationContext的父类
        // org.springframework.context.support.AbstractApplicationContext里的publishEvent()
        // publishEvent()方法的入参RefreshRoutesEvent继承了ApplicationEvent
        this.publisher.publishEvent(new RefreshRoutesEvent(this));

        return Mono.empty();
    }
    ...

    ...
    /**
     * Publish the given event to all listeners.
     * @param event the event to publish (may be an {@link ApplicationEvent}
     * or a payload object to be turned into a {@link PayloadApplicationEvent})
     * @param eventType the resolved event type, if known
     * @since 4.2
     */
    protected void publishEvent(Object event, @Nullable ResolvableType eventType) {
        Assert.notNull(event, "Event must not be null");

        // Decorate event as an ApplicationEvent if necessary
        // 1 把入参的object转化为ApplicationEvent
        ApplicationEvent applicationEvent;
        if (event instanceof ApplicationEvent) {
            applicationEvent = (ApplicationEvent) event;
        }
        else {
            applicationEvent = new PayloadApplicationEvent<>(this, event);
            if (eventType == null) {
                eventType = ((PayloadApplicationEvent<?>) applicationEvent).getResolvableType();
            }
        }

        // Multicast right now if possible - or lazily once the multicaster is initialized
        if (this.earlyApplicationEvents != null) {
            this.earlyApplicationEvents.add(applicationEvent);
        }
        else {
            // 2 监听器处理 RefreshRoutesEvent
            // 2.1 DelegatingApplicationListener#onApplicationEvent，什么都没做
            // 2.2 WeightCalculatorWebFilter#onApplicationEvent，强制初始化？？
            // 2.3 RouteRefreshListener#onApplicationEvent，什么都没做
            // 2.4 CachingRouteLocator#onApplicationEvent，清理了CachingRouteLocator里的cache map；会对路由产生什么影响？？
            getApplicationEventMulticaster().multicastEvent(applicationEvent, eventType);
        }

        // Publish event via parent context as well...
        if (this.parent != null) {
            // parent 是 AnnotationConfigApplicationContext 继承了 AbstractApplicationContext
            if (this.parent instanceof AbstractApplicationContext) {
                ((AbstractApplicationContext) this.parent).publishEvent(event, eventType);
            }
            else {
                this.parent.publishEvent(event);
            }
        }
    }

    private final ObjectProvider<RouteLocator> routeLocator;
    ...
    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof PredicateArgsEvent) {
            handle((PredicateArgsEvent) event);
        }
        else if (event instanceof WeightDefinedEvent) {
            addWeightConfig(((WeightDefinedEvent) event).getWeightConfig());
        }
        else if (event instanceof RefreshRoutesEvent && routeLocator != null) {
            // 调用了CachingRouteLocator#getRoutes，然后Flux#subscribe，？？
            routeLocator.ifAvailable(locator -> locator.getRoutes().subscribe()); // forces initialization
        }
    }