The `MessagingAnnotationPostProcessor` registers a `Disposables` unconditionally. The `afterPropertiesSet()` maybe called several times, so `IntegrationContextUtils.DISPOSABLES_BEAN_NAME` registration has to be idempotent. * Add `if (!this.beanFactory.containsBeanDefinition(IntegrationContextUtils.DISPOSABLES_BEAN_NAME))` before trying to register `Disposables` bean