CamelContextStartedEvent 调用了两次

Question

对于同一个 camel 上下文 (camel-1)，CamelContextStartedEvent 被调用了两次。问题可能是我注册 EventNotifier 的方式。您可以使用 Spring Initializr 和 Spring Boot 1.5.14、Spring Boot Camel Starter 2.21.1 和 Spring Boot Web Starter 重现该问题。

查看日志：

2018-07-06 11:04:41.104  INFO 19092 --- [           main] o.a.camel.spring.SpringCamelContext      : Apache Camel 2.21.1 (CamelContext: camel-1) is starting
2018-07-06 11:04:41.106  INFO 19092 --- [           main] o.a.c.m.ManagedManagementStrategy        : JMX is enabled
2018-07-06 11:04:41.191  INFO 19092 --- [           main] o.a.camel.spring.SpringCamelContext      : StreamCaching is not in use. If using streams then its recommended to enable stream caching. See more details at http://camel.apache.org/stream-caching.html
2018-07-06 11:04:41.193  INFO 19092 --- [           main] o.a.camel.spring.boot.RoutesCollector    : Starting CamelMainRunController to ensure the main thread keeps running
2018-07-06 11:04:41.193  INFO 19092 --- [           main] o.a.camel.spring.SpringCamelContext      : Total 0 routes, of which 0 are started
2018-07-06 11:04:41.194  INFO 19092 --- [           main] o.a.camel.spring.SpringCamelContext      : Apache Camel 2.21.1 (CamelContext: camel-1) started in 0.090 seconds
2018-07-06 11:04:41.195  INFO 19092 --- [           main] c.e.bug.service.StartupEventNotifier     : CamelContextStartedEvent for SpringCamelContext(camel-1) with spring id application:11223
2018-07-06 11:04:41.195  INFO 19092 --- [           main] c.e.bug.service.StartupEventNotifier     : CamelContextStartedEvent for SpringCamelContext(camel-1) with spring id application:11223
2018-07-06 11:04:41.216  INFO 19092 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 11223 (http)
2018-07-06 11:04:41.221  INFO 19092 --- [           main] com.example.bug.BugApplication           : Started BugApplication in 4.684 seconds (JVM running for 6.773)

初始化EventNotifier的服务：

@Service
public class SchedulerService {

    private final CamelContext camelContext;

    private final StartupEventNotifier startupEventNotifier;

    public SchedulerService(CamelContext camelContext, StartupEventNotifier startupEventNotifier) {
        this.camelContext = camelContext;
        this.startupEventNotifier = startupEventNotifier;
    }

    @PostConstruct
    public void init() {
        camelContext.getManagementStrategy().addEventNotifier(startupEventNotifier);
    }

}

EventNotifier：

@Component
public class StartupEventNotifier extends EventNotifierSupport {

    private static final Logger logger = LoggerFactory.getLogger(StartupEventNotifier.class);

    @Override
    public void notify(EventObject event) throws Exception {
        if (event instanceof CamelContextStartedEvent) {
            logger.info("CamelContextStartedEvent for {}", event.getSource());
        }
    }

    @Override
    public boolean isEnabled(EventObject event) {
        if (event instanceof CamelContextStartedEvent) {
            return true;
        }
        return false;
    }
}

application.yml:

camel:
  springboot:
    main-run-controller: true
server:
  port: 11223

Answer 1

调用了两次，因为注册了两次。一次是你，一次是 Apache Camel。如果在 Registry 中找到 EventNotifier，则会自动注册。由于您的 StartupEventNotifier 被注释为 Component，它是 Registry 的一部分并且 Apache Camel 在 CamelContext 启动期间注册了它 （您可以在 CamelAutoConfiguration 第 424 行).

你有四种选择：

从 SchedulerService 中删除您的自定义注册。
从 StartupEventNotifier 中删除 @Component 注释并使用 camelContext.getManagementStrategy().addEventNotifier(new StartupEventNotifier())

为您的 SchedulerService 添加口是心非检查。类似于：

if (!context.getManagementStrategy().getEventNotifiers().contains(startupEventNotifier)){
    context.getManagementStrategy().addEventNotifier(startupEventNotifier);
}

在 RouteBuilder 的 @PostConstruct 中注册 EventNotifier。它会在自动发现开始之前注册，然后在CamelAutoConfiguration （见第422行）

CamelContextStartedEvent 调用了两次

CamelContextStartedEvent called twice

spring

spring-boot

apache-camel

spring-camel