ApplicationStartedEvent
事件,所以在2.0版本中所有的事件按执行的先后顺序如下:
ApplicationStartingEvent
ApplicationEnvironmentPreparedEvent
ApplicationPreparedEvent
ApplicationStartedEvent
<= 新增的事件ApplicationReadyEvent
ApplicationFailedEvent
从上面的列表中,我们可以看到ApplicationStartedEvent
位于ApplicationPreparedEvent
之后,ApplicationReadyEvent
之前。
下面我们通过代码的方式来直观的感受这个事件的切入位置,以便与将来我们在这个切入点加入自己需要的逻辑。
第一步:我们可以编写ApplicationPreparedEvent
、ApplicationStartedEvent
以及ApplicationReadyEvent
三个事件的监听器,然后在这三个事件触发的时候打印一些日志来观察它们各自的切入点,比如:
@Slf4j public class ApplicationPreparedEventListener implements ApplicationListener<ApplicationPreparedEvent> { @Override public void onApplicationEvent(ApplicationPreparedEvent event) { log.info("......ApplicationPreparedEvent......"); } } @Slf4j public class ApplicationStartedEventListener implements ApplicationListener<ApplicationStartedEvent> { @Override public void onApplicationEvent(ApplicationStartedEvent event) { log.info("......ApplicationStartedEvent......"); } } @Slf4j public class ApplicationReadyEventListener implements ApplicationListener<ApplicationReadyEvent> { @Override public void onApplicationEvent(ApplicationReadyEvent event) { log.info("......ApplicationReadyEvent......"); } } |
第二步:在/src/main/resources/
目录下新建:META-INF/spring.factories
配置文件,通过配置org.springframework.context.ApplicationListener
来加载上面我们编写的监听器。
org.springframework.context.ApplicationListener= com.didispace.ApplicationPreparedEventListener,\ com.didispace.ApplicationReadyEventListener,\ com.didispace.ApplicationStartedEventListener |
此时,我们运行Spring Boot应用可以获得类似如下日志输出:
下面可以看看官方文档对ApplicationStartedEvent
和ApplicationReadyEvent
的解释:从日志中我们可以看到清晰的看到ApplicationPreparedEvent
、ApplicationStartedEvent
以及ApplicationReadyEvent
三个事件的切入点。通过这个例子可能读者会感到疑问:ApplicationStartedEvent
和ApplicationReadyEvent
从事件命名和日志输出位置来看,都是应用加载完成之后的事件,它们是否有什么区别呢?
An ApplicationStartedEvent is sent after the context has been refreshed but before any application and command-line runners have been called.An ApplicationReadyEvent is sent after any application and command-line runners have been called. It indicates that the application is ready to service requests
从文档中我们可以知道他们两中间还有一个过程就是command-line runners
被调用的内容。所以,为了更准确的感受这两个事件的区别,我们在应用主类中加入CommandLineRunner
的实现,比如:
@Slf4j @SpringBootApplication public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } @Bean public DataLoader dataLoader() { return new DataLoader(); } @Slf4j static class DataLoader implements CommandLineRunner { @Override public void run(String... strings) throws Exception { log.info("Loading data..."); } } } |
最后,我们再运行程序,此时我们可以发现这两个事件中间输出了上面定义的DataLoader
的输出内容,具体如下:
2018-03-07 18:15:20.845 INFO 83387 --- [main] c.d.ApplicationStartedEventListener : ......ApplicationStartedEvent...... 2018-03-07 18:15:20.846 INFO 83387 --- [main] com.didispace.Application$DataLoader : Loading data... 2018-03-07 18:15:20.847 INFO 83387 --- [main] c.d.ApplicationReadyEventListener : ......ApplicationReadyEvent......zhua |
转载:http://blog.didispace.com/Spring-Boot-2-0-feature-2-ApplicationStartedEvent/