标签:for current environ pac let work ace 调用 应该
本文承接上文:springboot源码分析(五)-监听器实现原理(中)
上一篇文章已经把springboot中的监听器从源码的角度分析了一遍,有兴趣的可以去看一下,如果不想看源码,只是看一下如何自定义监听器,也可以一下这篇文章,这篇文章主要介绍一下自定义监听器的方法,以及如何让自定义的监听器生效,初次之外呢,还会介绍一下springboot在启动过程中都有哪些事件,执行的顺序是什么。
@Order(1) public class FirstApplicationListener implements ApplicationListener<ApplicationStartedEvent> { @Override public void onApplicationEvent(ApplicationStartedEvent applicationStartedEvent) { System.out.println("first, springboot start"); } }
这是第一个监听器,我们实现了ApplicationListener接口,并且在接口中我们指定了ApplicationStartedEvent作为我们感兴趣的事件,当springboot启动是,调用到 listeners.starting(); 的时候,就会被我们自定义的监听器监听到,会执行我们重写的onApplicationEvent方法。
我们还是老规矩,在resource目录下新建META-INF目录,之后在这个目录下新建spring.factories文件,在文件中加入如下配置项
org.springframework.context.ApplicationListener=com.example.demo.listener.FirstApplicationListener
等号后面是我们自定义的监听器的路径,大家根据自己的路径填写。
ok我们启动springboot项目,可以看到如下打印结果:
. ____ _ __ _ _ /\\ / ___‘_ __ _ _(_)_ __ __ _ \ \ \ ( ( )\___ | ‘_ | ‘_| | ‘_ \/ _` | \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ‘ |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.2.6.RELEASE) firstApplicationContextInitializer is start thirdApplicationContextInitializer is start secondApplicationContextInitializer is start 2020-06-04 19:58:56.194 INFO 56577 --- [ main] com.example.demo.DemoApplication : Starting DemoApplication on ganxinledeMacBook-Pro.local with PID 56577 (/Users/ganxinle/workspace/demo/target/classes started by ganxinle in /Users/ganxinle/workspace/demo) 2020-06-04 19:58:56.197 INFO 56577 --- [ main] com.example.demo.DemoApplication : No active profile set, falling back to default profiles: default 2020-06-04 19:58:56.920 INFO 56577 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http) 2020-06-04 19:58:56.929 INFO 56577 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat] 2020-06-04 19:58:56.930 INFO 56577 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.33] 2020-06-04 19:58:56.987 INFO 56577 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2020-06-04 19:58:56.987 INFO 56577 --- [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 752 ms 2020-06-04 19:58:57.115 INFO 56577 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService ‘applicationTaskExecutor‘ 2020-06-04 19:58:57.243 INFO 56577 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ‘‘ 2020-06-04 19:58:57.246 INFO 56577 --- [ main] com.example.demo.DemoApplication : Started DemoApplication in 1.328 seconds (JVM running for 1.662) first, springboot start
说明我们的配置成功了,但是有的小伙伴可能有疑问,为什么是最后打印的,这个有兴趣的小伙伴自己去探究,我没有深究??
@Order(1) public class SecondApplicationListener implements SmartApplicationListener { @Override public boolean supportsEventType(Class<? extends ApplicationEvent> aClass) { if (ApplicationStartedEvent.class.isAssignableFrom(aClass)){ return true; } return false; } @Override public void onApplicationEvent(ApplicationEvent applicationEvent) { System.out.println("second,springboot start"); } }
我们实现了里面的两个方法,第一个方法就是在上一篇文章讲的,当寻找对当前事件感兴趣的监听器的时候,会调用这个方法来判断,我们在if中使用了isAssignableFrom方法来判断当前事件是不是ApplicationStartedEvent事件的字类或者是他本身,对这个方法不太熟悉的,我会在附录中把解释这个的文章的链接贴出来,大家看一下就明白了。
我们修改springboot的启动类,把这个监听器加入到监听器列表中
@SpringBootApplication public class DemoApplication { public static void main(String[] args) { SpringApplication application = new SpringApplication(DemoApplication.class); application.addListeners(new SecondApplicationListener()); application.run(args); } }
至于为什么这样可以生效,大家可以看一下上一篇文章,我这里就不重复了。
??,我们启动springboot项目
. ____ _ __ _ _ /\\ / ___‘_ __ _ _(_)_ __ __ _ \ \ \ ( ( )\___ | ‘_ | ‘_| | ‘_ \/ _` | \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ‘ |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.2.6.RELEASE) firstApplicationContextInitializer is start thirdApplicationContextInitializer is start secondApplicationContextInitializer is start 2020-06-04 19:58:56.194 INFO 56577 --- [ main] com.example.demo.DemoApplication : Starting DemoApplication on ganxinledeMacBook-Pro.local with PID 56577 (/Users/ganxinle/workspace/demo/target/classes started by ganxinle in /Users/ganxinle/workspace/demo) 2020-06-04 19:58:56.197 INFO 56577 --- [ main] com.example.demo.DemoApplication : No active profile set, falling back to default profiles: default 2020-06-04 19:58:56.920 INFO 56577 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http) 2020-06-04 19:58:56.929 INFO 56577 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat] 2020-06-04 19:58:56.930 INFO 56577 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.33] 2020-06-04 19:58:56.987 INFO 56577 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2020-06-04 19:58:56.987 INFO 56577 --- [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 752 ms 2020-06-04 19:58:57.115 INFO 56577 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService ‘applicationTaskExecutor‘ 2020-06-04 19:58:57.243 INFO 56577 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ‘‘ 2020-06-04 19:58:57.246 INFO 56577 --- [ main] com.example.demo.DemoApplication : Started DemoApplication in 1.328 seconds (JVM running for 1.662) first, springboot start second,springboot start
可以发现第二个也顺利打印出来了。
以上我只列举了两种把自定义监听器加入到系统的中方法,其实还有别的方法,我这里就不介绍了,知道这两种我觉得就够了。
从启动开始分别执行的事件如下:
ApplicationStartingEvent -> ApplicationEnvironmentPreparedEvent -> ApplicationContextInitializedEvent -> ApplicationPreparedEvent -> ApplicationStartedEvent -> ApplicationReadyEvent
启动失败执行ApplicationFailedEvent事件
这些个事件基本都是SpringApplicationEvent的子类。
基本上来说如果看过上一篇文章之后,对于这一篇介绍的自定义监听器应该很容易理解,至于后面的执行的事件的流程那个东东,需要对整个springboot的启动流程有一个很清楚的了解,这个现在可以先了解一下,以后会慢慢分享。
番外话:监听器系列写完了,终于知道springboot中是怎么使用设计模式的了,以后如果自己实现什么大型一点的系统,就可以仿照这个玩意也搞一个监听器模式,??
标签:for current environ pac let work ace 调用 应该
原文地址:https://www.cnblogs.com/gunduzi/p/13045884.html