【ApplicationListener】Springboot各类事件监听器

Springboot中SpringApplicationEvent的种类

如下图：

主要包括6种：

1. ApplicationEnvironmentPreparedListener
2. ApplicationFailedListener
3. ApplicationPreparedListener
4. ApplicationReadyListener
5. ApplicationStartingListener
6. SpringApplicationListener

各监听器的启动顺序

如下是debug输出结果：

// 省略了部分
Connected to the target VM, address: '127.0.0.1:52000', transport: 'socket'
2017-09-28 16:53:27.273  INFO 6960 --- [           main] c.s.listeners.SpringApplicationListener  : 监听器事件 【SpringApplicationEvent】
2017-09-28 16:53:27.277  INFO 6960 --- [           main] l.ApplicationEnvironmentPreparedListener : 监听器事件 【ApplicationEnvironmentPreparedEvent】

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.5.7.RELEASE)

2017-09-28 16:53:27.359  INFO 6960 --- [           main] c.s.ApplicationlistenerApplication       : Starting ApplicationlistenerApplication on LIULIN-PC with PID 6960 (D:\workspace\SpringBootStudy\applicationlistener\target\classes started by liulin in D:\workspace\SpringBootStudy)
2017-09-28 16:53:27.359  INFO 6960 --- [           main] c.s.ApplicationlistenerApplication       : No active profile set, falling back to default profiles: default
2017-09-28 16:53:27.403  INFO 6960 --- [           main] c.s.l.ApplicationPreparedListener        : 监听器事件 【ApplicationPreparedEvent】
2017-09-28 16:53:27.403  INFO 6960 --- [           main] c.s.listeners.SpringApplicationListener  : 监听器事件 【SpringApplicationEvent】
2017-09-28 16:53:27.406  INFO 6960 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@2f465398: startup date [Thu Sep 28 16:53:27 CST 2017]; root of context hierarchy
2017-09-28 16:53:28.878  INFO 6960 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2017-09-28 16:53:28.887  INFO 6960 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2017-09-28 16:53:28.888  INFO 6960 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.5.20
2017-09-28 16:53:28.952  INFO 6960 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2017-09-28 16:53:28.952  INFO 6960 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1549 ms
2017-09-28 16:53:29.070  INFO 6960 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean  : Mapping servlet: 'dispatcherServlet' to [/]
2017-09-28 16:53:29.074  INFO 6960 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
2017-09-28 16:53:29.074  INFO 6960 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2017-09-28 16:53:29.074  INFO 6960 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2017-09-28 16:53:29.074  INFO 6960 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
2017-09-28 16:53:29.105  INFO 6960 --- [           main] com.ssslinppp.service.DemoServiceA       : 初始化实例：DemoServiceA
2017-09-28 16:53:29.107  INFO 6960 --- [           main] com.ssslinppp.service.DemoServiceB       : 初始化实例：DemoServiceB
2017-09-28 16:53:29.327  INFO 6960 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@2f465398: startup date [Thu Sep 28 16:53:27 CST 2017]; root of context hierarchy
2017-09-28 16:53:29.382  INFO 6960 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2017-09-28 16:53:29.382  INFO 6960 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
2017-09-28 16:53:29.420  INFO 6960 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-09-28 16:53:29.420  INFO 6960 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-09-28 16:53:29.451  INFO 6960 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-09-28 16:53:29.626  INFO 6960 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2017-09-28 16:53:29.668  INFO 6960 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
2017-09-28 16:53:29.671  INFO 6960 --- [           main] c.s.listeners.ApplicationReadyListener   : 监听器事件 【ApplicationReadyEvent】 ： ApplicationReadyListener
2017-09-28 16:53:29.671  INFO 6960 --- [           main] c.s.listeners.SpringApplicationListener  : 监听器事件 【SpringApplicationEvent】
2017-09-28 16:53:29.672  INFO 6960 --- [           main] c.s.ApplicationlistenerApplication       : Started ApplicationlistenerApplication in 2.577 seconds (JVM running for 3.022)

从上面可以看出，顺序如下：

1. SpringApplicationEvent
2. ApplicationEnvironmentPreparedEvent ：可以通过ConfigurableEnvironment实例对象来修改 以及 获取默认的环境信息。
3. 初始化图标（banner）
4. ApplicationPreparedEvent ：这个时候spring容器中的bean还没有被完全的加载，如果通过ConfigurableApplicationContext获取bean会报错的
5. SpringApplicationEvent
6. 映射基本的servlet URL： [/][/*]
7. 初始化Spring容器中的beans
8. ApplicationReadyEvent ：可以通过ApplicationReadyEvent获取ConfigurableApplicationContext，然后通过ConfigurableApplicationContext 获取bean的信息

各种SpringApplicationEvent的主要用途示例