Springboot扩展了Spring的ApplicatoionContextEvent，提供了事件：
ApplicationStartingEvent:框架启动事件
ApplicationEnvironmentPreparedEvent: springboot 对应Evironment已经准备完毕了，但是上下文还没有创建。
ApplicationContextInitializedEvent: 上下文初始化
ApplicationPreparedEvent: springboot 上下文context创建完成，但是bean没有完全加载
ApplicationStartedEvent: springboot 启动开始执行的事件
ApplicationReadyEvent : 调用Runners接口完毕
ApplicationFailedEvent：启动异常执行事件
* springboot自带的事件。 * ApplicationStartingEvent * Spring Application启动事件。事件产生的时机为ApplicationListeners注册之后，Environment或ApplicationContext可用之前，
事件源为Spring Application自身，ApplicationStartingEvent在生命周期过程中可能会被修改，请谨慎使用。
* ApplicationEnvironmentPreparedEvent * 事件产生的时机为Spring Application已经启动，Environment第一次可用。
* ApplicationPreparedEvent * 事件产生的时机为Spring Application已经启动，Application Context已经完全准备好但是还没有进行刷新，在该阶段已经开始加载Bean定义并且Environment已经完全可用。
* ApplicationStartedEvent * 事件产生的时机为Application Context已经完成刷新，ApplicationRunner application和CommandLineRunner调用之前。
* ApplicationReadyEvent * Spring Application已经准备好对外提供服务。
* ApplicationFailedEvent * 应用启动失败
自定义监听器的步骤：
1，建立监听类继承ApplicationListener
2, 继承方法onApplicationEvent
3, 在resource建立文件夹/META-INF/spring.factories
4, 文件里写入：
org.springframework.context.ApplicationListener=com.quan.sbrabbit.Listener.QuanListenerEnvPreparedEvent ,com.quan.sbrabbit.Listener.QuanListenerStartedEvent,com.quan.sbrabbit.Listener.QuanListenerPreparedEvent
/** * spring boot 对应Enviroment已经准备完毕，但此时上下文context还没有创建。在该监听中获取到ConfigurableEnvironment * 后可以对配置信息做操作，例如：修改默认的配置信息 */ public class QuanListenerEnvPreparedEvent implements ApplicationListener<ApplicationEnvironmentPreparedEvent> { @Override public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) { ConfigurableEnvironment environment = event.getEnvironment(); MutablePropertySources sources =environment.getPropertySources(); if (sources != null){ Iterator<PropertySource<?>> iterator = sources.iterator(); while (iterator.hasNext()){ PropertySource<?> propertySource = iterator.next(); System.out.println(propertySource.getName()); System.out.println(propertySource.getSource()); System.out.println(propertySource.getClass()); } System.out.println("监听到ApplicationEnvironmentPreparedEvent"); // for (PropertySource<?> p : // sources) { // System.out.println(p.getName()); // System.out.println(p.getSource()); // System.out.println(p.getClass()); // } } } }
/** * pring boot上下文context创建完成，但此时spring中的bean是没有完全加载完成的。 * 在获取完上下文后，可以将上下文传递出去做一些额外的操作。 * 值得注意的是：在该监听器中是无法获取自定义bean并进行操作的。 */ public class QuanListenerPreparedEvent implements ApplicationListener<ApplicationPreparedEvent> { @Override public void onApplicationEvent(ApplicationPreparedEvent event) { ConfigurableApplicationContext context = event.getApplicationContext(); context.toString(); System.out.println("监听到ApplicationPreparedEvent"); } }
public class QuanListenerStartedEvent implements ApplicationListener<ApplicationStartedEvent> { @Override public void onApplicationEvent(ApplicationStartedEvent event) { SpringApplication application = event.getSpringApplication(); System.out.println(application); //控制台或日志中会默认显示一个Banner,关闭这个东西 application.setBannerMode(Banner.Mode.OFF); System.out.println("监听到applicationStartedEvent"); } }
加入：
org.springframework.context.ApplicationListener=com.quan.sbrabbit.Listener.QuanListenerEnvPreparedEvent ,com.quan.sbrabbit.Listener.QuanListenerStartedEvent,com.quan.sbrabbit.Listener.QuanListenerPreparedEvent
运行输出：
监听到ApplicationEnvironmentPreparedEvent . ____ _ __ _ _ /\\ / ___‘_ __ _ _(_)_ __ __ _ \ \ \ ( ( )\___ | ‘_ | ‘_| | ‘_ \/ _` | \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ‘ |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.3.3.RELEASE) 2020-09-01 14:10:32.063 WARN 99192 --- [ main] o.s.boot.StartupInfoLogger : InetAddress.getLocalHost().getHostName() took 5004 milliseconds to respond. Please verify your network configuration (macOS machines may need to add entries to /etc/hosts). 2020-09-01 14:10:37.067 INFO 99192 --- [ main] com.quan.sbrabbit.SbrabbitApplication : Starting SbrabbitApplication on quandeMacBook-Pro.local with PID 99192 (/Users/quan/Desktop/ALLLL/sbrabbit/target/classes started by quan in /Users/quan/Desktop/ALLLL/sbrabbit) 2020-09-01 14:10:37.068 INFO 99192 --- [ main] com.quan.sbrabbit.SbrabbitApplication : No active profile set, falling back to default profiles: default 监听到ApplicationPreparedEvent 2020-09-01 14:10:37.491 INFO 99192 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data Elasticsearch repositories in DEFAULT mode. 2020-09-01 14:10:37.505 INFO 99192 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 11ms. Found 0 Elasticsearch repository interfaces. 2020-09-01 14:10:37.509 INFO 99192 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data Reactive Elasticsearch repositories in DEFAULT mode. 2020-09-01 14:10:37.511 INFO 99192 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 2ms. Found 0 Reactive Elasticsearch repository interfaces. 2020-09-01 14:10:37.762 INFO 99192 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 9898 (http) 2020-09-01 14:10:37.768 INFO 99192 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat] 2020-09-01 14:10:37.769 INFO 99192 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.37] 2020-09-01 14:10:37.838 INFO 99192 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2020-09-01 14:10:37.839 INFO 99192 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 740 ms 2020-09-01 14:10:38.006 INFO 99192 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService ‘applicationTaskExecutor‘ 2020-09-01 14:10:38.502 WARN 99192 --- [ main] o.s.data.convert.CustomConversions : Registering converter from class org.springframework.data.geo.Point to interface java.util.Map as writing converter although it doesn‘t convert to a store-supported type! You might want to check your annotation setup at the converter implementation. 2020-09-01 14:10:38.502 WARN 99192 --- [ main] o.s.data.convert.CustomConversions : Registering converter from interface java.util.Map to class org.springframework.data.geo.Point as reading converter although it doesn‘t convert from a store-supported type! You might want to check your annotation setup at the converter implementation. 2020-09-01 14:10:38.503 WARN 99192 --- [ main] o.s.data.convert.CustomConversions : Registering converter from class org.springframework.data.elasticsearch.core.geo.GeoPoint to interface java.util.Map as writing converter although it doesn‘t convert to a store-supported type! You might want to check your annotation setup at the converter implementation. 2020-09-01 14:10:38.503 WARN 99192 --- [ main] o.s.data.convert.CustomConversions : Registering converter from interface java.util.Map to class org.springframework.data.elasticsearch.core.geo.GeoPoint as reading converter although it doesn‘t convert from a store-supported type! You might want to check your annotation setup at the converter implementation. 2020-09-01 14:10:38.604 INFO 99192 --- [ main] o.s.d.elasticsearch.support.VersionInfo : Version Spring Data Elasticsearch: 4.0.3.RELEASE 2020-09-01 14:10:38.604 INFO 99192 --- [ main] o.s.d.elasticsearch.support.VersionInfo : Version Elasticsearch Client in build: 7.6.2 2020-09-01 14:10:38.605 INFO 99192 --- [ main] o.s.d.elasticsearch.support.VersionInfo : Version Elasticsearch Client used: 7.6.2 2020-09-01 14:10:38.605 INFO 99192 --- [ main] o.s.d.elasticsearch.support.VersionInfo : Version Elasticsearch cluster: 6.8.4 2020-09-01 14:10:38.605 WARN 99192 --- [ main] o.s.d.elasticsearch.support.VersionInfo : Version mismatch in between Elasticsearch Client and Cluster: 7.6.2 - 6.8.4 2020-09-01 14:10:38.688 INFO 99192 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 9898 (http) with context path ‘‘ 2020-09-01 14:10:38.698 INFO 99192 --- [ main] com.quan.sbrabbit.SbrabbitApplication : Started SbrabbitApplication in 16.941 seconds (JVM running for 22.495) org.springframework.boot.SpringApplication@4a163575 监听到applicationStartedEvent
自定义事件：必须继承抽象类ApplicationEvent
public class QuanEvent extends ApplicationEvent { /** * Create a new {@code ApplicationEvent}. * * @param source the object on which the event initially occurred or with * which the event is associated (never {@code null}) */ public QuanEvent(String source) { super(source); System.out.println("事件 "+source); } }
自定义监听器：监听自己定义的事件
public class QuanListenerQuanEvent implements ApplicationListener<QuanEvent> { @Override public void onApplicationEvent(QuanEvent event) { System.out.println("监听到QuanEvent"); } }
在完成springboot启动事件ApplicationStaredEvent中发布事件：
public class QuanListenerStartedEvent implements ApplicationListener<ApplicationStartedEvent> { @Override public void onApplicationEvent(ApplicationStartedEvent event) { event.getApplicationContext().publishEvent(new QuanEvent("hello")); } }
最后加上监听器的配置:
在spring.factories追加：
,com.quan.sbrabbit.Listener.QuanListenerQuanEvent
运行结果：
也可以使用注解进行监听器的编写（这时候只需要将监听器加载到bean容器里面就行，）
使用注解@EventListener
@Component public class QuanListenerQuanEvent { @EventListener public void onApplicationEvent(QuanEvent event) { System.out.println("监听到QuanEvent"); } }
监听事件的原理：
@FunctionalInterface public interface ApplicationListener<E extends ApplicationEvent> extends EventListener { /** * Handle an application event. * @param event the event to respond to */ void onApplicationEvent(E event); }
监听器触发机制：
SpringApplication-run 方法 public ConfigurableApplicationContext run(String... args){ SpringApplicationRunListeners listeners = getRunListeners(args); listeners.starting(); } 进入starting方法到SpringApplicationRunListener类 void starting() { for (SpringApplicationRunListener listener : this.listeners) { listener.starting(); } } 遍历所有的SpringApplicationRunListener 再进入starting：来到EventPublishingRunListener类： @Override public void starting() { this.initialMulticaster.multicastEvent(new ApplicationStartingEvent(this.application, this.args)); } 调用广播器发送 进入multicastEvent方法属于这个类：SimpleApplicationEventMulticaster @Override public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) { ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event)); Executor executor = getTaskExecutor(); //获得线程池 for (ApplicationListener<?> listener : getApplicationListeners(event, type)) {//获取对当前event感兴趣的监听器列表 if (executor != null) { executor.execute(() -> invokeListener(listener, event)); } else { invokeListener(listener, event); } } } 进入getApplicationListeners方法到类AbstractApplicationEventMulticaster protected Collection<ApplicationListener<?>> getApplicationListeners( ApplicationEvent event, ResolvableType eventType) { Object source = event.getSource();//获得事件来源 其实source就是SpringApplication
原文：https://www.cnblogs.com/java-quan/p/13588285.html