Spring 官方文档翻译如下 ：
ApplicationContext 通过 ApplicationEvent 类和 ApplicationListener 接口进行事件处理。 如果将实现 ApplicationListener 接口的 bean 注入到上下文中，则每次使用 ApplicationContext 发布 ApplicationEvent 时，都会通知该 bean。 本质上，这是标准的观察者设计模式。
Spring的事件（Application Event）其实就是一个观察者设计模式，一个 Bean 处理完成任务后希望通知其它 Bean 或者说 一个Bean 想观察监听另一个Bean的行为。
Spring 事件只需要几步：
- 自定义事件，继承 ApplicationEvent
- 定义监听器，实现 ApplicationListener 或者通过 @EventListener 注解到方法上
- 定义发布者，通过 ApplicationEventPublisher
代码示例：
自定义event
/**
* 自定义事件
*
* @author lz
* @date 2019/8/13
*/
@EqualsAndHashCode(callSuper = true)
@Data
public class DemoEvent extends ApplicationEvent {
private String message;
public DemoEvent(Object source, String message) {
super(source);
this.message = message;
}
}
自定义监听器
编程式——>实现ApplicationListener 接口
/**
* 自定义监听
*
* @author lz
* @date 2019/8/13
*/
@Component
public class DemoListener implements ApplicationListener<DemoEvent> {
@Override
public void onApplicationEvent(DemoEvent event) {
System.out.println("自定义事件");
System.out.println(event);
}
}
注解式——> 添加@EventListener注解
/**
* 自定义监听
*
* @author lz
* @date 2019/8/13
*/
@Component
public class DemoListener2 {
@EventListener
public void onApplicationEvent(DemoEvent demoEvent) {
System.out.println("收到了：" + demoEvent.getSource() + "消息;时间：" + emoEvent.getTimestamp());
}
}
消息发布者
/**
* 自定义监听
*
* @author lz
* @date 2019/8/13
*/
@Component
public class DemoPublisher {
private final ApplicationContext applicationContext;
@Autowired
public DemoPublisher(ApplicationContext applicationContext) {
this.applicationContext = applicationContext;
}
public void publish(String message) {
applicationContext.publishEvent(new DemoEvent(this, message));
}
}
测试
/**
* 启动
*
* @author lz
* @date 2019/8/13
*/
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(DemoApplication .class, args);
run.publishEvent(new DemoEvent(DemoApplication .class, "随便"));
}
}
结果
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.7.RELEASE)
2019-08-13 10:39:19.611 INFO 13600 --- [ main] com.example.demo655.DemoApplication : Starting DemoApplication on DESKTOP-AQTLR8E with PID 13600 (E:\IdeaProjects6\demo655\target\classes started by ** in E:\IdeaProjects6\demo655)
2019-08-13 10:39:19.613 INFO 13600 --- [ main] com.example.demo655.DemoApplication : No active profile set, falling back to default profiles: default
2019-08-13 10:39:20.360 INFO 13600 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2019-08-13 10:39:20.374 INFO 13600 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2019-08-13 10:39:20.375 INFO 13600 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.22]
2019-08-13 10:39:20.450 INFO 13600 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2019-08-13 10:39:20.450 INFO 13600 --- [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 784 ms
2019-08-13 10:39:20.582 INFO 13600 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2019-08-13 10:39:20.700 INFO 13600 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2019-08-13 10:39:20.702 INFO 13600 --- [ main] com.example.demo655.DemoApplication : Started DemoApplication in 1.373 seconds (JVM running for 2.255)
自定义事件
DemoEvent(message=随便)
spring boot 系统启动事件
最后分享一下springboot提供的一些事件
image
系统启动时,执行顺序为:application starting > application prepared > application ready
