Spring Boot 自定义事件

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：

1. 自定义事件，继承 ApplicationEvent
2. 定义监听器，实现 ApplicationListener 或者通过 @EventListener 注解到方法上
3. 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