spring boot在啟動過程中提供了一些事件的監(jiān)聽,這樣極大的方便了開發(fā)者拓展功能;

spring boot支持的事件類型:

事件列表

關鍵步驟:

1、實現(xiàn)接口ApplicationListener來創(chuàng)建自己的事件監(jiān)聽類;如:

@Component
public class ApplicationStartedEventListener implements ApplicationListener<ApplicationStartingEvent> {

    @Override
    public void onApplicationEvent(ApplicationStartingEvent applicationStartedEvent) {
        System.out.println("application starting .....");
    }
}

2、在啟動類中注冊,修改此前啟動類的代碼為:

@SpringBootApplication
public class SpringBootDemoApplication {
    public static void main(String[] args) {
        SpringApplication springApplication = new SpringApplication(SpringBootDemoApplication.class);
        springApplication.addListeners(new ApplicationStartedEventListener());

        springApplication.run(args);
    }
}

3、運行發(fā)現(xiàn)啟動前先打印

image.png

同樣的,為了省事,直接用lamda來實現(xiàn)其他幾個接口

@SpringBootApplication
public class SpringBootDemoApplication {

    public static void main(String[] args) {
        SpringApplication springApplication = new SpringApplication(SpringBootDemoApplication.class);
        springApplication.addListeners(new ApplicationStartedEventListener());

        springApplication.addListeners((ApplicationListener<ApplicationPreparedEvent>) event -> {
            System.out.println("application prepared event");
        });

        springApplication.addListeners((ApplicationListener<ApplicationReadyEvent>) event -> {
            System.out.println("application ready event");
        });

        springApplication.run(args);
    }
}

系統(tǒng)啟動時,執(zhí)行順序為:application starting > application prepared > application ready