在springboot 容器啟動時，我們需要在啟動過程中做一些操作，比如啟動容器後，執行某些代碼。

spring 提供了監聽器，我們可以方便的實現這些操作。

在容器啟動開始時：

package com.neo.filter;

import org.springframework.boot.context.event.ApplicationStartingEvent;
import org.springframework.context.ApplicationListener;

public class ApplicationStartingEventListener implements
 
 ApplicationListener<ApplicationStartingEvent> {
    @Override
    public void onApplicationEvent(ApplicationStartingEvent arg0) {
        System.err.println("ApplicationStartingEventListener");
    }

}

在容器啟動完成後執行操作：

package com.neo.filter;

import org.springframework.boot.context.event.ApplicationStartedEvent;
 
import org.springframework.context.ApplicationListener;
import org.springframework.core.Ordered;

public class ApplicationStartedEventListener implements ApplicationListener<ApplicationStartedEvent>,Ordered {

    @Override
    public void onApplicationEvent(ApplicationStartedEvent ev) {
        System.out.println(
 
"ApplicationStartedEventListener1");
    }
    @Override
    public int getOrder() {
        return 1;
    }

}

如果需要有順序執行，我們可以實現Ordered接口，只越小，越先執行。

package com;


import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import com.neo.filter.ApplicationStartedEventListener;
import com.neo.filter.ApplicationStartedEventListener2;
import com.neo.filter.ApplicationStartingEventListener;

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication app=new SpringApplication(DemoApplication.class);
        app.addListeners(new ApplicationStartedEventListener());
        app.addListeners(new ApplicationStartingEventListener());
        app.addListeners(new ApplicationStartedEventListener2());
        app.run(args);
    }
}

springboot 容器啟動事件