系统监听器

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import org.springframework.boot.context.event.ApplicationStartedEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.lang.NonNull;

/**
 * @author itning
 * @date 2020/4/29 16:59
 */
public class FirstListener implements ApplicationListener<ApplicationStartedEvent> {
    @Override
    public void onApplicationEvent(@NonNull ApplicationStartedEvent event) {
        System.out.println("FirstListener");
    }
}

直接子类

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AbstractSubProtocolEvent, 
ApplicationContextEvent, 
BrokerAvailabilityEvent, 
PayloadApplicationEvent, 
RequestHandledEvent, 
TestContextEvent

源码：

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setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));

在spring.factories文件中

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org.springframework.context.ApplicationListener=\
org.springframework.boot.ClearCachesApplicationListener,\
org.springframework.boot.builder.ParentContextCloserApplicationListener,\
org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,\
org.springframework.boot.context.FileEncodingApplicationListener,\
org.springframework.boot.context.config.AnsiOutputApplicationListener,\
org.springframework.boot.context.config.ConfigFileApplicationListener,\
org.springframework.boot.context.config.DelegatingApplicationListener,\
org.springframework.boot.context.logging.ClasspathLoggingApplicationListener,\
org.springframework.boot.context.logging.LoggingApplicationListener,\
org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener

同样三种配置方式：

  1. 关键代码：springApplication.addListeners(new FirstListener(), new SecondListener());

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    import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import top.itning.springboottest.config.FirstApplicationContextInitializer;
import top.itning.springboottest.listener.FirstListener;
import top.itning.springboottest.listener.SecondListener;

/**
* @author itning
*/
@SpringBootApplication
public class SpringbootTestApplication {
   public static void main(String[] args) {
       //SpringApplication.run(SpringbootTestApplication.class, args);
       SpringApplication springApplication = new SpringApplication(SpringbootTestApplication.class);
       springApplication.addInitializers(new FirstApplicationContextInitializer());
       springApplication.addListeners(new FirstListener(), new SecondListener());
       springApplication.run(args);
}
}

  2. 只需要在应用配置文件中application.yml配置：context.initializer.classes=xxx.xxx.xxx.XX

    查看原理：org.springframework.boot.context.config.DelegatingApplicationListener

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    context:
  listener:
    classes: xxx.xxx.xxx.XX

  3. resources目录新建META-INF文件夹并且新建文件：spring.factories

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    org.springframework.context.ApplicationListener=xxx.xxx.xxx.XX