@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(
    excludeFilters = {@Filter(
    type = FilterType.CUSTOM,
    classes = {TypeExcludeFilter.class}
), @Filter(
    type = FilterType.CUSTOM,
    classes = {AutoConfigurationExcludeFilter.class}
)}
)
public @interface SpringBootApplication {
    .........  
}

@ComponentScan是Spring FrameWork3.1版本开始引入的

@EnableAutoConfiguration：激活自动装配     @Enable->@Enable开头的（Enable开头的取个名字叫激活模式）

@SpringBootConfiguration:等价于@Configguration ->Configuration Class 注解

@Component的"派生性"

(阅读Spring注解编程模型：https://github.com/spring-projects/spring-framework/wiki/Spring-Annotation-Programming-Model
@Component就是下面@Service以及其他的元注解（Meta-Annotations）

@Component->@ComponentScan  
处理类 -> ConfigurationClassParser

扫描类 -> ClassPathBeanDefinitionScanner
　　　　　　　　ClassPathBeanDefinitionScanner
                  ClassPathScanningCandidateComponentProvider

    protected void registerDefaultFilters() {
        this.includeFilters.add(new AnnotationTypeFilter(Component.class));
           ........
    }

@Component
public @interface Service{
    ........
}

@Component
public @interface Controller{
    ........
}

@Component
public @interface Repository{
    ........
}

@Component
public @interface Configuration{
    ........
}

@Configuration
public class SpringAnnotationDemo {

    public static void main(String[] args) {
        // XML配置文件驱动    ClassPathXmlApplicationContext
        //Annotation驱动       （两者都是找BeanDefinition）
        AnnotationConfigApplicationContext  context = new AnnotationConfigApplicationContext();
        //注册一个Configuration class = SpringAnnotationDemo
        context.register(SpringAnnotationDemo.class);
        //上下文启动
        context.refresh();
        System.out.println(context.getBean(SpringAnnotationDemo.class));
    }
}

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

@SpringBootApplication标注当前一些功能
   @SpringBootApplication
        @SpringBootConfiguration
             @Configuration
                 @Component
上面就是@SpringBootApplication逐步等同于@Component，也进一步反映了下面所说的@Component的派生性，最终归宿还是Bean

    public static void main(String[] args) {
        new SpringApplicationBuilder(Application.class)
                .properties("server.port=0")  //0的意思是随机向操作系统要可用端口
                .run(args);
    }

public static void main(String[] args) {
        SpringApplication springApplication = new SpringApplication(Application.class);
        Map<String,Object> proprities = new LinkedHashMap<>();
        proprities.put("server.port","0");
        springApplication.setDefaultProperties(proprities);

　　     ConfigurableApplicationContext context = springApplication.run(args);

　　　　 System.out.println(context.getBean(Application.class));

}

 

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication springApplication = new SpringApplication(Application.class);
        Map<String,Object> proprities = new LinkedHashMap<>();
        proprities.put("server.port","0");
        springApplication.setDefaultProperties(proprities);
        //设置为非web应用
        springApplication.setWebApplicationType(WebApplicationType.NONE);
        ConfigurableApplicationContext context = springApplication.run(args);
        System.out.println(context.getBean(Application.class));
        //输出当前Spring Boot应用的ApplicationContext的类名
        System.out.println("当前Spring应用的上下文的类："+context.getClass().getName());
    }

}

WebApplicationType.REACTIVE：Spring WebFlux
　　　　DispatcherHandler
　　　　spring-boot-starter-webflux 存在

WebApplicationType.SERVLET：Spring MVV
　　　　Spring-boot-starter-web 存在

WebApplicationType.NONE：非Web类型
　　　　Servlet   不存在
　　　　Spring Web上下文 ConfigurableWebApplicationContext 不存在
　　　　　　spring-boot-starter-web  不存在（这个地方就是pom文件里的）
　　　　　　spring-boot-starter-webflux  不存在
（根据下面的存在与否SpringApplication就能知道是什么环境[环境一说是在2.2.1版本：StandardEnvironment]）

public class SpringEventListenerDemo {

    public static void main(String[] args) {
        GenericApplicationContext context = new GenericApplicationContext();
        //添加事件监听器
//        context.addApplicationListener(new ApplicationListener<ApplicationEvent>() {
//            @Override
//            public void onApplicationEvent(ApplicationEvent event) {
//                System.err.println("监听事件："+event);
//            }
//        });

        //添加自定义监听器
        context.addApplicationListener(new ClosedListener());

        //启动spring应用上下文
        context.refresh();

        //两个事件，一个是ContextRefreshedEvent，一个是PayloadApplicationEvent
        //Spring应用上下文发布时间
        context.publishEvent("HelloWorld");//发布一个HelloWorld内容的事件
        //一个是我自己的是事件
        context.publishEvent(new MyEvent("HelloWorld 2019"));

        //关闭应用上下文
        context.close();
    }

    private static class ClosedListener implements ApplicationListener<ContextClosedEvent>{

        @Override
        public void onApplicationEvent(ContextClosedEvent event) {
            System.out.println("关闭上下文时间"+event);
        }
    }

    private static class MyEvent extends ApplicationEvent{


        public MyEvent(Object source) {
            super(source);
        }
    }

}

ContextRefreshedEvent
　　ApplicationContextEvent
　　　　ApplicationEvent
refresh（）->finishRefresh() ->publishEvent(new ContextRefreshedEvent(this))

ContextClosedEvent

　　ApplicationContextEvent

　　　　ApplicationEvent

refresh（）->finishRefresh() ->publishEvent(new ContextRefreshedEvent(this))

@EnableAutoConfiguration
public class SpringBootEventDemo {
    public static void main(String[] args) {
        new SpringApplicationBuilder(SpringBootEventDemo.class)
                .listeners(event -> {
                    System.out.println("监听到事件：" + event.getClass().getName());
                })//增加监听器
                .run(args);//运行
    }
}

SpringBoot事件监听器

org.springframework.context.ApplicationListener=org.springframework.boot.ClearCachesApplicationListener,org.springframework.boot.builder.ParentContextCloserApplicationListener,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