CommandLineRunner接口具有什么功能呢?

CommandLineRunner接口的功能

CommandLineRunner接口为Spring Boot应用程序启动时运行一些代码
使用CommandLineRunner,可在应用程序启动时执行某些操作
    如初始化数据、加载配置或运行其他任务。

通过实现CommandLineRunner接口
   您可以轻松地将需要在应用程序启动时提前处理的代码、任务或操作集成到Spring Boot应用程序中
    如:
	 可使用CommandLineRunner接口来加载应用程序的配置文件、初始化数据源、创建Spring ApplicationContext等操作

CommandLineRunner的使用方式

方式1:
   @Component

方式2:
   @SpringBootApplication

方式3:
  声明一个实现了CommandLineRunner接口Bean

@Component实现CommandLineRunner接口的功能

@SpringBootApplication
public class Demo03Application {

    public static void main(String[] args) {
        System.out.println("step 1: The Service will start");
        SpringApplication.run(Demo03Application.class, args);
        System.out.println("step 5: The Service has started");
    }

}
@Component
@Order(1)
class Runner1 implements CommandLineRunner {

    @Override
    public void run(String... args) throws Exception {
        System.out.println("step 3: The Runner1 run...");
    }
}

@Component
@Order(2)
class Runner2 implements CommandLineRunner {

    @Override
    public void run(String... args) throws Exception {
        System.out.println("step 4: The Runner1 run...");
    }
}

2. @SpringBootApplication实现CommandLineRunner接口的功能

 
@SpringBootApplication
public class Demo03Application implements CommandLineRunner{

    public static void main(String[] args) {
        System.out.println("step 1: The Service will start");
        SpringApplication.run(Demo03Application.class, args);
        System.out.println("step 5: The Service has started");
    }

    @Override
    public void run(String... args) throws Exception {
        System.out.println("app start");
    }
}

3.@Bean实现CommandLineRunner接口的功能

@SpringBootApplication
public class SpringBootWebApplication extends SpringBootServletInitializer {

    public static void main(String[] args) throws Exception {
        SpringApplication.run(SpringBootWebApplication.class, args);
    }
 
    @Bean
    public ApplicationStartupRunner schedulerRunner() {
        return new ApplicationStartupRunner();
    }
}
public class ApplicationStartupRunner implements CommandLineRunner {
    protected final Log logger = LogFactory.getLog(getClass());
    @Override
    public void run(String... args) throws Exception {
        logger.info("Application Started !!");
    }
}