Spring Boot is a popular Java framework for building web applications. One of its powerful features is the ability to execute tasks at application startup. In this article, we will discuss how to create a custom Spring Boot command-line runner and use it to execute tasks when the application starts up.

Creating a Custom Spring Boot Command-Line Runner

To create a custom command-line runner in Spring Boot, we need to create a class that implements the CommandLineRunner interface. This interface has a single method called run, which takes an array of Strings as its parameter.

import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

@Component
public class CustomCommandLineRunner implements CommandLineRunner {

    @Override
    public void run(String... args) throws Exception {
        // add your task here
    }
}

In the above code, we have created a class called CustomCommandLineRunner that implements the CommandLineRunner interface. We have also annotated it with @Component to make it a Spring bean. The run method is where we can add our custom task that we want to execute at application startup.

Executing Tasks at Application Startup

To execute our custom task at application startup, Spring Boot will automatically call the run method of all beans that implement the CommandLineRunner interface. In our case, the CustomCommandLineRunner bean will be executed.

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

@SpringBootApplication
public class MyApp {

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

In the above code, we have a typical Spring Boot main class. We have used the SpringApplication.run method to start the application. When this method is called, Spring Boot will automatically find all beans that implement the CommandLineRunner interface and execute their run method.

To summarize, creating a custom Spring Boot command-line runner is a powerful way to execute tasks at application startup. By implementing the CommandLineRunner interface and adding our custom task in the run method, we can ensure that our task is executed when the application starts up.

Whether you need to initialize data, set up a database connection, or perform any other task at application startup, a custom command-line runner can help you achieve this in Spring Boot. By following the simple steps outlined in this article, you can easily create your custom runner and execute your tasks at application startup.