Spring boot CommandLineRunner example

In Spring boot projects, CommandLineRunner interface is used to run a code block only once in application’s lifetime – after application is initialized.

CommandLineRunner can be used in two ways:

1. Using CommandLineRunner as @Component

   ApplicationStartupRunner class implements CommandLineRunner interface.

   import org.apache.commons.logging.Log;
   import org.apache.commons.logging.LogFactory;
   import org.springframework.boot.CommandLineRunner;
   import org.springframework.stereotype.Component;
   
   @Component
   public class ApplicationStartupRunner implements CommandLineRunner 
   {
       protected final Log logger = LogFactory.getLog(getClass());
    
       @Override
       public void run(String... args) throws Exception {
           logger.info("ApplicationStartupRunner run method Started !!");
       }
   }
   

2. Implement CommandLineRunner in @SpringBootApplication

   CommandLineRunner interface is implemented on Application class, so override the run() here itself.

   import org.apache.commons.logging.Log;
   import org.apache.commons.logging.LogFactory;
   import org.springframework.boot.CommandLineRunner;
   import org.springframework.boot.SpringApplication;
   import org.springframework.boot.autoconfigure.SpringBootApplication;
   
   @SpringBootApplication
   public class Application implements CommandLineRunner 
   {
   	protected final Log logger = LogFactory.getLog(getClass());
   	
       public static void main( String[] args )
       {
       	SpringApplication.run(Application.class, args);
       }
       
       @Override
       public void run(String... args) throws Exception {
       	logger.info("ApplicationStartupRunner run method Started !!");
       }
   }