SpringBoot CommandLineRunner run() method not being called

Question

I'm learning SpringBoot. My (trivial) problem is I can't get the run() method from the CommandLineRunner Interface to be called by SpringBoot. I'm using Java 8 , Eclipse Oxygen ,Maven and i'm running my project as a "Spring Boot App". Code is:

package com.clarivate.dataviewer;

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DvMain implements CommandLineRunner{

static Logger logger = LogManager.getRootLogger();

public static void main(String[] args) {
    logger.debug("DS1A in main()");
    //SpringApplication.run(DvMain.class, args);
    SpringApplication app = new SpringApplication(DvMain.class);
    //ConfigurableApplicationContext app = SpringApplication.run(DvMain.class, args);
    logger.debug("DS1B in main()");
    app.run(args);
}

@Override
public void run(String... args) throws Exception {
    // This does not get called
    logger.debug("DS4 this line is never printed");
}
}

The overridden run() method does not get called. I've tried creating a separate class that implements CommandLineRunner but same problem. The console trace is:

SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/C:/Users/44/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/C:/Users/44/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.10.0/log4j-slf4j-impl-2.10.0.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [ch.qos.logback.classic.util.ContextSelectorStaticBinder]
12:58:42.225 [main] DEBUG  - DS1A in main()
12:58:42.289 [main] DEBUG  - DS1B in main()

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.0.2.RELEASE)

2018-06-20 12:58:42.614  INFO 16924 --- [           main] com.clarivate.dataviewer.DvMain          : Starting DvMain on 44-TPD-A with PID 16924 (C:\workspace_oxyegen\dataviewer\target\classes started by 44 in C:\workspace_oxyegen\dataviewer)
2018-06-20 12:58:42.615  INFO 16924 --- [           main] com.clarivate.dataviewer.DvMain          : No active profile set, falling back to default profiles: default
2018-06-20 12:58:42.655  INFO 16924 --- [           main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@6b4a4e18: startup date [Wed Jun 20 12:58:42 BST 2018]; root of context hierarchy
2018-06-20 12:58:43.266  INFO 16924 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2018-06-20 12:58:43.279  INFO 16924 --- [           main] com.clarivate.dataviewer.DvMain          : Started DvMain in 0.988 seconds (JVM running for 1.684)
2018-06-20 12:58:43.294  INFO 16924 --- [       Thread-2] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@6b4a4e18: startup date [Wed Jun 20 12:58:42 BST 2018]; root of context hierarchy
2018-06-20 12:58:43.296  INFO 16924 --- [       Thread-2] o.s.j.e.a.AnnotationMBeanExporter        : Unregistering JMX-exposed beans on shutdown

I'm sure i've made a simple mistake but I just can't see it. Any help appreciated.

Answer 1

Firstly, the call is coming to your run method. But doesn't log anything because there are couple of issues with your logger. You can use System.out.println(...) to confirm this.

1. Change your Logger declaration as below.

   private static final Logger logger = LoggerFactory.getLogger(DvMain.class);
   

2. You are not using correct libraries. Use Logger from slf4j and not log4j

   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;