Print Hello World before Spring boot application start-CodePudding

Hello guys I want to ask if its possible to execute the print before the spring boot application start?

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


@SpringBootApplication
public class SampleApplication implements CommandLineRunner {

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

    @Override
    public void run(String... args) {
        System.out.print("I would be appear in log first before spring application starts");
    }

}

My problem of my code it will display the print after the spring boot application start

Current Output

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.5.2)

2021-09-26 06:13:53.267  INFO 10352 --- [           main] c.s.d.SampleApplicationTests      : Starting SampleApplicationTests using Java 11.0.11 on User-Desktop with PID 10352 (started by ???)
2021-09-26 06:13:53.277  INFO 10352 --- [           main] c.s.d.Sample




ApplicationTests      : No active profile set, falling back to default profiles: default
2021-09-26 06:13:54.879  INFO 10352 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFAULT mode.
2021-09-26 06:13:55.051  INFO 10352 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 148 ms. Found 9 JPA repository interfaces.
2021-09-26 06:13:57.118  INFO 10352 --- [           main] o.hibernate.jpa.internal.util.LogHelper  : HHH000204: Processing PersistenceUnitInfo [name: default]
2021-09-26 06:13:57.299  INFO 10352 --- [           main] org.hibernate.Version                    : HHH000412: Hibernate ORM core version 5.4.32.Final
2021-09-26 06:13:57.563  INFO 10352 --- [           main] o.hibernate.annotations.common.Version   : HCANN000001: Hibernate Commons Annotations {5.1.2.Final}
2021-09-26 06:13:58.268  INFO 10352 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-09-26 06:14:03.062  INFO 10352 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
2021-09-26 06:14:03.094  INFO 10352 --- [           main] org.hibernate.dialect.Dialect            : HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect
2021-09-26 06:14:08.430  INFO 10352 --- [           main] o.h.e.t.j.p.i.JtaPlatformInitiator       : HHH000490: Using JtaPlatform implementation: [org.hibernate.engine.transaction.jta.platform.internal.NoJtaPlatform]
2021-09-26 06:14:08.453  INFO 10352 --- [           main] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'
2021-09-26 06:14:15.216  INFO 10352 --- [           main] c.s.d.SampleApplicationTests      : Started SampleApplicationTests in 22.607 seconds (JVM running for 24.991)
I would be appear in log first before spring application starts

CodePudding user response：

Why don't you just print the log in main method before run invocation?

@SpringBootApplication
public class SampleApplication implements CommandLineRunner {

    public static void main(String[] args) {
        System.out.print("I would be appear in log first before spring application starts");
        SpringApplication.run(SampleApplication.class, args);
    }

    @Override
    public void run(String... args) {
    }

}

run method is a method from Spring Boot so everything you do there is done after Spring Boot's start.

CodePudding user response：

If by before the spring boot application start you mean application context startup, then yes, the easiest (for singletons beans, anyway) being to annotate your method with @PostConstruct.

@PostConstruct
    public void init() {
        //do something
    }

Check for the @PostConstruct for e.g here.