[FIXED] Run Spring-Enabled @Component Method on Tomcat Startup

Issue

My SpringMVC application runs in Tomcat. I have a Spring-enabled @Component with a method that needs to execute just once on Tomcat startup. It's a method to go into the Service/DAO layer and send an email.

Normally, the way to do a Tomcat Startup Java class call is in web.xml as a Servlet with load-on-startup (link).

<servlet>
    <servlet-name>StartupEmail</servlet-name>
    <servlet-class>com.app.StartupEmail</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>

But that Servlet won't have access to my Spring layer with dependencies.

public class StartupEmail extends HttpServlet {
..
}

I can also have Cron-based Scheduled Jobs in SpringMVC, but they are time-based rather than on Tomcat Startup.

@Component
public class StatusScheduleJob {
    @Autowired
    private MyService myService;

    @Scheduled(cron = "${statusjob.cron.expression}")
    public void changeStatuses() {
         myService.execute(); //...
    }
}

statusjob.cron.expression=0 0 * * * *

So is there a good solution here?

Solution

If I understand the problem, there are several options depending on when exactly the startup code needs to be executed:

• Javax @PostConstruct annotation on a bean
• Implementing the InitializingBean interface
• Implementing the ApplicationListener interface for ContextRefreshedEvent
• Implementing the Spring CommandLineRunner interface

Here are a few references to learn about these options and more:

• https://www.baeldung.com/running-setup-logic-on-startup-in-spring
• https://docs.spring.io/spring-boot/docs/current/api/org/springframework/boot/CommandLineRunner.html
• https://docs.oracle.com/javaee/7/api/javax/annotation/PostConstruct.html

Answered By - Thomas Portwood