How to start H2 TCP server on Spring Boot application startup?

Question

I'm able to start the H2 TCP server (database in a file) when running app as Spring Boot app by adding following line into the SpringBootServletInitializer main method:

@SpringBootApplication
public class NatiaApplication extends SpringBootServletInitializer {
    public static void main(String[] args) {
        Server.createTcpServer().start();
        SpringApplication.run(NatiaApplication.class, args);
    }
}

But if I run the WAR file on Tomcat it doesn't work because the main method is not called. Is there a better universal way how to start the H2 TCP server on the application startup before beans get initialized? I use Flyway (autoconfig) and it fails on "Connection refused: connect" probably because the server is not running. Thank you.

Answer 1

This solution works for me. It starts the H2 server if the app runs as Spring Boot app and also if it runs on Tomcat. Creating H2 server as a bean did not work because the Flyway bean was created earlier and failed on "Connection refused".

@SpringBootApplication
@Log
public class NatiaApplication extends SpringBootServletInitializer {

    public static void main(String[] args) {
        startH2Server();
        SpringApplication.run(NatiaApplication.class, args);
    }

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        startH2Server();
        return application.sources(NatiaApplication.class);
    }

    private static void startH2Server() {
        try {
            Server h2Server = Server.createTcpServer().start();
            if (h2Server.isRunning(true)) {
                log.info("H2 server was started and is running.");
            } else {
                throw new RuntimeException("Could not start H2 server.");
            }
        } catch (SQLException e) {
            throw new RuntimeException("Failed to start H2 server: ", e);
        }
    }
}

Answer 2

Yup, straight from the documentation, you can use a bean reference:

<bean id = "org.h2.tools.Server"
        class="org.h2.tools.Server"
        factory-method="createTcpServer"
        init-method="start"
        destroy-method="stop">
<constructor-arg value="-tcp,-tcpAllowOthers,-tcpPort,8043" />

There's also a servlet listener option that auto-starts/stops it.

That answers your question, but I think you should probably be using the embedded mode instead if it's deploying along with your Spring Boot application. This is MUCH faster and lighter on resources. You simply specify the correct URL and the database will start:

jdbc:h2:/usr/share/myDbFolder

(straight out of the cheat sheet).