SpringBoot: Create document in mongodb on startup if not exists

Question

I have a small service on SpringBoot and Mongodb as a DB. I need to be able create a small collection with one document ( very basic: id, name, status) on startup. An analog of sql create table if not exists, but for mongo. How do I do that? I tried to initialize values in the document attributes, but it didn't help. Currently, collection and the document appear only if I use API to add it.

Answer 1

You may want to use something like ApplicationRunner or CommandLineRunner which can be defined as a bean.

Example:

@SpringBootApplication
public class MyApplication {

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

    @Bean
    public CommandLineRunner initialize(MyRepository myRepository) {

        return args -> {
            // Insert elements into myRepository 
        };
    }
}

Both CommandLineRunner and ApplicationRunner are functional interfaces, so we can use a lambda for them. Spring Boot will execute them at the startup of the application.