how to globally define the naming convention with Jackson

Not sure how to do this globally but here's a way to do it at the JSON object level and not per each individual property:

@JsonNaming(PropertyNamingStrategy.SnakeCaseStrategy.class)
public class Foo {
    private String myBeanName;
    //...
}

would yield json:

{
    "my_bean_name": "Sth"
    //...
}

Actually, there was a really simple answer:

@Bean
public Jackson2ObjectMapperBuilder jacksonBuilder() {
    Jackson2ObjectMapperBuilder b = new Jackson2ObjectMapperBuilder();
    b.propertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
    return b;
}

I added it in my main like so:

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

    @Bean
    public Jackson2ObjectMapperBuilder jacksonBuilder() {
        Jackson2ObjectMapperBuilder b = new Jackson2ObjectMapperBuilder();
        b.propertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
        return b;
    }
}