The ResourceBanner uses placeholders with the regular syntax ${variable.name} syntax.

There are only a few variables supported, which is fine; and some of them, such as the application version, is not resolved when starting the project from IDE (as opposed from the jar).

I wanted to use default values, for instance ${application.version:dev}; when I do that, the printed version becomes dev regardless of whether it's defined.

I reproduced the issue in unit tests in ResourceBannerTests, and I think it is due to the way we handle resolvers:

for (PropertyResolver resolver : getPropertyResolvers(environment, sourceClass)) {
    banner = resolver.resolvePlaceholders(banner);
}

If the first resolver fails to find the value, it outputs the default value and it's final.