Allow a programatically configured banner to override the default banner

[mmoayyed]

Using Spring Boot v4 M3 and JDK 25, I have a simple app that does this:

        new SpringApplicationBuilder()
            .banner(new MyBanner())
            // other stuff happens here
            .run(args);

As the documentation indicates, this is a fallback banner in case no banner is found as a resource. I'd like Spring Boot, if possible, to offer a way where the Banner implementation set here overrides any and all banner resources defined; IOW, let this be the primary banner and not the fallback. Perhaps introduce a new "Banner Mode" option?

The annoyance I am running into is that our app creates its own banner programmatically, and yet if we ship the app with a library that has its own banner.txt on the classpath (i.e. Spring Cloud) our banner is ignored and the resource takes over, which seems to me to be both "as intended" and somewhat odd.

If not, it would be good for the documentation to recommend how such a use case could be handled, so one could define and override their own "banner selection" logic, which at the moment is sort of hidden here:

private @Nullable Banner printBanner(ConfigurableEnvironment environment) {
		if (this.properties.getBannerMode(environment) == Banner.Mode.OFF) {
			return null;
		}
		ResourceLoader resourceLoader = (this.resourceLoader != null) ? this.resourceLoader
				: new DefaultResourceLoader(null);
		SpringApplicationBannerPrinter bannerPrinter = new SpringApplicationBannerPrinter(resourceLoader, this.banner);
		if (this.properties.getBannerMode(environment) == Mode.LOG) {
			return bannerPrinter.print(environment, this.mainApplicationClass, logger);
		}
		return bannerPrinter.print(environment, this.mainApplicationClass, System.out);
	}

Thank you.

[snicoll]

I believe this is is consistency with external configuration properties to take over what's defined in the code. If you define a @PropertySource with a key in your code, a value from application.properties would override it. Now I agree it's a bit odd that you can provide a Banner implementation programmatically and that would be trumped by ResourceBanner if it finds a matching resource on the classpath.

You could workaround this by setting the banner location to something that doesn't exist. I would also report this to Spring Cloud as I am not entirely sure it's intended that the banner is changed this way.

[snicoll]

We've discussed a few options and we're not quite sure what we'd like to do. Perhaps changing Banner so that an implementation can decide if override should happen. Or surface a BannerPrinter contract where the banner is given and an implementation could decide to swap it by something else.

In the meantime setting the property to a location that doesn't exist should do what you need.

[mmoayyed]

Thank you very much for the analysis and suggestions. I will see if I can work around this for the time being and will share this with the Spring Cloud folks as well.

[mmoayyed]

Just to bring this one home for the time being and for future passer-bys, the recommended approach works well with:

spring.banner.location=classpath:unknown.txt

Thank you for the hint.