ThymeleafBannerAutoConfiguration.java

package ac.simons.wjax2016.starter;

import org.springframework.boot.autoconfigure.AutoConfigureBefore;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration;
import org.springframework.context.annotation.Configuration;
import org.thymeleaf.spring4.SpringTemplateEngine;

@Configuration
@ConditionalOnClass({SpringTemplateEngine.class, ThymeleafAutoConfiguration.class})
@AutoConfigureBefore(ThymeleafAutoConfiguration.class)
class ThymeleafBannerAutoConfiguration {
}

The questions was asked during my talk at Spring I/O 2016 (See: https://www.youtube.com/watch?v=wSWA63rZfGo), wether @AutoConfigureBefore will cause trouble if the auto configuration class in question isn't on the classpath: It depends!

Regarding the ThymeleafAutoConfiguration it won't cause any troubles for projects inherited from Spring Boot Parent, because ThymeleafAutoConfiguration is in there.
But if you depend on another starter, you must shield the application as I did in the 2nd version of the gist, by adding the AutoConfiguration classes to the ConditionalOnClass as well…

Have a look at the talk and the demo here http://info.michael-simons.eu/2016/06/01/talking-about-custom-spring-boot-starter-at-spring-io/