At last, Sir Terry, we must walk together.
XClacks is a Servlet 3.0 filter adding the http header X-Clacks-Overhead: GNU Terry Pratchett to all responses.
Please see this The Guardian article for information about the origins and purpose of that header.
Add this jar to your classpath. You may also need to configure servlet filter classpath scanning in your framework/embedded web server:
Add @ServletComponentScan("io.github.buckcri.xclacks"), for example when declaring @SpringBootApplication:
import org.springframework.boot.web.servlet.ServletComponentScan
@SpringBootApplication
@ServletComponentScan("io.github.buckcri.xclacks")
class MySpringBootApplication
XClacks is available on Maven Central.