Http11NioProtocol is the non-blocking IO (NIO) connector for Tomcat.

Tomcat 8 typically uses the http-nio protocol unless specifically configured to use the blocking I/O (BIO) protocol (Http11Protocol). Therefore, even if you haven't explicitly configured NIO in your project, Tomcat itself is using it by default.

Try:

server.tomcat.protocol=org.apache.coyote.http11.Http11Protocol

This would force the use of the blocking IO connector if you want to switch away from NIO.