Thank you so much for the great lecture ㅠㅠ I only used the old style Spring, but I really liked the new technology called Spring Boot. It's a new world... I only knew how to use it by putting a library inside the Spring xml file... bundling the war file, uploading the Tomcat server on the ec2 server, uploading Apache... bundling it with an ssl certificate... but Jar is really a new world ㅠㅠㅠ!! I didn't know how time passed!