I had some trial and error while using the updated version of Spring than in class. If I didn't have background knowledge, I would have given up in the middle, but I was able to find everything quickly by searching! Especially, I solved all the things that broke because there was no Event Manager at the end by myself before looking at the supplementary materials. Haha At the time, I was a little dissatisfied, but my heart melted when you explained everything in the last supplementary materials. Thanks to this, I was able to learn more about REST API, and I think it was a lecture that helped my development skills a lot. Thank you for your hard work and thank you~