I'm reading Spring Basics 3 times. When I first listened to it, I had just gotten rid of Java(?), so I didn't really understand the concept of object-oriented programming, and the instructor explained dependency injection and SOLID terms, so I just tried to make progress by slogging through the entire course. The second time I read it (I finished the curriculum up to the actual querydsl and listened to it again), I think I studied with the joy of thinking, "Oh, this is it..." Now that I've finished reading it for the third time, my thoughts are... I think the core of this lecture is in Section 1. Young-han is such a bright lecturer, so I always listen to him with a smile, but I think that the part where his eyes shine the most is when he teaches Section 1 of the Spring Basics. What is good object-oriented programming, How flexible Spring is from an object-oriented perspective And how it came to light in the world.. Now that I've let go of the reins by touching on the MVC pattern or API, I came back to read the basics for the third time after seeing myself become infinitely helpless while designing the architecture, And I have no regrets. Thank you, teacher, for guiding me in the direction I saw it twice or three times.. Come to think about it, I don't think I've ever seriously and deeply thought about Spring's object-oriented perspective. If you all listen to the basics lectures while thinking about polymorphism, you will definitely get a big root!