"Applying Object-Oriented Ideology to Lectures" Mr. Kim Young-han's lecture is not just a lecture that puts the concept of "DB access technology in Spring Boot" into your head as an implementation. This lecture creates an interface called "DB access technology in applications" in the students' heads. And the students get "JDBC", an implementation that implements that interface in a Java environment. Therefore, students who take this lecture do not need to study from the beginning even if they change the framework to Node-based Nest.js while using Java-based Spring. Since they already have a solid interface in their heads, they only need to put in an implementation for that environment after a short period of learning. I listened to this lecture and understood it. Why do companies say that they don't need engineers who are fascinated by a certain framework and only know how to implement it? In this era where technology changes rapidly every year, I felt that developers who have a good overall interface are more important than having a perfect implementation (of course it's important, lol..). That's probably why big companies value CS knowledge. While listening to this lecture, I, who had only thought of all concepts as implementations in the Java environment, had a big realization. "Why didn't I think of programming in an object-oriented way when I always used an object-oriented language?" I would like to express my deepest gratitude to Kim Young-han, who helped me in my development process. + If you are wondering whether you should take this lecture as well after taking the JPA lecture like me, definitely take it. However, if you have never worked on a project using Spring Boot, I recommend that you first take any topic. As I said earlier, this lecture is a process of putting the abstract concept of interface into your head, so it may be difficult to understand at first. If you listen to it after experiencing it once as a project, you will be able to enjoy the lecture with exclamations of "Ah, so this is how it works~"