I listened to the Java roadmap and then took this Spring introduction course after the Java Advanced 2nd part. Somehow, I ended up writing this Spring introduction course review after listening to the Spring Core Principles Basic Part, http Web Basic Knowledge, jpa Utilization 1st Part, and Spring MVC 1st Part. Since the intention of the course was to introduce Spring rather than explain the concepts or principles of Spring, it was more difficult for me to study because of my personality that tries to understand everything one by one. I tried to understand the flow of the operation even though I didn’t understand the principles, and thanks to the good explanation, I was able to get a general idea. Although many things were unfamiliar, I think it is a course that is necessary when starting Spring. Learning the principles first when you don’t know what you will do or what you will learn later requires patience and can sometimes be frustrating. On the other hand, when you start knowing that you will learn this in advance, the joy of realizing that what you learned in the introduction course was this principle, and that the principle was this is different and gives you the desire to learn the next thing quickly, which is good. While listening to the Java course, I heard the polymorphism story that Mr. Kim Young-han mentioned countless times throughout the Spring course, and the Java course was really helpful. And I think the dependency injection was a vague story when I took the Java Advanced course, but after listening to the Spring course, I really feel it. Thank you for making a good course.