✅ Visitor Pattern add new operations to existing object structures without modifying those classes 👉🏻 separate algorithms(operations) from the objects on which they operate 👀 Shap...

✅ Presentation Layer check parameter from front end ✅ MockMVC use Mock(fake data) to test MVC To test controller, make service and repository a mock data How to use? need tw...

✅ Business Logic (1) As a cafe manager, create products (2) product number should be created automatically 📌 Business for Product Service @Transactional(readOnly = true) @RequiredArgsConst...

✅ Linux file system: ext2, 3, 4 ✅ Rules of files in linux 1️⃣ Files do not have extensions unless, you want to add an extension on purpose if you add an extension it becomes part of ...

⭐️ @SpringBootTest 🆚 @JpaDataTest @SpringBootTest 🆚 @WebMvcTest @Transactional(readOnly=true) optimistic lock 🆚 pessimistic lock CQRS: separate Command(CUD) and Query(Read) ✅ Business...

✅ Strategy Pattern make a lot of algorithms encapsulate them and make them interchangeable at runtime, 갈아끼우기 client will use the common interface only actual behavior can vary according...

✅ Mediator mediator object control how the objects interact objects communicate through mediator 👎🏻 before: objects communicate directly with each other, tight coupling 👍🏻 after ...

✅ Command Pattern encapsulate the request decouple invoker(호출자) and reciever(수신자) 👍🏻 when request logic changes, invoker code will not change ✅ Diagram 👀 Command pattern example ✔️ In...

⭐️ QueryDSL ✅ Production code @Repository public interface ProductRepository extends JpaRepository<Product, Long> { /** * select * * from product * where selling_sta...

✅ Product Entity @Entity @Getter @NoArgsConstructor(access = AccessLevel.PROTECTED) public class Product extends BaseEntity { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) pr...