[EDIT] 名前をもとに情報を取得する機能を追加しました。

src/main/java/com/example/demo/app/domain/service/CourseService.java

@@ -10,4 +10,5 @@ public interface CourseService {
 	
 	public CourseModel findById(Long courseId);
 	
+	public Long findByName(String courName);
 }

src/main/java/com/example/demo/app/domain/service/impl/CourseServiceImpl.java

@@ -25,4 +25,8 @@ public class CourseServiceImpl implements CourseService {
 	public CourseModel findById(Long courseId) {
 		return CourseModel.convertFrom(courseRepository.findByCourseId(courseId));
 	}
+	
+	public Long findByName(String courseName) {
+		return courseRepository.findByCourseName(courseName).getCourseId();
+	}
 }

src/main/java/com/example/demo/app/infra/repository/CourseRepository.java

@@ -10,5 +10,8 @@ public interface CourseRepository extends JpaRepository<CourseEntity, Long> {
 	@Query("SELECT c FROM CourseEntity c WHERE c.courseId = :courseId ")
 	public CourseEntity findByCourseId(Long courseId);
 	
+	@Query("SELECT c FROM CourseEntity c WHERE c.courseName = :courseName ")
+	public CourseEntity findByCourseName(String courseName);
+	
 	
 }