[FIX] 既存のデータは削除できないようにしました。

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

@@ -133,6 +133,8 @@ public class CourseServiceImpl implements CourseService {
 		System.out.println("***********************ここでエラー1");
 		if (userEntity.getCourseEntity().getCourseId() == courseId) {
 			return "selected";
+		} else if (courseId <= 6) {
+			return "original";
 		}
 		System.out.println("***********************ここでエラー2");
 		allocationRepository.deleteByCourseId(courseId);

src/main/java/com/example/demo/app/presentation/controller/CourseController.java

@@ -141,6 +141,10 @@ public class CourseController {
 
 			return TransitionTargetPageNameKeyword.REDIRECT + TransitionTargetPageNameKeyword.COURSE;
 
+		} else if (condition.equals("original")) {
+			model.addAttribute("message", "既存のデータは削除できません");
+
+			return TransitionTargetPageNameKeyword.REDIRECT + TransitionTargetPageNameKeyword.COURSE;
 		} else if (condition.equals("ok")) {
 			return TransitionTargetPageNameKeyword.REDIRECT + TransitionTargetPageNameKeyword.COURSE;
 		} 

src/main/resources/templates/select_course.html

@@ -36,7 +36,8 @@
 						aria-controls="'collapse' + ${course.courseId}">
 						<span th:text="${course.courseName}"></span>
 					</button>
-					<p style="width: 120px;"><button type="button" class="btn btn-danger w-100"
+					
+					<p th:if="${course.courseId > 6}" style="width: 120px;"><button type="button" class="btn btn-danger w-100"
 							th:attr="data-course-id=${course.courseId}" onclick="deleteCourse(this)">削除</button></p>
 				</h2>
 				<div th:id="'collapse' + ${course.courseId}" class="accordion-collapse collapse"