Insert multiple rows to MySQL with JPA - spring-boot

Question

I am a newbie to spring boot. I have two entities: course1 and course2 with each having a field code, for course code. I have been able to generate select form fields due to entries on couse1 database table so that input to course2 will be selected. However, whenever I make a selection on the form and post, all the selected course codes will enter a single field on course2 database table instead of each entering a separate row. Hence, my problem is, I want to insert multiple rows into a database table using JPA. Following is what I did and will be grateful if any body helps
Course1 entity:
`
#NoArgsConstructor
#AllArgsConstructor
#Setter
#Getter
#Entity
#Table(name = "course_one")
public class CourseOne {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "course_one_id")
private Long courseOneId;
#Column(name = "course_code")
private String code;
#OneToOne(mappedBy = "courseOne")
private CourseTwo courseTwo;
`
Course1 entity contains more fields describing each course though.
Course2 entity:
`
#NoArgsConstructor
#AllArgsConstructor
#Setter
#Getter
#Entity
#Table(name="course_two")
public class CourseTwo{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "course_two_id")
private Long courseTwoId;
private String code;
#OneToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
#JoinColumn(name = "course_one_id")
private CourseOne courseOne;
`
Course2 repository
`
public interface CourseTwoRepository extends CrudRepository<CourseTwo, Long> {
}
`
At the service layer, the method I used to insert into the database table for course2 entity is:
`
public List<CourseTwo> saveCourseTwo(CourseTwo courseTwo) {
return(List<CourseTwo>) courseTwoRepo.saveAll(List.of(courseTwo));
}
`
This is my form:
<form action="#" th:action="#{/saveCourseTwo}" th:object="${courseTwo}" method="post">
<div class="overflow-scroll" style="border: 2px; height:dashed; height:300px; width:800px">
<div class="table-responsive">
<table class="table table-sm table-striped table-hover" style="width: 100%">
<thead class="green white-text">
<tr>
<th>Select</th>
<th>Code</th>
<th>Title</th>
<th>Units</th>
</tr>
</thead>
<tbody>
<tr th:each="select : ${listCourseOne}">
<td><input type="hidden" th:value="${select.courseOneId}" name="courseOne"/></td>
<td><input type="checkbox" class="form-check-input" name="code" th:value="${select.code}" />
<td th:text="${select.code}"></td>
<td th:text="${select.title}"></td>
<td th:text="${select.units}"></td>
</tr>
</tbody>
</table>
</div>
</div>
<button type="submit" class="btn btn-success">Save</button>
</form>
However, the method inserts all the selected course codes into a single field. I will be happy if anyone helps.
I also tried to create wrapper multiple instances of CourseTwo as follows:
List<CourseTwo> lisOfCourse =new ArrayList<>(courseTwo);
List<CourseTwo> courseTwoList = new ArrayList<>();
for(int i=0; i<lisOfCourse.size(); i++){
CourseTwo courseTwo1 = new CourseTwo();
courseTwo1.setCourseTwoId(courseTwo1.courseTwoId());
courseTwo1.setCode(courseTwo1.getCode());
courseTwoList.add(courseTwo1);
}
return (List<CourseTwo>) courseTwoRepo.saveAll(courseTwoList);
However, I get the following error: No primary or single unique constructor found for interface java.util.List