How to Do One to Many Mapping in JPA For this scenario

[rahulranjanmca@gmail.com]

I have a class
public class ExamCategoryDTO {
@Id
private Long id;
@OneToMany(mappedBy = "examCategoryDTO", targetEntity = ExamNameDTO.class, fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private List<ExamNameDTO> examNameList;
}

And another class
public class ExamNameDTO {
@Id
private Long id;
@Column(name="EXAM_CATEGORY_ID")
private Long examCategoryId;
@ManyToOne
@JoinColumn(name = "EXAM_CATEGORY_ID")
private ExamCategoryDTO examCategoryDTO;
}

If i do like this it gives error saying that EXAM_CATEGORY_ID is alearady mapped. I need to know the way to save ExamNameDTO without ExamCategoryDTO and i want to sent the Foreign key in ExamNameDTO manuaaly and Some times i want to save thru ExamCategoryDTO and in that case it will have ExamCategoryDTO as list. I want to do bothways. How can i do that. Please help

[r035198x]

Remove the

@Column(name="EXAM_CATEGORY_ID")
private Long examCategoryId;

part.

The

@ManyToOne
@JoinColumn(name = "EXAM_CATEGORY_ID")
private ExamCategoryDTO examCategoryDTO;

part already does that for you.

Don't name your entities using DTO.