[FIXED] Correct way of saving JPA entities in Spring Webflow: detached entity passed to persist

Issue

What is the correct method of dealing with situation like this:

I have a flow with 4 steps, each step is mapped to its entity class and is joined on one parent entity (ParentEntity is joined to each StepNEntity with one-to-one relationship). When proceeding to next step, current step gets saved to DB.

@Entity
public class ParentEntity {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column(name = "id", nullable = false)
  private Integer id;

  @OneToOne(mappedBy = "parentEntity")
  private Step1 step1;

  @OneToOne(mappedBy = "parentEntity")
  private Step2 step2;

  ...
}

@Entity
public class Step1 {

  @MapsId
  @OneToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "parent_id")
  private ParentEntity parentEntity;

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column(name = "id", nullable = false)
  private Integer id;

  ...
}

@Entity
public class Step2 {

  @MapsId
  @OneToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "parent_id")
  private ParentEntity parentEntity;

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column(name = "id", nullable = false)
  private Integer id;

  ...
}

I have no problems with saving ParentEntity with Step1 to DB with repository.save(). On second step when I try

parentEntity.setStep2(step2); // step2 is a model in my flow view
parentRepository.save(parentEntity); // produces org.hibernate.PersistentObjectException: detached entity passed to persist:

Similarly I get exception if I try

step2.setParentEntity(parentEntity);
step2Repository.save(step2);

Solution

My issue was in annotation @MapsId which I added by mistake. After manually setting ParentEntity and removing said annotation my code works.

Answered By - pcenta
Answer Checked By - Willingham (JavaFixing Volunteer)