hibernate/jpa how to store relation between one entity

Question

I would like to store hierarchical folders in database. F.e

@Entity
public class Folder {

int id
String name
Folder parentFolder

}

So if folder is in subfolder he should store information about parentFolder If Folder is in root/top folder, it dosnt have any parentFolder, so there will be null

How should I set hibernate using annotation to achive this?

My entity class:

@Entity
@Table(name="common__Role")
public class Role {

/** The id. */
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
public Long id;

/**
 * Parent Role id.
 */
@ManyToOne(fetch=FetchType.LAZY)
@JoinColumn(name="ROLE_ID")
public Role role;

/** The name. */
@Constraints.Required
public String name;

That is a @OneToMany nd a @ManyToOnerelation so you should handle this as such. — Jens
– Jens, Commented Oct 2, 2014 at 8:32

Xstian · Accepted Answer · 2014-10-02 14:20:07Z

2

This should be your Entity ..

@Entity
@Table("FOLDER")
public class Folder {

  @Id
  private long id;

  @Column(name="NAME")
  private String name;

  @ManyToOne(fetch=FetchType.LAZY,cascade = {CascadeType.PERSIST,CascadeType.MERGE })
  @JoinColumn(name="PARENT_ID")
  private Folder parentFolder;


  //Getter and Setter
}

Maybe you should follow this tutorial

How to persist ManyToOne

Folder f= new Folder();
f.setName("name");

Folder fParent = entityManager.find(Folder .class, 1L);
f.setParent(fParent);

entityManager.persist(f);

6 Comments

masterdany88 Over a year ago

I've tried, but Your solution didnt resolve problem. When I add another Folder, and I am choosing parentFolder there is no error. But there is no relation id in database between child-parent

Xstian Over a year ago

To save a relationship is needed a JoinColumn else does not work. You should add a column PARENT_ID. I suggest you a simple ManyToOne relationship using JPA.

masterdany88 Over a year ago

" You should add a column PARENT_ID" - did You mean database? I've done this, but there goes only nulls. There is no relation

Xstian Over a year ago

If you want persist everything you should add a cascade on relationship for the action that you needed. E.G. @ManyToOne(fetch=FetchType.LAZY,cascade = {CascadeType.PERSIST,CascadeType.MERGE })

masterdany88 Over a year ago

It didnt helped. Remember that I have relation inside one entity

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