Hi,
I'm having a problem with Hibernate so I prepared the following test case to reproduce it easier.
I have 2 entities (Usuario and Grupo) with a OneToMany bidirectional relationship.
I'm doing some inserts followed by a query (checking if the insert worked).
I can retrieve the entity but can't follow the relationship:
Code:
Usuario u = (Usuario) em.createQuery("select u from Usuario u").getResultList().get(0);
System.out.println(u.toString()); // OUTPUT: "Usuario[id=22]"
System.out.println(u.getGrupoCollection()); // OUTPUT: "null"
Checking the database I can see that the inserts worked.
If I run the same query again (finish the execution and start it again without the updates) both print outs work:
Code:
Usuario u = (Usuario) em.createQuery("select u from Usuario u").getResultList().get(0);
System.out.println(u.toString()); // OUTPUT: "Usuario[id=22]"
System.out.println(u.getGrupoCollection()); // OUTPUT: "[Grupo[id=22]]"
I am manually deleting all records from database before the test case (only before inserts).
Both having the same id is just a coincidence (I've checked the database).
I have to finish the application and run it again. If I do the same query twice in the same runtime both return null for u.getGrupoCollection().
The database system is Postgres.
I'm new to JPA/Hibernate, so I am probably doing something wrong, but no idea what.
The entire code follows. Sorry if it is a lot of code, but I was afraid of keeping something important out.
Code:
public class Main {
public static EntityManagerFactory emf = Persistence.createEntityManagerFactory("RaphaelPU");
public static EntityManager em = emf.createEntityManager();
public static void main(String[] args) {
EntityTransaction tx = em.getTransaction();
try {
tx.begin();
Usuario usuario = new Usuario();
em.persist(usuario);
Grupo grupo = new Grupo();
grupo.setUsuarioId(usuario);
em.persist(grupo);
tx.commit();
} finally {
if (tx.isActive()) {
tx.rollback();
System.out.println("Bad news!");
}
}
Usuario u = (Usuario) em.createQuery("select u from Usuario u").getResultList().get(0);
System.out.println(u.toString());
System.out.println(u.getGrupoCollection());
}
}
Code:
@Entity
@Table(name = "usuario")
@NamedQueries({@NamedQuery(name = "Usuario.findAll", query = "SELECT u FROM Usuario u")})
public class Usuario implements Serializable {
@Id
@Basic(optional = false)
@Column(name = "id")
@SequenceGenerator(name="id", sequenceName="usuario_id_seq")
@GeneratedValue(strategy=GenerationType.AUTO ,generator="id")
private Integer id;
@OneToMany(cascade = CascadeType.ALL, mappedBy = "usuarioId")
private List<Grupo> grupoCollection;
public Usuario() {
}
public Usuario(Integer id) {
this.id = id;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public List<Grupo> getGrupoCollection() {
return grupoCollection;
}
public void setGrupoCollection(List<Grupo> grupoCollection) {
this.grupoCollection = grupoCollection;
}
@Override
public int hashCode() {
int hash = 0;
hash += (id != null ? id.hashCode() : 0);
return hash;
}
@Override
public boolean equals(Object object) {
if (!(object instanceof Usuario)) {
return false;
}
Usuario other = (Usuario) object;
if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
return false;
}
return true;
}
@Override
public String toString() {
return "Usuario[id=" + id + "]";
}
}
Code:
@Entity
@Table(name = "grupo")
@NamedQueries({@NamedQuery(name = "Grupo.findAll", query = "SELECT g FROM Grupo g")})
public class Grupo implements Serializable {
@Id
@Basic(optional = false)
@Column(name = "id")
@SequenceGenerator(name="id", sequenceName="grupo_id_seq")
@GeneratedValue(strategy=GenerationType.AUTO ,generator="id")
private Integer id;
@JoinColumn(name = "usuario_id", referencedColumnName = "id")
@ManyToOne(cascade = CascadeType.ALL)
private Usuario usuarioId;
public Grupo() {
}
public Grupo(Integer id) {
this.id = id;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Usuario getUsuarioId() {
return usuarioId;
}
public void setUsuarioId(Usuario usuarioId) {
this.usuarioId = usuarioId;
}
@Override
public int hashCode() {
int hash = 0;
hash += (id != null ? id.hashCode() : 0);
return hash;
}
@Override
public boolean equals(Object object) {
if (!(object instanceof Grupo)) {
return false;
}
Grupo other = (Grupo) object;
if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
return false;
}
return true;
}
@Override
public String toString() {
return "Grupo[id=" + id + "]";
}
}
Thanks,
Gustavo
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