JPA ConstraintViolationException forgein键的值为null

Question

I migration to JPA persistent with Hibernate. I test with two Entity and when persist a entity, I receive the exception on constrains violation for the value null of the forgein key.

This is structure the table of database:

CREATE TABLE AZIENDA
(AZN_ID INTEGER NOT NULL PRIMARY KEY GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1),
...

CREATE TABLE AGENTE
(AGN_ID INTEGER NOT NULL PRIMARY KEY GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1),
    AGN_IDAZN INTEGER NOT NULL,
...
CONSTRAINT FK_AGN_AZN FOREIGN KEY (AGN_IDAZN) REFERENCES AZIENDA (AZN_ID) ON DELETE CASCADE);

The Entity:

@Entity
@Table(name="AZIENDA")
public class Azienda {    
    @Column(name="AZN_ID")    
    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Integer id;
...
@Entity
@Table(name="AGENTE")
public class Agente {   
    @Column(name="AGN_ID")    
    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Integer id;

    @Column(name="AGN_IDAZN")
    @JoinColumn(name="FK_AGN_AZN", referencedColumnName="AZN_ID")
    @ManyToOne()
    // @ManyToOne(optional=true, cascade=CascadeType.PERSIST)
    @Transient
    private Azienda azienda;
...

First all retrieve the object 'Azienda' from database, after instance a new 'Agente' entity and set the property 'azienda', when create and persist a new entity 'Agente', I receive ConstraintViolationExcpetion The column 'AGN_IDAZN' can't containt the value null, but the instance 'Azienda' not is null.

Thanks!!

Answer 1

Try to remove @Transient annotation from azienda property of Agente class.

@Transient annotation means that entity fields are fields that do not participate in persistence and their values are never stored in the database.

Answer 2

I realized in a different way the functionality @Transient annotation... Thanks!!

This is the Entity changes:

@Entity
@Table(name="AGENTE")
public class Agente {   

    ...

    @JoinColumn(name="AGN_IDAZN", referencedColumnName="AZN_ID")
    @ManyToOne(cascade=CascadeType.PERSIST)
    private Azienda azienda;

    ...
 }