EntityManager.find behavior with an object containing 2 id as primary key

Question

I'm starting to step into the Java world and I'm having troubles to understand this.

I'm using JPA to interact with my database with JPQL.

I have a persistent class like this one :

@Entity
@Table(name="C_A_T")
@NamedQuery(name="CAT.findAll", query="SELECT c FROM CAT c")
public class CAT implements Serializable {
    private static final long serialVersionUID = 1L;
    @EmbeddedId
    private CATPK id;
    private String offer;
    @Temporal(TemporalType.DATE)
    @Column(name="MODIF_DATE")
    private Date modifDate;


    public CAT() {}
    public CATPK getId() {return id;}
    public void setId(CATPK id) {this.id = id;}
    public String getOffer() {return offer;}
    public void setOffer(String offer) {this.offer = offer;} 
    public Date getModifDate() {return modifDate;}
    public void setModifDate(Date modifDate) {this.modifDate= modifDate;}
    /* ... */
}

The class CATPK represents a primary key of an instance of CAT :

@Embeddable
public class CATPKimplements Serializable {
    //default serial version id, required for serializable classes.
    private static final long serialVersionUID = 1L;
    @Column(name="ID_CAT")
    private String idCAT;
    @Column(name="ID_DEMANDE")
    private String idDemande;

    public CATPK() {}
    public String getIdCAT() {return this.idCAT;}
    public void setIdCAT(String idCAT) {this.idCat= idCat;}
    public String getIdDemande() {return this.idDemande;}
    public void setIdDemande(String idDemande) {this.idDemande = idDemande;}
    /* ...*/
}

So basicly, the primay key is made of 2 different ID.

Now, sometimes, before inserting a CAT in my database I checked if it is not already in the C_A_T table :

EntityManagerFactory emf = Persistence.createEntityManagerFactory("cie");
em = emf.createEntityManager();
em.getTransaction().begin();
// inCAT is an instance of CAT on which there is a complete primary key CATPK (made of 2 id)
CAT CATinDB = em.find( CAT.class, inCAT.getId() );
if (null == CATinDB)
  em.persist(inCAT); // CAT created
em.getTransaction().commit();
em.close();

Now, the problem is that the line em.find( CAT.class, inCAT.getId() ); doesn't return null when it should.

For instance, CATinDB can contain a row when I actually have no rows with the right idCAT and idDemande.

So will find consider that it is found with only one id of the catPK matching ?

In the end, I changed the line :

if (null == CATinDB)

into :

if (null == CATinDB || CATinDB.getId().getIdCAT() != inCAT.getId().getIdCAT() || CATinDB.getId().getIdDemande() != inCAT.getId().getIdDemande())

Not really sure why find wasn't returning null when I had no records matching the 2 id.

that's where you look at the JPA provider log and see the SQL invoked. — Neil Stockton, Sep 15 '16 at 12:32
How can I do that ? I'm using intelliJ. I got a persistence.xml file but I don't see where to go from there — Ellone, Sep 16 '16 at 08:25
persistence.xml usually specifies the JPA provider. Whether it does or not, you can easily work out which one you're using from CLASSPATH and the class of the instance of "emf". So you look in the docs for that provider and then look in the log. aka "debugging" — Neil Stockton, Sep 16 '16 at 08:32
This post can help where it explains how it can be achieved. http://stackoverflow.com/questions/17042987/composite-primary-key-in-jpa — mhasan, Sep 17 '16 at 19:17

score 0 · Accepted Answer · answered Oct 12 '16 at 09:55

0

Actually, I just needed to restart my weblogic server. Looks like the data source is not dynamically updated when I update the database.

answered Oct 12 '16 at 09:55

Ellone

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EntityManager.find behavior with an object containing 2 id as primary key

1 Answers1