Adding entity doesn't refresh parent's collection

问题

the question and problem is pretty simple, though annoying and I am looking for a global solution, because it's application-wide problem for us.

The code below is really not interesting but I post it for clarification!

We use PostgreSQL database with JPA 2.0 and we generated all the facades and entities, of course we did some editing but not much really.

The problem is that every entity contains a Collection of its children, which however (for us only?) is NOT updated after creation a children element. The objects are written to database, you can select them easily, but what we really would like to see is the refreshed collection of children in parent object.

Why is this happening? If we (manually) refresh the entity of parent em.refresh(parent) it does the trick but it would mean for us a lot of work in Facades I guess. But maybe there is no other way?

Thanks for support!

/* EDIT */

I guess it has to be some annotation problem or cache or something, but I've already tried

@OneToMany(mappedBy = "idquestion", orphanRemoval=true, fetch= FetchType.EAGER)

and

@Cacheable(false)

didn't work properly.

/* EDIT */

Some sample code for understanding.

Database level:

CREATE TABLE Question (
        idQuestion SERIAL,
        questionContent VARCHAR,    
    CONSTRAINT Question_idQuestion_PK PRIMARY KEY (idQuestion)
);

CREATE TABLE Answer (
        idAnswer SERIAL,
        answerContent VARCHAR,
        idQuestion INTEGER,
    CONSTRAINT Answer_idAnswer_PK PRIMARY KEY (idAnswer),
    CONSTRAINT Answer_idQuestion_FK FOREIGN KEY (idQuestion) REFERENCES Question(idQuestion)
);

Than we have generated some Entities in Netbeans 7.1, all of them look similar to:

@Entity
@Table(name = "question", catalog = "jobfairdb", schema = "public")
@XmlRootElement
@NamedQueries({ BLAH BLAH BLAH...})
public class Question implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @Basic(optional = false)
    @NotNull
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    @Column(name = "idquestion", nullable = false)
    private Integer idquestion;
    @Size(max = 2147483647)
    @Column(name = "questioncontent", length = 2147483647)
    private String questioncontent;
    @OneToMany(mappedBy = "idquestion", orphanRemoval=true) 
    private Collection<Answer> answerCollection;

Getters... setters...

We use (again) generated facades for them, all implementing AbstractFacade like:

public abstract class CCAbstractFacade<T> {
    private Class<T> entityClass;

    public CCAbstractFacade(Class<T> entityClass) {
        this.entityClass = entityClass;
    }

    protected abstract EntityManager getEntityManager();

    public void create(T entity) {
        getEntityManager().persist(entity);
    }

回答1:

The father entity is updated automatically if you use container managed transactions and you fetch the collection after the transaction is complete. Otherwise, you have to update yourself the collection.

This article explains in detail this behaviour: JPA implementation patterns: Bidirectional associations

EDIT:

The simplest way to use Container Managed Transactions is to have transaction-type="JTA" in persistence.xml and use Container-Managed Entity Managers.

回答2:

You seem to be setting the ManyToOne side, but not adding to the OneToMany, you have to do both.

In JPA, and in Java in general you must update both sides of a bi-directional relationship, otherwise the state of your objects will not be in sync. Not doing so, would be wrong in any Java code, not just JPA.

There is no magic in JPA that will do this for you. EclipseLink does have a magic option for this that you could set through a customizer (mapping.setRelationshipPartnerAttributeName()), but it is not recommended, fixing your code to be correct is the best solution.

See, http://en.wikibooks.org/wiki/Java_Persistence/Relationships#Object_corruption.2C_one_side_of_the_relationship_is_not_updated_after_updating_the_other_side

来源：https://stackoverflow.com/questions/12283654/adding-entity-doesnt-refresh-parents-collection

标签

postgresql

jpa

jpa-2.0

eclipselink