如何通过Hibernate合并为字段设置默认NULL值

Question

@Entity
@Table(name = "account")
public class PrepaidAccount implements Account, Serializable {

protected Integer pre_notif_interval;

public Integer getPreNotifInterval() {
        return pre_notif_interval;
    }

    public void setPreNotifInterval(Integer pre_notif_interval) {
        this.pre_notif_interval = pre_notif_interval;
    }

I need to set NULL (default value against this field).

How do I do it?

From the service where I call, I have some integer value setting working fine -

account.setPreNotifInterval(2);
em.persist(account);

Db schema is -

 `pre_notif_interval` tinyint(1) DEFAULT NULL;

Answer 1

1 Object value is null by default

2 Set field value explicitly protected Integer pre_notif_interval = null;

3 Use Listener like this to set default values:

public class EntityListener {

    @PrePersist
    void prePersistActions(PrepaidAccount account) {
        account.setPreNotifInterval(null);
    }

    @PreUpdate
    void preUpdateActions(PrepaidAccount account) {
        //some code
    }
}

and then

@Entity
@Table(name = "account")
@EntityListeners(EntityListener.class)
public class PrepaidAccount implements Account, Serializable {

    protected Integer pre_notif_interval;

    public Integer getPreNotifInterval() {
        return pre_notif_interval;
    }

    public void setPreNotifInterval(Integer pre_notif_interval) {
        this.pre_notif_interval = pre_notif_interval;
    }
}

Answer 2

In order the database will use the default value, that column shouldn't be specified during INSERT (or a special DEFAULT keyword shoud be used). Unfortunately JPA does not support neither approach. So a native SQL should be sent, which can be done using FluentJPA :

default PrepaidAccount insertWithDefaults(String required1,
                                          int required2) {
    FluentQuery query = FluentJPA.SQL((PrepaidAccount p) -> {
        INSERT().INTO(viewOf(p, PrepaidAccount ::getRequired1, Person::getRequired2));
        VALUES(row(required1, required2));

        // RETURNING(p); //PostgreSQL

        // Person inserted = INSERTED(); //SQL Server
        // OUTPUT(inserted);
    });

    // works in MySQL, H2
    int nOfUpdated = query.createQuery(getEntityManager()).executeUpdate();
    if (nOfUpdated <= 0)
        return null;

    query = FluentJPA.SQL((PrepaidAccount p) -> {
        SELECT(p);
        FROM(p);
        WHERE(p.getId() == LAST_INSERT_ID());
    });

    PrepaidAccount prepaid = query.createQuery(getEntityManager(), PrepaidAccount.class)
                                              .getSingleResult();

    return prepaid;
}

Note that returning the inserted row or id is vendor specific.