Question

I’m doing a Web application using Spring 3.1.0.RELEASE, JSF 2.x, JPA 2 with Hibernate Provider, MySql 5.1.x. The application runs on Tomcat 7.X.

In my entities I have some date like last update date:

@Column(name = "last_update_date", insertable = false, updatable = false)
@Temporal(TemporalType.TIMESTAMP)
private Date lastUpdateDate;

For the moment I have a trigger that updates:

CREATE TRIGGER upd_site BEFORE UPDATE ON site
FOR EACH ROW SET NEW.last_update_date = CURRENT_TIMESTAMP();

It works fine, but I just notice that there is some callbacks methods in JPA http://www.objectdb.com/java/jpa/persistence/event

What is the best between JPA Events and the MySql’s triggers ?

Thanks.

Answer 1

I have used it both ways with Triggers in the DB and with JPA listeners, I have settled on the JPA listeners because:

• the only code talking to the database in JPA code so I don’t have to worry about the time stamp fields falling out of date. (If this changes in the future I can add triggers and change my mapped super calss)

• JPA listeners are less complex in the sense that I did not have to go creating lots of triggers in my database so I had less things to maintain. Since I am actively developing and changing the db structure as I go along its great not to have to go and update triggers as I rapidly iterate through the development.

• I have complete control over the database and made a rule for the db that every table was going to have a integer pkey, and an integer version, and that the time stamped tables would have insert_ts and update_ts columns these are universal rules in my db design so life is easy I have these two mapped superclases that make all my enitites simple to code since I extend from them.

@MappedSuperclass
public abstract class PersistableObject {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="pkey")
    private Integer pkey;

    @Version
    @Column(name="version")
    private Integer version;

    public Integer getPkey() {
        return this.pkey;
    }

    public Integer getVersion() {
        return this.version;
    }

    @Override
    public String toString() {
        return "Presistable Object: pkey=" + this.pkey + " Object: " + this.getClass().getName();
    }
}

and

@MappedSuperclass
public class TimeStampedPersistableObject extends PersistableObject {

    @Column(name = "insert_ts")
    @Temporal(TemporalType.TIMESTAMP)
    private Date    insertTimestamp;

    @Column(name = "update_ts")
    @Temporal(TemporalType.TIMESTAMP)
    private Date    updateTimestamp;

    @SuppressWarnings("unused")
    @PrePersist
    private void onInsert() {
        this.insertTimestamp = new Date();
        this.updateTimestamp = this.insertTimestamp;
    }

    @SuppressWarnings("unused")
    @PreUpdate
    private void onUpdate() {
        this.updateTimestamp = new Date();
    }


    public Date getInsertTimestamp() {
        return this.insertTimestamp;
    }


    public Date getUpdateTimestamp() {
        return this.updateTimestamp;
    }
}