Creation timestamp and last update timestamp with Hibernate and MySQL

Answer 1

A good approach is to have a common base class for all your entities. In this base class, you can have your id property if it is commonly named in all your entities (a common design), your creation and last update date properties.

For the creation date, you simply keep a java.util.Date property. Be sure, to always initialize it with new Date().

For the last update field, you can use a Timestamp property, you need to map it with @Version. With this Annotation the property will get updated automatically by Hibernate. Beware that Hibernate will also apply optimistic locking (it's a good thing).

Answer 2

As data type in JAVA I strongly recommend to use java.util.Date. I ran into pretty nasty timezone problems when using Calendar. See this Thread.

For setting the timestamps I would recommend using either an AOP approach or you could simply use Triggers on the table (actually this is the only thing that I ever find the use of triggers acceptable).

Answer 3

Just to reinforce: java.util.Calender is not for Timestamps. java.util.Date is for a moment in time, agnostic of regional things like timezones. Most database store things in this fashion (even if they appear not to; this is usually a timezone setting in the client software; the data is good)

Answer 4

If you are using the JPA annotations, you can use @PrePersist and @PreUpdate event hooks do this:

@Entity
@Table(name = "entities")    
public class Entity {
  ...

  private Date created;
  private Date updated;

  @PrePersist
  protected void onCreate() {
    created = new Date();
  }

  @PreUpdate
  protected void onUpdate() {
    updated = new Date();
  }
}

or you can use the @EntityListener annotation on the class and place the event code in an external class.

Answer 5

You might consider storing the time as a DateTime, and in UTC. I typically use DateTime instead of Timestamp because of the fact that MySql converts dates to UTC and back to local time when storing and retrieving the data. I'd rather keep any of that kind of logic in one place (Business layer). I'm sure there are other situations where using Timestamp is preferable though.

Answer 6

Solution with native MySQL functionality: Update and create timestamps with MySQL Works fine with java and hibernate.

Answer 7

Taking the resources in this post along with information taken left and right from different sources, I came with this elegant solution, create the following abstract class

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.MappedSuperclass;
import javax.persistence.PrePersist;
import javax.persistence.PreUpdate;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@MappedSuperclass
public class AbstractTimestampEntity {

    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "created", nullable = false)
    private Date created;

    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "updated", nullable = false)
    private Date updated;

    @PrePersist
    protected void onCreate() {
    updated = created = new Date();
    }

    @PreUpdate
    protected void onUpdate() {
    updated = new Date();
    }
}

and have all your entities extend it, for instance:

@Entity
@Table(name = "campaign")
public class Campaign extends AbstractTimestampEntity implements Serializable {
...
}