Setting a bean value (column) automatically before persisting in Hibernate?

Is there a nice and elegant way to set a bean value (column) before Hibernate persists an entity? Basically I have a field called "modification_date". It's on a bunch of entities. Whenever one of these entities is updated/modified, I'd basically like that field set automatically.

I could write the code in the service layer to set the date every time the object is saved/updated manually...

I also ha开发者_如何转开发ve a Dao Layer. Every Dao extends from a support class that contains a save() method. I could just use reflection and set the value inside of this method. I could check to see if that class has a field with the name "modicationDate", and if it does, set it to new Date().

Is there a better way than this? Or is using my generic save() method the best approach? This is something I'd like to be robust and not have to worry about it ever again. I will be happy knowing that by simply making a "modificationDate" property that this will be taken care of for me automatically from this point on. Using the save() method seems like the best place, but if there's a better way, I'd like to become aware of it.

Checkout event listeners:

@Entity
@EntityListeners(class=LastUpdateListener.class)
public class Cat {
    @Id private Integer id;
    private String name;
    private Calendar dateOfBirth;
    @Transient private int age;
    private Date lastUpdate;

    @PostLoad
    public void calculateAge() {
        ...
    }
}

public class LastUpdateListener {
    /**
     * automatic property set before any database persistence
     */
    @PreUpdate
    @PrePersist
    public void setLastUpdate(Cat o) {
        o.setLastUpdate( new Date() );
    }
}