Hibernate - Callback methods

Callbacks Methods: It is often useful for the application to react to certain events that occur inside the persistence mechanism.


TypeDescription
@PrePersistExecuted before the entity manager persist operation is actually executed or cascaded. This call is synchronous with the persist operation.
@PreRemoveExecuted before the entity manager remove operation is actually executed or cascaded. This call is synchronous with the remove operation.
@PostPersistExecuted after the entity manager persist operation is actually executed or cascaded. This call is invoked after the database INSERT is executed.
@PostRemoveExecuted after the entity manager remove operation is actually executed or cascaded. This call is synchronous with the remove operation.
@PreUpdateExecuted before the database UPDATE operation.
@PostUpdateExecuted after the database UPDATE operation.
@PostLoadExecuted after an entity has been loaded into the current persistence context or an entity has been refreshed.

Example
@Entity
@EntityListeners(class=Audit.class)
public class Cat {
    @Id private Integer id;
    private String name;
    private Calendar dateOfBirth;
    @Transient private int age;
    private Date lastUpdate;
    //getters and setters

    /**
     * Set my transient property at load time based on a calculation,
     * note that a native Hibernate formula mapping is better for this purpose.
     */
    @PostLoad
    public void calculateAge() {
        Calendar birth = new GregorianCalendar();
        birth.setTime(dateOfBirth);
        Calendar now = new GregorianCalendar();
        now.setTime( new Date() );
        int adjust = 0;
        if ( now.get(Calendar.DAY_OF_YEAR) - birth.get(Calendar.DAY_OF_YEAR) < 0) {
            adjust = -1;
        }
        age = now.get(Calendar.YEAR) - birth.get(Calendar.YEAR) + adjust;
    }
}

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


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