How to autogenerate created or modified timestamp field?

Question

My entity class:

@Entity
@Table(name = \"user\")
public class User implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
           


        

Answer 1

Since @PrePersist and @PreUpdate are ignored when Hibernate Session is used I've made a relatively simple solution using Interceptors:

1. Define an interface "Auditable":

   public interface Auditable {
     public void setUpdated_at(Date date);
     public void setCreated_at(Date date);
   }
   

2. Define a class "AuditableInterceptor"

   public class AuditableInterceptor extends EmptyInterceptor {
   
       private static final long serialVersionUID = -3557239720502671471L;
   
       @override
       public boolean onFlushDirty(Object entity,
               Serializable id,
               Object[] currentState,
               Object[] previousState,
               String[] propertyNames,
               Type[] types) {
   
           if (entity instanceof Auditable) {
               for (int i = 0; i < propertyNames.length; i++) {
                   if ("updated_at".equals(propertyNames[i])) {
                       currentState[i] = new Date();
                       return true;
                   }
               }
           }
           return false;
       }
   
       @override
       public boolean onSave(Object entity,
               Serializable id,
               Object[] state,
               String[] propertyNames,
               Type[] types) {
   
           if (entity instanceof Auditable) {
               for (int i = 0; i < propertyNames.length; i++) {
                   if ("created_at".equals(propertyNames[i])) {
                       state[i] = new Date();
                       return true;
                   }
               }
           }
           return false;
       }
   }
   

3. Specify the Interceptor when ever you open a new session (you'll likely have this in a utility class)

   sessionFactory.openSession(new AuditableInterceptor());
   // sessionFactory.openSession();
   

4. Implement the Auditable interface in your entities, e.g.

   @Entity
   public class Product implements Auditable {
   
       ...
       private Date created_at;
       private Date updated_at;
       ...
   
       public Product() {
       }
   
       ...
   
       @Temporal(javax.persistence.TemporalType.TIMESTAMP)
       public Date getCreated_at() {
           return created_at;
       }
   
       public void setCreated_at(Date created_at) {
           this.created_at = created_at;
       }
   
       @Temporal(javax.persistence.TemporalType.TIMESTAMP)
       public Date getUpdated_at() {
           return updated_at;
       }            @Override
   
       @Override
       public void setUpdated_at(Date updated_at) {
           this.updated_at = updated_at;
       }
       ...
   }
   

Notes:

1. This example expects the properties created_at and updated_at. For different names the method names have also to be adapted.
2. Type must be org.hibernate.type.Type!