[CTJUG Forum] Re: Hibernate guru's

[Enrico Goosen]

I came across this solution while searching the Hibernate forum: http://hansonchar.blogspot.com/2005/06/why-use-beanlib-with-hibernate.html   Beanlib, enables you to clone an object graph, and you can configure it to do a deep clone or shallow clone. I struggled to get it working, with limited documentation, but was very pleased once I got it working.   Here’s some code:   /**      * Performs a deep clone of a Project      *      * @param projectId of Project to clone      * @param user the new Project owner      * @return projectId of new Project      */     public long clone(long projectId, User user) throws HibernateException {         Session session = HibernateUtil.getSession();         Project clonedProject = null;         try{             Project project = (Project)session.get(Project.class, projectId );             DetailedBeanPopulatable vetoer = new MyVetoer(session);             HibernateBeanReplicator replicator = new Hibernate3BeanReplicator().initDetailedBeanPopulatable(vetoer);             clonedProject = (Project)replicator.copy(project);             clonedProject.setName(project.getName()+" [CLONE]");             clonedProject.setUserByUserCreated(user);             clonedProject.setUserByUserModified(user);             clonedProject.setDateCreated(new Date(System.currentTimeMillis()));             clonedProject.setLastModified(new Date(System.currentTimeMillis()));             session.save(clonedProject);             session = ManagedSessionContext.unbind(HibernateUtil.getSessionFactory());             session.getTransaction().commit();         } catch (Throwable ex){             HibernateUtil.rollbackTransaction(session);             throw new HibernateException(ex);         }         return clonedProject.getId();     }   …   public class MyVetoer implements DetailedBeanPopulatable {     private SessionFactory sessionFactory;         public MyVetoer(Session session) {         this.sessionFactory = session.getSessionFactory();     }         public boolean shouldPopulate(String propertyName,             Object fromBean, Method readerMethod,             Object toBean, Method setterMethod) {         //Don’t want to create new instances of User and Keywordsource        //So populating the id field will stop Hibernate from saving a new instance.        //it’s a bit messy but it works…         if (fromBean instanceof User || fromBean instanceof Keywordsource)             return true;                 if (Collection.class.isAssignableFrom(readerMethod.getReturnType()))             return true;         // Skip populating if it is an identifier property.         Class c = readerMethod.getDeclaringClass();                 if (Enhancer.isEnhanced(c)) {             // figure out the pre-enhanced class             c = c.getSuperclass();         }         ClassMetadata classMetaData = sessionFactory.getClassMetadata(c);                 return !classMetaData.getIdentifierPropertyName().equals(propertyName);     } }   From: CTJUG-Forum@googlegroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Noel Grandin Sent: 05 May 2006 05:00 PM To: CTJUG-Forum@googlegroups.com Subject: [CTJUG Forum] Re: Hibernate guru's   You probably have a recursive loop in there somewhere. Me personally, I would create copy constructors on the necessary classes, and make them do deep copies of their children, thus traversing the tree implicitly. It puts the information where it belongs (in each class) and has far less issues than cloning. On 5/4/06, Enrico Goosen < [EMAIL PROTECTED]> wrote: This is becoming really tricky.   When I detach the object from the session, I can't access the rest of the objects in the graph, since they may not have been loaded (Lazy loading). I tried cloning as I traverse the non-detached object graph, making sure to change the IDs of the clones and not the original, and it appeared to be working, then I got an OutOfMemory error. *DOH*   A solution must be close…   From: CTJUG-Forum@googlegroups.com [mailto:CTJUG-Forum@googlegroups.com] On Behalf Of Noel Grandin Sent: 04 May 2006 01:14 PM To: CTJUG-Forum@googlegroups.com Subject: [CTJUG Forum] Re: Hibernate guru's   Yeah, you have to detach, or it maintains extra data in the CGLIB-constructed objects that tell it that the object has an identity in the database. Not sure what the "null" value is for primitive longs. You could use the unsaved-value attribute in the mapping file to tell hibernate explicitly that "-1" means "new object". Hibernate is not particularly friendly to swing GUI apps. Since they don't have defined request/response cycle it can get quite icky. Be careful of the long conversion pattern, it is easy to leak memory that way. I open and close sessions everywhere I talk to hibernate, which is a little verbose, but stops leaks Sometimes I will pass the session object around inside a class. But I never store the session object on a field. On 5/4/06, Enrico Goosen <[EMAIL PROTECTED]> wrote: The plot thickens…   Is it really necessary to detach the object graph from the session? I'm using the session-per-conversation pattern (long conversation), because my Swing gui application doesn't work well Hibernate session-per-request pattern.   Setting the IDs to null is also a problem, because I'm using long (primitive type) for the IDs. When I set the ID to -1, I get a NonUniqueObjectException.   What to do…what to do…     From: CTJUG-Forum@googlegroups.com [mailto:CTJUG-Forum@googlegroups.com] On Behalf Of Noel Grandin Sent: 04 May 2006 10:09 AM To: CTJUG-Forum@googlegroups.com Subject: [CTJUG Forum] Re: Hibernate guru's   Hmmm, detaching the object will make it "new" from hibernate's point of view. Then if you set the IDs to null, and persist it, it should create a new object graph. But I'm not sure how you would make this recurse down an object graph. It would probably depend on what the cascade attribute in the mapping file was set to. On 5/4/06, Enrico Goosen < [EMAIL PROTECTED]> wrote: Is it possible to clone and persist an object graph in Hibernate? I've come across the org.hibernate.util.SerializationHelper which can be used to clone an object graph, but I don't think that it can be persisted, since its id's will be the same as the original object graph.   Any ideas?   Enrico Goosen Software Developer SAICOM TECHNOLOGY TEL:       +2721 417 1375 FAX:     +2721 417 1361 CEL:     +2783 305 5676 EMAIL: [EMAIL PROTECTED]         --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "CTJUG Forum" group. 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