Problem with Hibernate.createBlob() in 3.5-Final

alexvp · **Joined:** Tue Dec 15, 2009 4:56 pm **Posts:** 2

Hi, all!
I am currently worked on an project that saves binary files to DB (PostgreSQL 8.3, Hibernate 3.5).

I have next code:

Domain object:

Code:

@Entity
@Table(name="ITEM")
public class Item {

   @Id @GeneratedValue
   @Column(name="ITEM_ID")
   private Long id = null;
   
   @Lob
   @Column(name="BLOB_LOCATOR")
   private Blob blobLocator;
   
   public Item() {}
   
   public Long getId() {
      return id;
   }
      
   public Blob getBlobLocator() {
      return blobLocator;
   }
   
   public void setBlobLocator(Blob blobLocator) {
      this.blobLocator = blobLocator;
   }
   
}

Snippet from DAO class:

Code:

Session session = HibernateUtil.getSessionFactory().getCurrentSession();

session.beginTransaction();
Item item = new Item();
item.setBlobLocator(Hibernate.createBlob(new byte[100], session));
session.saveOrUpdate(item);
session.getTransaction().commit();

When i try run it, throws exception:

Code:

Exception in thread "main" java.lang.ClassCastException: $Proxy9 cannot be cast to org.hibernate.engine.jdbc.LobCreationContext
   at org.hibernate.Hibernate.getLobCreator(Hibernate.java:420)
   at org.hibernate.Hibernate.getLobCreator(Hibernate.java:416)
   at org.hibernate.Hibernate.createBlob(Hibernate.java:412)

If instead createBlob(byte[], Session) used createBlob(byte[]), it's work fine! But method createBlob(byte[]) deprecated in Hibernate 3.5.
When instead HibernateUtil.getSessionFactory().openSession() i use HibernateUtil.getSessionFactory().getCurrentSession(), that's work fine.

Everybody know how to solve this problem? Thank you for you help!

saltnlight5 · **Posted:** Thu Sep 02, 2010 12:07 pm

I see the same issue as well.

The deprecated method still works though. The Hibernate.createBlob(blobBytes, session) fails for session that uses ThreadLocalSessionContext. It doesn't seem like the session wrapped ThreadLocalSessionContext (which produced by sessionFactory.getCurrentSession()) has a way to let you unwrap it, which is needed by the by Hibernate.createBlob(blobBytes, session). Now if we work with JPA, it works because EnityManager.unwrap(Session.class) gives you back a real session object. Obviously if you use sessionFactory.openSession() you won't have the problem, but then it's not a context managed session. :(

I think this is Hibernate's bug and they should fix this.

The current solution to continue use a ThreadLocalSessionContext wrapped session to create a Blob is either use the deprecated method, or use a direct JDBC connection object to build your own. Like this:

Code:

            
      session.doWork(new Work() {      
         @Override
         public void execute(Connection connection) throws SQLException {
            Blob blob = connection.createBlob();
                                // get dataBytes
            java.sql.Blob blob.setBytes(1, dataBytes);
            // now you have a blob to use         
         }
      });
      

alexvp · **Joined:** Tue Dec 15, 2009 4:56 pm **Posts:** 2

Thank you for your reply!

I find another solution - don't use java.sql.Blob at all :-)). I currently use byte[] property type and javassist bytecode instrumentation for field's lazy loading instead.

saltnlight5 · **Posted:** Fri Sep 10, 2010 7:45 am

I have filed a JIRA issue to track this

http://opensource.atlassian.com/project ... e/HHH-5550

albertpaul68 · **Joined:** Tue Jan 25, 2011 6:52 am **Posts:** 1

I believe this would also affect sessions obtained from ManagedSessionContext.currentSession() and JTASessionContext.currentSession(), which return org.hibernate.classic.Session, because that does not extend LobCreationContext either.

In 3.6, session.getLobHelper().createBlob( bytes ), should be used instead.

Zemian, could you give 3.6.0 a try?