cannot be cast to hibernate.HibernateSession while run jsp

Question

I was trying to write my first Hibernate project. But I got an exception.

java.lang.ClassCastException: org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction cannot be cast to hibernate.HibernateSession

This is how I code session methods.

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;

public class HibernateSession {

    static Connection.NewHibernateUtil hibernateutil;
    static SessionFactory sessionfactory;
    static Session session;
    static Transaction transaction;

    private HibernateSession() {
    }

    public static HibernateSession getHSConnection() {
        if (transaction == null) {
            session = Connection.NewHibernateUtil.getSessionFactory().openSession();
            transaction = session.beginTransaction();
        }
        return (HibernateSession) transaction;
    }

    public static void closeHSConnection() {
        if (transaction != null) {
            session.flush();
            transaction.commit();
        }
        session.close();
    }
}

Are there any errors in this code?

score 3 · Accepted Answer · answered May 15 '18 at 22:01

3

You can't cast an object to your class when it is an instance of a completely different class (JDBCTransaction)

  return (HibernateSession) transaction; // this is the error

answered May 15 '18 at 22:01

Joakim Danielson

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score 1 · Answer 2 · answered May 16 '18 at 07:27

In this answer Joakim's explanation is perfect.

You have a couple of options depending on what you really want.

If you need HibernateSession object (an object from the class which you have written), change the return statement of getHSConnection() to,
```
return new HibernateSession();
```

Or if you need the newly created org.hibernate.Transaction then change your method

public static Transaction getHSConnection() {
    ...
    return transaction;
}

But I suggest that you should return neither of those. Return the org.hibernate.Session. Because,

I don't see any instance variables in your class HibernateSession so there's no point of returning an object of a class with static variables and methods, in fact that should be the reason why your have a private constructor for that class.
You can always get the current transaction using the method beginTransaction(). the javadoc says,

...If a new underlying transaction is required, begin the transaction. Otherwise continue the new work in the context of the existing underlying transaction...

So I suggest you change your method like this,

public static Session getHSConnection() {
    ...
    return session;
}

and when you need to commit the transaction,

Session s = HibernateSession.getHSConnection();
s.beginTransaction().commit();

Remember it all depends on your requirement.

cannot be cast to hibernate.HibernateSession while run jsp

2 Answers2