I got Hibernate Exception when saving subcategory

Question

I am developing a j2ee project. In my Project I want to save a Product subcategory using Hibernate criteria.

This is my servlet code:

try {     
    if (req.getParameter("ccategory").equals("0")) {
        ProductCategory category = new ProductCategory();//saveing product category
        category.setName(req.getParameter("cname"));
        category.setStatus(status);
        HibernateSession.save(HibernateSession.getSession(), category);

    } else {

        ProductCategory category = HibernateSession.Load(ProductCategory.class, req.getParameter("ccategory"));
        ProductSubcategory productSubcategory = new ProductSubcategory();
        productSubcategory.setProductCategory(category);
        productSubcategory.setSubcategory(req.getParameter("cname"));
        productSubcategory.setStatus(status);
        HibernateSession.save(HibernateSession.getSession(), productSubcategory);
    }

    resp.sendRedirect("index.jsp");
} catch (Exception e) {
    e.printStackTrace();
}

this is my session code methods:

public class HibernateSession {

    public static Session getSession() {
        Session session = Connection.NewHibernateUtil.getSessionFactory().openSession();
        return session;
    }

    public static void save(Session session, Object ob) {
        Transaction transaction = session.beginTransaction();
        session.save(ob);
        session.flush();
        transaction.commit();
        session.close();
    }
}

but when saving the subcategory I got an error.

org.hibernate.HibernateException: illegally attempted to associate a proxy with two open Sessions

org.hibernate.HibernateException: illegally attempted to associate a proxy with two open Sessions
    at org.hibernate.proxy.AbstractLazyInitializer.setSession(AbstractLazyInitializer.java:123)
    at org.hibernate.engine.internal.StatefulPersistenceContext.reassociateProxy(StatefulPersistenceContext.java:568)
    at org.hibernate.engine.internal.StatefulPersistenceContext.reassociateIfUninitializedProxy(StatefulPersistenceContext.java:533)
    at org.hibernate.event.internal.ProxyVisitor.processEntity(ProxyVisitor.java:49)
    at org.hibernate.event.internal.AbstractVisitor.processValue(AbstractVisitor.java:124)
    at org.hibernate.event.internal.WrapVisitor.processValue(WrapVisitor.java:125)
    at org.hibernate.event.internal.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:76)
    at org.hibernate.event.internal.AbstractSaveEventListener.visitCollectionsBeforeSave(AbstractSaveEventListener.java:372)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:273)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:194)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:125)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:209)
    at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:55)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:194)
    at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:49)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
    at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:711)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:703)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:698)
    at hibernate.HibernateSession.save(HibernateSession.java:28)
    at Servlet.category.category_save.doPost(category_save.java:55)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)

Answer 1

Actually, you need to add session.close() method after loading a category.

ProductCategory category = HibernateSession.Load(ProductCategory.class, 
req.getParameter("ccategory")); 
session.close(); 

The problem occurred due to two session which get created. After loading a category you haven't close the session. So, in above code there is define the solution.