java - 保存子类别时出现 Hibernate 异常

Question

我正在开发一个j2ee项目。在我的项目中，我想使用 Hibernate 标准保存产品子类别。

这是我的 servlet 代码:

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();
}

这是我的 session 代码方法:

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();
    }
}

但是在保存子类别时出现错误。

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

实际上，您需要在加载类别后添加 session.close() 方法。

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

该问题是由于创建了两个 session 而发生的。加载类别后，您尚未关闭 session 。因此，在上面的代码中定义了解决方案。