Where does the second open session come from in Hibernate?

Question

MySQL

Hello, there are two POJO classes.

public class PatienceEntity {
    private int id;
    private String fio;
    private Set disease;
    private Set analysis; //элементы сета типа AnalysisEntity 
}
public class AnalysisEntity {
    private int id;
    private TypeOfAnalysisEntity typeOfAnalys;
    private PatienceEntity patience;
}

As you can see from the code, each class has a reference to another class. Dao for these classes looks like this.
CrudDao - common parent for classes

public abstract class CrudDao <ID, T> {
    protected SessionFactory sessionFactory;


    void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    public CrudDao(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    public void create(T o) {
        Session session;
        try {
            session = sessionFactory.getCurrentSession();
        } catch (HibernateException ex) {
            session = sessionFactory.openSession();
        }

        Transaction transaction = null;

        transaction = session.beginTransaction();

        session.save(o);
        transaction.commit();

    }

    public T read(ID id, Class classToRead) {
        Session session;
        try {
            session = sessionFactory.getCurrentSession();
        } catch (HibernateException ex) {
            session = sessionFactory.openSession();
        }
        Transaction transaction = null;

        transaction = session.beginTransaction();

        T occupiedBedsEntity = (T) session.load(classToRead, Integer.parseInt(id.toString()));
        transaction.commit();

        return occupiedBedsEntity;
    }

    public void update(T o) {
        Session session;
        try {
            session = sessionFactory.getCurrentSession();
        } catch (HibernateException ex) {
            session = sessionFactory.openSession();
        }
        Transaction transaction = null;

        transaction = session.beginTransaction();

        session.update(o);

        transaction.commit();
    }

    public abstract void delete(ID id);

    public abstract List list();
}

AnalysisDao

public class AnalysisDao extends CrudDao<Integer, AnalysisEntity>{


    public AnalysisDao( SessionFactory sessionFactory){
        super(sessionFactory);
    }

    public void delete(Integer id) {
        Session session;
        try {
            session = sessionFactory.getCurrentSession();
        } catch (HibernateException ex) {
            session = sessionFactory.openSession();
        }
        Transaction transaction = null;

        transaction= session.beginTransaction();
           SQLQuery query = session.createSQLQuery("DELETE FROM analysis WHERE id = :analys_id");
            query.addEntity(AnalysisEntity.class);
            query.setParameter("analys_id",id);
            query.executeUpdate();

        transaction.commit();
    }

    public List list(){
        Session session;
        try {
            session = sessionFactory.getCurrentSession();
        } catch (HibernateException ex) {
            session = sessionFactory.openSession();
        }
        Transaction transaction = null;

        transaction= session.beginTransaction();

        List staffEntity =  session.createQuery("FROM AnalysisEntity").list();
        transaction.commit();

        return staffEntity;
    }
}

PatienceDao (almost the same as AnalysisDao)
Mapping xml files look like this:
AnalysisEntity.hbm.xml

<hibernate-mapping default-cascade="all" default-lazy="false">

    <class name="entity.AnalysisEntity" table="analysis" schema="" catalog="medicine">
        <id name="id">
            <column name="id" sql-type="int unsigned" not-null="true"/>
            <generator class="native"/>
        </id>
        <many-to-one name="typeOfAnalys" column="id_type_of_analysis" class="entity.TypeOfAnalysisEntity" />
        <many-to-one name="patience" column="id_patience" class="entity.PatienceEntity"/>
    </class>
</hibernate-mapping>

PatienceEntity.hbm.xml

<hibernate-mapping default-cascade="all" default-lazy="false">

    <class name="entity.PatienceEntity" table="patience" schema="" catalog="medicine">
        <id name="id">
            <column name="id" sql-type="int unsigned" not-null="true"/>
        </id>
        <property name="fio">
            <column name="FIO" sql-type="varchar" length="100" not-null="true"/>
        </property>
        <set name="analysis">
            <key column="id_patience"></key>
            <one-to-many   class="entity.AnalysisEntity"/>
        </set>
        <set name="disease" table="patiente_in_hospital">
            <key column="id_patience"></key>
            <many-to-many column="id_disease" class="entity.DiseaseEntity"/>
        </set>
    </class>
</hibernate-mapping>

The error is on these lines

AnalysisEntity analysisEntity = AnalysisEntity.class.cast(entity);
                TypeOfAnalysisDao typeOfAnalysisDao = new TypeOfAnalysisDao(Main.getOurSessionFactory());

                TypeOfAnalysisEntity typeOfAnalysisEntity =  typeOfAnalysisDao.read(Integer.parseInt(firstField.getText()), TypeOfAnalysisEntity.class);
                analysisEntity.setTypeOfAnalys(typeOfAnalysisEntity);

                PatienceDao patienceDao  =new PatienceDao(Main.getOurSessionFactory());
                analysisEntity.setPatience(patienceDao.read(Integer.valueOf(lastField.getText()), PatienceEntity.class));

error stack

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException:
Caused by: org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions. Collection : [entity.PatienceEntity.analysis#1]
  at org.hibernate.collection.internal.AbstractPersistentCollection.setCurrentSession(AbstractPersistentCollection.java:623)
  at org.hibernate.event.internal.OnUpdateVisitor.processCollection(OnUpdateVisitor.java:46)
  at org.hibernate.event.internal.AbstractVisitor.processValue(AbstractVisitor.java:104)
  at org.hibernate.event.internal.AbstractVisitor.processValue(AbstractVisitor.java:65)
  at org.hibernate.event.internal.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:59)
  at org.hibernate.event.internal.AbstractVisitor.process(AbstractVisitor.java:126)
  at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performUpdate(DefaultSaveOrUpdateEventListener.java:293)
  at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsDetached(DefaultSaveOrUpdateEventListener.java:227)
  at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:92)
  at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:73)
  at org.hibernate.internal.SessionImpl.fireSaveOrUpdate(SessionImpl.java:647)
  at org.hibernate.internal.SessionImpl.saveOrUpdate(SessionImpl.java:639)
  at org.hibernate.engine.spi.CascadingActions$5.cascade(CascadingActions.java:218)
  at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:379)
  at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:304)
  at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:146)
  at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:95)
  at org.hibernate.event.internal.AbstractSaveEventListener.cascadeBeforeSave(AbstractSaveEventListener.java:425)
  at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:249)
  at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:178)
  at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:109)
  at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:192)
  at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:38)
  at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:177)
  at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:32)
  at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:73)
  at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:678)
  at org.hibernate.internal.SessionImpl.save(SessionImpl.java:670)
  at org.hibernate.internal.SessionImpl.save(SessionImpl.java:665)
  at dao.CrudDao.create(CrudDao.java:36)
  at FX.StaffController.handleNewStaff(StaffController.java:204)
  ... 62 more

Actually a question: where the second session opens? Could it be from class cross references to each other?

Answer 1

It appears from your code - if you cannot get the current session with sessionFactory.getCurrentSession, then you create it, but do not close it.
To get the current session, you need to set up some implementation of CurrentSessionContext , such as ThreadLocalSessionContext .

IMHO

• Нет смысла использовать транзакции при чтении
  
• Используй аннотации вместо XML, будет значительно проще