休眠 session.save() 不反映在数据库中

Question

According to my understanding in hibernate (please confirm)

1- You have to session.close() if you get it by getSessionFactory().openSession() .
2- No need to session.close() if you get it by getSessionFactory().getCurrentSession() . It is automatically closed after commit() .

3- @2 When using getSessionFactory().getCurrentSession() , we have to do all DB activities inside an active transaction so that we can commit() at the end.

4- Hibernate en-queues all save, update, and delete operations and submits them to the database server only after a flush() operation or committing the transaction or closing of the session in which these operations occur.(as per javadoc)

From the above points if I consider 1 & 4 , then the following code should work:

Session session = HibernateUtil.getSessionFactory().openSession();  
AccountDetails ac = new AccountDetails();  
//perform set operations  
session.save(ac);  
session.close();  
System.out.println("new account stored.");

BUT it is not working ie it runs smoothly but does not reflect(store) in database.Why this is so ? When I write the code inside a transaction and commit, then it is stored.

I think I am missing a basic thing. Please clarify.

Answer 1

When you create session using SessionFactory.openSession(), no transaction is created, so your operations are executed outside of transaction context. In order to see your changes, you have to start a new transaction, or perform your operations as a part of ongoing transaction. From documentation:

A typical transaction should use the following idiom:

Session sess = factory.openSession();
 Transaction tx;
 try {
     tx = sess.beginTransaction();
     //do some work
     ...
     tx.commit();
 }
 catch (Exception e) {
     if (tx!=null) tx.rollback();
     throw e;
 }
 finally {
     sess.close();
 }

Answer 2

I was also trying to understand the point: save() can perform Insert operation outside transaction boundary so I did something like this

SessionFactory factory = new Configuration().configure()
                    .buildSessionFactory();
            Session session = factory.openSession();

            session.save(user);

            session.close();

But data not inserted in database.So I again tried this and now it worked for me and data inserted sucessfully:

in configuration file:

  <property name="connection.autocommit">true</property>

and in java code:

    SessionFactory factory = new Configuration().configure()
            .buildSessionFactory();
    Session session = factory.openSession();

    session.save(user);

    session.flush();
    session.close();

Answer 3

Yeah session.save is not saved to database without have the transaction. Only way to do it is by using the

<property name="connection.autocommit">true</property>

If this property is used you no need transaction and also you do not need session.flush() or session.close()

Answer 4

session.close() is only responsible to close the session https://docs.jboss.org/hibernate/orm/3.5/javadocs/org/hibernate/Session.html#close()

how to work with hibernate session: https://docs.jboss.org/hibernate/orm/3.3/reference/en/html/transactions.html#transactions-basics

// Non-managed environment idiom
Session sess = factory.openSession();
Transaction tx = null;
try {
    tx = sess.beginTransaction();

    // do some work
    ...

    tx.commit();
}

catch (RuntimeException e) {
    if (tx != null) tx.rollback();
    throw e; // or display error message
}
finally {
    sess.close();
}

As it wrote in the documentation: a much more flexible solution is Hibernate's built-in "current session" context management:

// Non-managed environment idiom with getCurrentSession()
try {
    factory.getCurrentSession().beginTransaction();

    // do some work
    ...

    factory.getCurrentSession().getTransaction().commit();
}
catch (RuntimeException e) {
    factory.getCurrentSession().getTransaction().rollback();
    throw e; // or display error message
}

Answer 5

Whenever you carry out any unit of work on the database objects, Transactions have to be used. http://docs.jboss.org/hibernate/orm/4.0/hem/en-US/html/transactions.html shows why they are used and how they can be used. But, the key is to use a transaction object by calling session.beginTransaction() which returns a Transaction object. This will represent the unit of work carried out to the database.

Answer 6

I found I had to flush and then refresh the DAO, and then it worked.

session.flush()
session.refresh(entityDAO)

Answer 7

You forgot to commit .You should to commit.

session.save(ac);
// you should to add this bottom line  
session.getTransaction().commit();

Answer 8

Whenever Your are doing save(), Always commit the transaction once done.

Account ac =new account()
ac.insert(123);
----------
----------
----------
----------
session.save(ac);

// Add this bottom line  
session.getTransaction().commit();

Answer 9

if there is DB manipulation operation then it should be in transaction
if you call session.save(object)
hibernate create bellow query only .
select hibernate_sequence.nextval from dual
so right code is here
Transaction  t=session.beginTransaction();
session.save(obect);
t.commit(); should not forgot to commit.
session.close();