Why hibernate is saving values without transaction?

Question

i'm using spring boot(2.1.4) with hibernate(5.3.9).

public class BaseDao{

@Autowired 
private SessionFactory sessionFactory;

private Session session;
private Transaction transaction;

@Autowired
private EntityManagerFactory entityManagerFactory;

@PersistenceContext
private EntityManager entityManager; 

public SessionFactory getSessionFactory() {
    return sessionFactory;
}

public EntityManagerFactory getEntityManagerFactory() {
    return entityManagerFactory;
}

public EntityManager getEntityManager() {
    return entityManager;
}


public Session getSession() throws Exception{
    if(session == null) {
        session = getSessionFactory().openSession();
    }
    
    if(transaction == null) {
        transaction = session.beginTransaction();
    }
    return session;
}

public void commit() throws Exception{
    if(transaction != null) {
        transaction.commit();
        transaction = null;
    }
    
    if(session != null) {
        session.close();
        session = null;
    }
}

public void rollback() throws Exception{
    if(transaction != null) {
        transaction.rollback();
        transaction = null;
    }

    if(session != null) {
        session.close();
        session = null;
    }
}

protected void save(Object object) throws Exception {
    getSessionFactory().openSession().save(object);    //saves data in db 
    getSession().save(object);    //is not saving data
}   

getSessionFactory().openSession().save(object); this code is saving data to db even without commit getSession().save(object); this code required commit to be called as txn is created but not commited

hibernate log

i see below log for both the line of code

insert into TEST_ENTITY (CREATED_BY, CREATED_DATE, ENABLED, LAST_MODIFIED_BY, LAST_MODIFIED_DATE, NAME) values (?, ?, ?, ?, ?, ?)

i have few questions on this behavior.

1. I know write operation will not happen without commit, so any idea what is wrong here or what causing commit in first scenario ?

2. Is it ok to use above code i.e. first scenario ?

3. If first approach is not right then do i need to create and commit txn for each object, any better approach so that even if i have to commit txn, i don't want to replicate the txn.commit() in every new method i write in BaseDao.java i.e. say i have create(), update(),delete() methods can i move this txn.commit() out of methods ?

4. Few places i'm using spring data jpa for fetching/saving record (given below), how txn is being handled in spring data jpa ? any references ?

   @Repository public interface TestEntitytRepo extends JpaRepository<TestEntity, Long> { ... }

Please let me know if i missed any details to capture here.

Thanks in advance.

Answer 1

In hibernate, the Save() method stores an object into the database. It will Persist the given transient instance, first assigning a generated identifier. It returns the id of the entity created. When a session in hibernate is created using SessionFactory.openSession(), no transaction is created, so all the operations are executed outside of the transaction context !! In order to ensure the data gets saved into the database, a new transaction needs to be created.

I am a bit skeptical about the behaviors explained by you above. Seems like auto-commit option is enabled. If so, then this is not an issue as save() method is done, commit automatically happens backstage !!