I have the following save method which inserts and commits the object into my database:
public void save() {
Session session = HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
session.save(this);
session.getTransaction().commit();
}
However, if I use the decorator, it never actually commits to the database:
#Transactional
public void save() {
Session session = HibernateUtil.getSessionFactory().openSession();
session.save(this);
}
Is there something additional I need to do in order for connection to commit it?
The #Transactional annotation will already create a transaction using a proxy.
So you don't need to open a new session from your sessionFactory, you just need to get the current one.
This should work for you:
Session session = HibernateUtil.getSessionFactory().getCurrenstSession();
session.save(this);
Please let me know if it worked :)
Related
This question already has answers here:
Hibernate openSession() vs getCurrentSession()
(5 answers)
Closed 4 years ago.
If I use getCurrentSession() to obtain session and I don't begin transaction and save gives exception but when I use openSession() to get session then in the same scenario the program runs without any exception."hibernate.current_session_context_class" is configured with thread in hibernate configuration file.So what is the difference when I use getCurrentSession() and openSession().
Here is the code that gets session using getCurrentSession()-
public static void main(String ar[])
{
SessionFactory sfac=null;
sfac=new Configuration().configure("hibernateconfig/rs.xml")
.buildSessionFactory();
try {
Session session=sfac.getCurrentSession();
Student stu=new Student();
stu.setFirstName("abc23");
stu.setLastName("xyz");
System.out.println("-------------"+stu);
session.save(stu);
}
catch(Exception e)
{
System.out.println(e);
}
}
output-
-------------Student [id=0, firstName=abc23, lastName=xyz]
org.hibernate.HibernateException: save is not valid without active transaction
Here is the code that gets session using openSession()-
public static void main(String ar[])
{
SessionFactory sfac=null;
sfac=new Configuration().configure("hibernateconfig/rs.xml")
.buildSessionFactory();
try {
Session session=sfac.openSession();
Student stu=new Student();
stu.setFirstName("abc23");
stu.setLastName("xyz");
System.out.println("-------------"+stu);
session.save(stu);
}
catch(Exception e)
{
System.out.println(e);
}
}
output-
-------------Student [id=0, firstName=abc23, lastName=xyz]
Hibernate:
insert
into
student
(firstName, lastName)
values
(?, ?)
openSession():
When you call SessionFactory.openSession(), it always create new Session object and give it to you.You need to explicitly flush and close these session objects. As session objects are not thread safe, you need to create one session object per request in multithreaded environment and one session per request in web applications too.
getCurrentSession():
When you call SessionFactory. getCurrentSession(), it will provide you session object which is in hibernate context and managed by hibernate internally. It is bound to transaction scope.When you call SessionFactory.getCurrentSession() , it creates a new Session if not exists , else use same session which is in current hibernate context. It automatically flush and close session when transaction ends, so you do not need to do externally.If you are using hibernate in single threaded environment , you can use getCurrentSession(), as it is faster in performance as compare to creating new session each time.You need to add following property to hibernate.cfg.xml to use getCurrentSession method.
thread
if I use SessionFactory
private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
public Session getSession() {
return sessionFactory.openSession();
}
And use it in my DAO class:
public List<Entity> fetchEntities(Date fromDate, Date toDate) {
Criteria criteria = getSession().createCriteria(Entity.class);
criteria.add(Restrictions.between("cts", fromDate, toDate));
criteria.addOrder(Order.desc("cts"));
return (List<Entity>) criteria.list();
}
Need I close session or not? How curectly do it?
public List<Entity> fetchEntities(Date fromDate, Date toDate) {
Criteria criteria = getSession().createCriteria(Entity.class);
criteria.add(Restrictions.between("cts", fromDate, toDate));
criteria.addOrder(Order.desc("cts"));
return (List<Entity>) criteria.list();
}
Need I close session or not? How correctly do it?
If you create a session instance and close it for each executed query, it may work but it may also have side effects such as a connection pool bottleneck or a overuse of memory.
close() releases the JDBC connection and performs some cleaning.
The Connection close() method of the org.hibernate.Interface Session class states :
End the session by releasing the JDBC connection and cleaning up.
So you should not open and close the session for each executed query.
You should rather close the connection when all queries associated to a client request/processing (user, batch ...) were executed.
Of course if the client request consists of a single query, it makes sense to close it after the query execution.
Actually you use SessionFactory.openSession() that creates a new session that is not bound to the Hibernate persistence context.
It means that you have to explicitly close the session as you finish working with it otherwise it will never be closed.
Supposing that the method is the single one executed in the client request, you could write something like :
public List<Entity> fetchEntities(Date fromDate, Date toDate) {
Session session;
try{
session = getSession();
Criteria criteria = session.createCriteria(Entity.class);
criteria.add(Restrictions.between("cts", fromDate, toDate));
criteria.addOrder(Order.desc("cts"));
return (List<Entity>) criteria.list();
}
finally {
if (session != null) {
session.close();
}
}
Note that if you used SessionFactory.getCurrentSession(), you would not need to close it explicitly as it obtains the current session from the persistence context that creates the session as the transaction is started and close it as the transaction is finished.
The scope of the hibernate session should be the current unit of work (i.e. the transaction) (keep it mind that session is not thread safe).
The factory should be kept for the whole app lifecycle.
See also Struggling to understand EntityManager proper use
No. Actually your web franework ( like spring ) or declarative transaction anagement will do this for you. But there are some cases when you would like to manage sessions yourself. Like batch processing - as hibernate session caches are growing constantly
Do we have to close the session after its usage? As I understood SessionFactory closes sessions if it needed. For example:
#Autowired
private SessionFactory sessionFactory;
public long count(String extId) {
Session session = this.sessionFactory.getCurrentSession();
BigDecimal count = (BigDecimal) session
.createSQLQuery(
"SELECT COUNT(*) FROM smsc.queue WHERE extId=:extId AND nextId IS NULL")
.setString("extId", extId).uniqueResult();
return count.longValue();
}
This is my DAO method called in my services. Does that mean I have to close session every time?
Yes. When you are finished with it you should close it. You need not explicitly close it yourself, there are frameworks that can do this for you.
It is not an expensive operation to open and close sessions. It is usually problematic keeping them open too long as your cached session data grows more stale over time.
A Session is opened when getCurrentSession() is called for the first time and closed when the transaction ends. It is also flushed automatically before the transaction commits.
https://developer.jboss.org/wiki/OpenSessionInView
Use this general formula to close connection in your code
try {
connection = dataSource.getConnection();
// Do stuff with connection.
} finally {
connection.close();
}
Check more here
Can you have multiple transactions within one Hibernate Session?
I'm unclear if this is an allowable desirable. In my code I have a long running thread and takes items from a Blocking Queue, depending on what is on the queue, it may need to create and save a hibernate object, or it may not need to do anything.
Each item is distinct so if item 1 is saved and item 2 fails to save whatever reason I don't want to that to prevent item 1 being added to the database.
So the simplest way to do this is for each item that needs to be created to create a new session, open transaction, save new object, commit transaction, close session
However, that means a new session is created for each item, which seems to go against Hibernates own recommendations to not do Session Per Request Pattern. So my alternative was to create one session in the thread, then just open and commit a new transaction as required when needed to create a new object. But I've seen no examples of this approach and I'm unsure if it actually works.
The session-per-request pattern uses one JDBC connection per session if you run local transactions. For JTA, the connections are aggressively released after each statement only to be reacquired for the next statement.
The Hibernate transaction API delegates the begin/commit/rollback to the JDBC Connection for local transactions and to the associated UserTransaction for JTA. Therefore, you can run multiple transactions on the same Hibernate Session, but there's a catch. Once an exception is thrown you can no longer reuse that Session.
My advice is to divide-and-conquer. Just split all items, construct a Command object for each of those and send them to an ExecutorService#invokeAll. Use the returned List to iterate and call Future#get() to make sure the original thread waits after all batch jobs to complete.
The ExecutorService will make sure you run all Commands concurrently and each Command should use a Service that uses its own #Transaction. Because transactions are thread-bound you will have all batch jobs run in isolation.
Obviously, you can. A hibernate session is more or less a database connection and a cache for database objects. And you can have multiple successive transactions in a single database connection. More, when you use a connection pool, the connection is not closed but is recycled.
Whether you should or not is a matter of reusing objects from session. If there is a good chance but you can reuse objects that a preceding transaction has put in session, you should keep one single session for multiple transactions. But if once an object has been committed, it will never be re-used, it is certainly better to close the session and re-open a new one, or simply clear it.
How to do it :
If you have a Session object, you create transactions with :
Transaction transaction;
transaction = session.beginTransaction();
... (operations in the context of transaction)
transaction.commit();
... (other commands outside of any transaction)
transaction = session.beginTransaction();
... (and so on and so forth ...)
From hibernates documentation
"A Session is an inexpensive, non-threadsafe object that should be used once and then discarded for: a single request, a conversation or a single unit of work. A Session will not obtain a JDBC Connection, or a Datasource, unless it is needed. It will not consume any resources until used."
so if you are creating sessions again and again it will not burden the system much. If you are continuing a session for too long it may create problems as session is not thread safe .In my opinion you simplest solution is the best "So the simplest way to do this is for each item that needs to be created to create a new session, open transaction, save new object, commit transaction, close session"
By the way if you are creating single record of anything you dont need transaction too much. creating single record is inherently " all or none" thing for which we use transaction
package hibernate;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
class Tester {
public static void main(String[] args) {
SessionFactory sf = new org.hibernate.cfg.Configuration().configure().buildSessionFactory(new StandardServiceRegistryBuilder().configure().build());
Session session = sf.openSession();
session.beginTransaction();
Student student = new Student();
student.setName("Mr X");
student.setRollNo(13090);
session.save(student);
session.getTransaction().commit();
session.getTransaction().begin();
session.load(Student.class,23);
student.setName("New Name");
student.setRollNo(123);
session.update(student);
session.getTransaction().commit();
session.close();
}
}
Short answer is yes, you can use same session for transaction. Take a look at org.hibernate.Transaction., it has required method to manage transaction.
docs.jboss.org Chapter 13. Transactions and Concurrency
Use a single database transaction to serve the clients request, starting and committing it when you open and close the Session. The relationship between the two is one-to-one and this model is a perfect fit for many applications.
It seemed we should always obey the "one-to-one relationship" rule.
But, although the sample below will trigger a exception in the line where the second "session.beginTransaction()" is called
Exception in thread "main" java.lang.IllegalStateException: Session/EntityManager is closed
private static void saveEmployees(SessionFactory factory) {
// crate session
//Session session = factory.openSession();
Session session = factory.getCurrentSession();
{
// start a transaction
Transaction trans = session.beginTransaction();
// create an employee
Employee tempEmployee = new Employee("Steve","Rogers", "The Avengers");
// save to database
session.save(tempEmployee);
// commit the transaction
trans.commit();
}
{
// start a transaction
Transaction trans = session.beginTransaction();
// create an employee
Employee tempEmployee = new Employee("Tony","Stark", "The Avengers");
// save to database
session.save(tempEmployee);
// commit the transaction
trans.commit();
}
// close session
session.close();
}
, another sample below will work properly.
The only difference is that the second sample uses "factory.openSession()" to get a session, instead of "factory.getCurrentSession()".
private static void saveEmployees(SessionFactory factory) {
// crate session
Session session = factory.openSession();
//Session session = factory.getCurrentSession();
{
// start a transaction
Transaction trans = session.beginTransaction();
// create an employee
Employee tempEmployee = new Employee("Steve","Rogers", "The Avengers");
// save to database
session.save(tempEmployee);
// commit the transaction
trans.commit();
}
{
// start a transaction
Transaction trans = session.beginTransaction();
// create an employee
Employee tempEmployee = new Employee("Tony","Stark", "The Avengers");
// save to database
session.save(tempEmployee);
// commit the transaction
trans.commit();
}
// close session
session.close();
}
I am a starter, and I don't know why "factory.getCurrentSession()" works differently from "factory.openSession()", yet.
I'm still new to JPA and how the entity manager works. I have an application configured with container managed transactions, and I'm trying to figure out how to persist multiple objects in a single transaction. Here is what I tried first:
#Stateless
public class UserManager{
#PersistenceContext(unitname="dataPortal")
EntityManager em;
public void insertUser(User user)
{
em.getTransaction().begin();
ChangeEvent event = new ChangeEvent("user created");
em.persist(u);
em.persist(event);
em.getTransaction().commit();
}
}
This throws an illegal state exception when I try to get the transaction. I found out through reading that you aren't suppose to touch the transaction when it is container managed.
What I want to do is make sure that the User and ChangeEvent objects are persisted in the same transaction. How can I enforce that with container managed transactions?
Like you already said, the transactions are managed by the container.
If you want that both User and ChangeEvent are persisted in the same transaction just annotate your method the following way:
#TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
#TransactionManagement(TransactionManagementType.CONTAINER)
public void insertUser(User user)
{
ChangeEvent event = new ChangeEvent("user created");
em.persist(u);
em.persist(event);
}
This should do the trick. If you have further questions, feel free to ask.