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Hibernate session successfully update object, but occasionally not

I working with PostgreSQL in multithread mode by Hibernate sessions. Init:
<property name="connection.driver_class">org.postgresql.Driver</property>
<property name="hibernate.current_session_context_class">thread</property>
(other strings is connection URL and entity xml describe))
HibernateUtil:
public class HibernateUtil {
private static SessionFactory sessionFactory;
static {
try {
Configuration configuration = new Configuration();
configuration.configure();
sessionFactory = configuration.buildSessionFactory();
} catch (Throwable ex) {
throw new ExceptionInInitializerError(ex);
}
}
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
public static Session getSession() {
return sessionFactory.getCurrentSession();
}
public static void close() {
sessionFactory.close();
}
public static void setSessionFactory(SessionFactory factory) {
sessionFactory = factory;
}
}
All CRUD actions with Entities i do in separate class, where every action execute in one transaction.
public class SessionService {
public static <T> T get(Class<T> classvar, int id) {
Session session = HibernateUtil.getSession();
session.beginTransaction();
T result = session.get(classvar, id);
session.getTransaction().commit();
return result;
}
// Some other code
public static void update(Object obj) {
Session session = HibernateUtil.getSession();
session.beginTransaction();
session.update(obj);
session.getTransaction().commit();
}
}
There is no problems with multithreading work (or i not see it). But, some time ago i seen strange bug. I got one record from db by SessionService.get(Entity.class, 1). Change one field of this entity and save it by SessionService.update(entity). Update was successfull done without exceptions (logging approved). But changes not seen in database. In runtime entity has this changes, but not in db. I wait some time (for flush and others) but nothing changed.
Tried to repeat bug - all good, bug not found. In one day i catch this bug on production server with 19 objects from 200, but in other days i not seen this bug.
Last importan moment: i dont catched this bug with other entities (or i dont see them).
What may be reason of it? May be better use entity manager instead sessions?

Can you please post the entire hibernate.cfg.xml file (delete the username and password of course).
Also are you 100% sure that you do not get an error like (wild guess) :
A different object with the same identifier value was already associated with the session ?
There are errors while running Hibernate, that literary flashes in the console for half a second when running queries.
Had this problem a while back.

How to handle Hibernate connections

I'm new to Hibernate. I've created the SessionFactory and obtaining the Session like below. And I'm using c3p0 connection provider
public static SessionFactory getSessionFactory() {
try {
if (sessionFactory == null) {
Configuration configuration = loadDBConfiguration();
if (configuration != null) {
sessionFactory = configuration.buildSessionFactory();
} else {
log.info("---- Configuration failed ----");
}
}
} catch (Exception ex) {
log.info("---- Initial SessionFactory creation failed ----");
}
return sessionFactory;
}
public static EntityManagerFactory getEntityManagerFactory() {
try {
Session session = getSessionFactory().openSession();
entityManagerFactory = session.getEntityManagerFactory();
} catch (Exception e) {
log.error(e);
}
return entityManagerFactory;
}
public static EntityManager getEntityManager() {
try {
EntityManagerFactory entityManagerFactory = getEntityManagerFactory();
return entityManagerFactory.createEntityManager();
} catch (Exception e) {
log.error(e);
}
return null;
}
And i'm confused with below things.
Should i close the connection after commit(), or c3p0 connection provider will close after commit().
Shall i call getEntityManager() on each request or should i use like singleton
If i'm used as singleton, then does it affect any parallel transaction.begin() or transaction.commit() if server receives multiple request at same time.
Also in singleton the entity still persist in session until it gets closed or clear manually. So what i need to do in this case.
Currently the getEntityManager() gets called in all my EntityManager Classes like UserManager, AccountsManager. After some period of time in RDS it shows like 20connections, even my application not handling any user requests.

You should close your connections. Since your connections are wrapped by the database connection pool, they will not get physically closed, but they will return to the pool. This needs to be done otherwise the connection pool will think the connections are being used and when you hit the pool limit, no new connections will be open.
Keep the session factory as a singleton. You should open a new session for each thread.

Hibernate and multiThread Logic

Im working on a java standAlone project. I need to use hibernate in a MultiThread application but i just cant figure it out how to set up this correctly.
Each Thread deals with the same process of the others.
Everything goes Ok when i run it in a Non-Async way, but when i call the same thing using threads, hibernate just don't work fine.
Can anyone please explain me what's the correct way to use Hibernate in a multiThread Java Stand-Alone App?
Hibernate Util
public class HibernateUtil {
private static final Session session;
static {
try {
SessionFactory sessionFactory;
Properties properties = new Properties();
properties.load(new FileInputStream("middleware.properties"));
Configuration cfg = new Configuration().configure();
cfg.addProperties(properties);
ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
.applySettings(cfg.getProperties()).build();
sessionFactory = cfg.buildSessionFactory(serviceRegistry);
session = sessionFactory.openSession();
} catch (IOException | HibernateException he) {
JOptionPane.showMessageDialog(null, DataBaseMessage.CONNECTION_ERROR.getMessage(), DataBaseMessage.CONNECTION_ERROR.getTitle(),JOptionPane.ERROR_MESSAGE);
throw new ExceptionInInitializerError(he);
}
}
public static Session getSession() {
return session;
}
The Error comes here
TbHistoDespachos despacho = Dao.findDespachoByTagId(element.getChild("tagID").getText());
public synchronized List<TbHistoDespachos> ExractDespachoAndNotify(String data, String nombreConexion) {
List<TbHistoDespachos> despachos = new ArrayList<>();
String nombreConexionUpp = nombreConexion.toUpperCase();
try {
Document doc = convertStringToDocument(data);
if (!doc.getRootElement().getChild("reply").getChild("readTagIDs")
.getChildren().isEmpty()) {
for (Element element : doc.getRootElement().getChild("reply").
getChild("readTagIDs").getChild("returnValue")
.getChildren()) {
TbHistoDespachos despacho = Dao.findDespachoByTagId(element.getChild("tagID").getText());
if (despacho != null) {
if(evaluateDespacho(nombreConexionUpp, despacho)){
despachos.add(despacho);
}
}
}
}
} catch (JDOMException | IOException ex) {
JOptionPane.showMessageDialog(null, FilesMessageWarnings.NOTIFICATION_SAP_WARNING.
getMessage().replace("&nombreConexion", nombreConexion).replace("&tagID", ""),
FilesMessageWarnings.NOTIFICATION_SAP_WARNING.getTitle(), JOptionPane.WARNING_MESSAGE);
}
return despachos;
}
Here is the DAO
public class Dao {
private static Session sesion;
public static TbHistoDespachos findDespachoByTagId(String tagId) {
TbHistoDespachos despacho = null;
try {
startTransmission();
despacho = (TbHistoDespachos)sesion.createQuery("FROM TbHistoDespachos WHERE TAG_ID =:tagId")
.setParameter("tagId", tagId)
.uniqueResult();
stopTransmission();
} catch (HibernateException he) {
System.out.println("error: " + he.getMessage());
JOptionPane.showMessageDialog(null, DataBaseMessage.QUERY_ERROR.getMessage(),
DataBaseMessage.QUERY_ERROR.getTitle(), JOptionPane.ERROR_MESSAGE);
}
return despacho;
}
private static void startTransmission() {
sesion = HibernateUtil.getSession();
sesion.getTransaction().begin();
}
private static void stopTransmission() {
sesion.getTransaction().commit();
sesion.getSessionFactory().getCurrentSession().close();
sesion.clear();
}
ANY IDEAS?

The problem stems from static Session variables. A SessionFactory is thread-safe and, generally speaking, you only need one (static) instance per database. A Session, on the other hand, is not thread-safe and is usually created (using a SessionFactory) and discarted/closed on the fly.
To solve your immediate problem, remove the static Session sesion variable from your Dao and also 'inline' the startTransmission and stopTransmission methods in the findDespachoByTagId method. This will ensure that each thread calling findDespachoByTagId creates and uses its own session instance. To analyze the current problem, imagine two threads calling findDespachoByTagId at the same time. Now the static session variable will be assigned a value twice by the startTransmission method. This means one session instance is lost almost immediatly after it was created while the other one is used by two threads at the same time. Not a good thing.
But there are other problems too: there are no finally blocks that guarantee transactions are closed and database connections are released (via the closing of sessions). Also, you will probably want to use a database pool as the one provided by Hibernate is not suitable for production. I recommend you have a look at HibHik: I created this project to show a minimal stand-alone Java application using Hibernate with a database pool (HikariCP) that uses the recommended patterns and practices (mostly shown in TestDbCrud.java). Use the relevant parts in your application, than write multi-threaded unit-tests to verify your database layer (DAO) is working properly, even in the case of failure (e.g. when the database is suddenly no longer available because the network-cable was unplugged).

Hibernate + Jersey + Jackson getting “org.hibernate.TransactionException: nested transactions not supported” randomly

I have buit a Webservice using these technologies + c3p0 for database handling. It works ok most of the time but I have a 3-5% ratio (sometimes even a 10%) of failed acces due to this error.
I am using Hibernate this way:
-Session Factory
private static SessionFactory buildSessionFactory() {
try {
Configuration configuration = new Configuration();
configuration.configure();
serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
// Create the SessionFactory from hibernate.cfg.xml
return configuration
.buildSessionFactory(serviceRegistry);
} catch (Throwable ex) {
System.err.println("Initial SessionFactory creation failed." + ex);
throw new ExceptionInInitializerError(ex);
}
}
public static SessionFactory getSessionFactory() {
//reabrimos la sesion si esta cerrada al liberar los recursos
if(sessionFactory.isClosed())
{
System.out.println("Reopen session");
sessionFactory.openSession();
}
return sessionFactory;
}
Then in my hibernate.cfg.xml I have the following line:
<property name="current_session_context_class">thread</property>
Finally in my endpoints I have defined a hibernate_session class which I use as follows:
#Path("/projects")
public class ProjectServiceImpl {
#Context
SecurityContext security;
Session hibernate_session = null;
#POST
#Path("sync.json")
#Produces(value = {"application/json",
"application/vnd.myapp-v1+json",
"application/vnd.myapp-v2+json"})
public Response syncProjects(
#DefaultValue("") #FormParam("projects") String in_projects_str,
#DefaultValue("0") #FormParam("last_sync") long last_sync,
#Context Request request) {
//...
hibernate_session = HibernateUtil.getSessionFactory()
.getCurrentSession();
if (hibernate_session == null) {
ResponseMessage rm = new ResponseMessage();
rm.setCode(Status.INTERNAL_SERVER_ERROR.getStatusCode());
rm.setMessage("Hibernate Session is Null");
rm.setType("ERROR");
return Response.status(Status.INTERNAL_SERVER_ERROR).entity(rm)
.type("application/json").build();
}
try {
hibernate_session.beginTransaction();
//Database work...
hibernate_session.flush();
hibernate_session.getTransaction().commit();
}catch (RuntimeException | IllegalAccessException
| InvocationTargetException e) {
try {
if (hibernate_session.getTransaction() != null) {
hibernate_session.getTransaction().rollback();
}
} catch (RuntimeException rbe) {
System.err.println("Couldn’t roll back transaction");
}
e.printStackTrace();
ResponseMessage rm = new ResponseMessage();
rm.setCode(Status.INTERNAL_SERVER_ERROR.getStatusCode());
rm.setMessage(e.getMessage());
rm.setType("ERROR");
return Response.status(Status.INTERNAL_SERVER_ERROR).entity(rm)
.type("application/json").build();
}
}
return Response.ok().entity(result_entity)
.type("application/json").build();
}
My hibernate_session is a class attribute, do I have to change it to a local variable?. As far as I know the end points will be executed in different threads so I have assumed that I am working with different instances of my endpoint container class and these class attributes will not get overriden by multiple request.
Any light you can shed on this topic will be appreciated,
Thanks in advance

Thanks all for your replies. I finally managed to solve the problem.
In one of my multiple entries there was a begin transaction (necessary to create criterias) but was not commited. The result was that a reused thread that had called that method before would throw a nested exception. By commiting the transaction the problem was solved :)

You aren't using openSession and getCurrentSession properly.
public static SessionFactory getSessionFactory() {
//reabrimos la sesion si esta cerrada al liberar los recursos
//change this: if(sessionFactory.isClosed()) to this:
if(sessionFactory == null || sessionFactory.isClosed())
{
System.out.println("Reopen session"); // Really setup session factory
//change this: sessionFactory.openSession(); to this:
sessionFactory = buildSessionFactory();
}
return sessionFactory;
}
That's not the problem though, your code there just isn't doing what it's supposed to. You need to change:
hibernate_session = HibernateUtil.getSessionFactory().getCurrentSession();
to
hibernate_session = HibernateUtil.getSessionFactory().openSession();
As per the SessionFactory Javadoc:
Obtains the current session. The definition of what exactly "current" means controlled by the CurrentSessionContext impl configured for use.
It's safe to assume your CurrentSessionContext is not thread safe.

It seems that a transaction is started, and before the transaction gets commited an attempt to start a new transaction is made.
This explains the error message that says that a nested transaction (the second transaction inside the ongoing transaction) is not supported.
This could be caused for example by incorrect error handling, for example starting a transaction, not catching an exception or catch and ignore and then try to begin a second transaction without having done either commit or rollback.
An idiom similar to this one should be used when doing programmatic transaction mananagement:
try {
sess.getTransaction().begin();
// do some work
sess.getTransaction().commit()
}
catch (RuntimeException e) {
sess.getTransaction().rollback();
throw e;
}
Also important to bear mind is that after a rollback the session cannot be reused, as it's in an inconsistent state.
If using a framework like Spring, the use of the annotation #Transactional for declarative transaction management solves most of these problems for us and leads to more maintainable code, EJB3 has also similar functionality.

Hibernate Sessionfactory restart | Spring

My requirement is as follows:
I need to restart(or rebuild) hibernate session factory in my Spring web application at frequent intervals with the new HBM files I get from outside.
Currently my Sessionfactory class is as follows with a SessionFactory Proxy to intercept 'OpenSession' call.
There I am checking for a condition to restart and rebuilding sessionFactory.
My problem here is , in concurrent environment the other users who are in middle of other transaction is getting affected during this restart.
Is there anyway to carryout the restart by checking all the transactions and open sessions and carry out rebuilding session factory once all other completes?
or any other solution exists.
Code:
public class DataStoreSessionFactory extends LocalSessionFactoryBean
{
private boolean restartFactory = false;
#Override
protected void postProcessConfiguration(Configuration config) throws HibernateException
{
super.postProcessConfiguration(config);
updateHBMList(config);
}
private void updateHBMList(final Configuration config)
{
config.addXML(modelRegistry.generateMapping());
}
#Override
public SessionFactory getObject()
{
Object obj = super.getObject();
/*
* Invocation handler for the proxy
*/
SessionFactoryProxy proxy = new SessionFactoryProxy(this, (SessionFactory) obj);
/**
* All the methods invoked on the returned session factory object will pass through this proxy's invocation
* handler
*/
SessionFactory sessionFactory = (SessionFactory) Proxy.newProxyInstance(getClass().getClassLoader(),
new Class[] { SessionFactory.class },
proxy);
return sessionFactory;
}
static class SessionFactoryProxy implements InvocationHandler
{
private SessionFactory sessionFactory;
private LocalSessionFactoryBean factoryBean;
public SessionFactoryProxy(LocalSessionFactoryBean factoryBean, SessionFactory sessionFactory)
{
this.factoryBean = factoryBean;
this.sessionFactory = sessionFactory;
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
{
/**
* Only if the method invoked is openSession - check if the session factory should be restarted, and only then
* invoke the requested method
*/
if (method.getName().equals("openSession"))
{
restartSessionFactoryIfNecessary();
}
return method.invoke(sessionFactory, args);
}
private void restartSessionFactoryIfNecessary()
{
restartSessionFactory();
/*if (((DataStoreSessionFactory) factoryBean).isRestartFactory())
{
restartSessionFactory();
}*/
}
private synchronized void restartSessionFactory()
{
log.info("Restarting session...");
factoryBean.destroy();
try
{
factoryBean.afterPropertiesSet();
sessionFactory = factoryBean.getObject();
}
catch (Exception e)
{
log.error("Error while restarting session: " + e.getMessage());
throw new RuntimeException(e);
}
}
}
Thanks,
Appasamy

You can following SessionFactoryUtils to determine whether a transaction is taking place in Session factory and then decide to restart the session factory or not:
You will need to import--> org.springframework.orm.hibernate.SessionFactoryUtils in you file, and use the following API.
static boolean hasTransactionalSession(SessionFactory sessionFactory);
Above API returns whether there is a transactional Hibernate Session for the current thread, that is, a Session bound to the current thread by Spring's transaction facilities.There is also another API just in case if you need to check if a session is transactional in session factory currently:
static boolean isSessionTransactional(Session session,SessionFactory sessionFactory);
Above API returns whether the given particular Hibernate Session is transactional, that is, bound to the current thread by Spring's transaction facilities.