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Get number of inserts, updates, deletes for entity using org.hibernate.SessionFactory per Session per thread

I have the following scenario:
I have one controller which based on a path variable calls a different service.
In every service there is a transactional method where some import logic is happening(call one external api, get a csv file, parse it, convert it to entity and save it in database).
Additionally in every service I want to keep statistics of how many entities will be updated, inserted and deleted. For that reason I am using the org.hibernate.SessionFactory . One example of how I am using that is:
#Service
#Slf4j
public class MarketReportImporterImpl extends Support implements MarketReportImporter {
#Override
#Transactional
public void importMarketReports(ImporterLog importerLog) {
try {
String export = getCsvFile();
Session session = getCurrentSessionAndClearSessionFactoryStatistics();
// parse the csv and save the entities
flushSession(session);
setSuccessfulImport(session, importerLog);
} catch (Exception e) {
log.error("Failed to import market reports. Unable to parse export", e);
getTelemetryClient().trackException(e);
importerLogService.setFailedImport(importerLog, e.getMessage());
}
}
and the methods getCurrentSessionAndClearSessionFactoryStatistics() and setSuccessfulImport(session, importerLog); are in the Support class:
#Component
public abstract class Support {
private final ImporterLogService importerLogService;
#PersistenceContext
private EntityManager entityManager;
public Support(ImporterLogService importerLogService) {
this.importerLogService = importerLogService;
}
public void flushSession(Session session) {
session.flush();
}
public void setSuccessfulImport(Session session, ImporterLog importerLog) {
Statistics statistics = session.getSessionFactory().getStatistics();
int entityInsertCount = (int) statistics.getEntityInsertCount();
int entityDeleteCount = (int) statistics.getEntityDeleteCount();
int entityUpdateCount = (int) statistics.getEntityUpdateCount();
importerLogService.setSuccessfulImport(importerLog, entityUpdateCount, entityDeleteCount, entityInsertCount);
}
public Session getCurrentSessionAndClearSessionFactoryStatistics() {
Session session = entityManager.unwrap(Session.class);
SessionFactory sessionFactory = session.getSessionFactory();
sessionFactory.getStatistics().clear();
return session;
}
This works perfectly fine when calling it for one importer. But If from the frontend I am calling quickly two importers (meaning two threads run in parallel) there will be mix in the results. The session.getSessionFactory().getStatistics(); will have mix results from the first importer and from the second importer and I want to have a clear result only for the current session. For example service A and service B are running in parallel and in service A I am saving entities of type aa and in service B of type bb. In each service I want to know how many entities are saved, updated or deleted meaning in service A -> how many of type aa and in service B -> how many of type bb . As I understand every thread should open a session on it's own and then for every session I should get the correct sessionFactory and the correct results. But as it turns out this sessionFactory I guess (not sure in this statement) it belongs to every session and that is why I have mix results.
My question is if there is a way to separate somehow the sessionFactory and have clear vision of which entity how many times is saved,deleted,updated even in multithreaded environment.

If you want the statistics of a session, then call the getStatistics() method on session, which will give you the SessionStatistics. A SessionFactory should only exist once and statistics there are across all sessions.

Dropwizard #UnitOfWork with asynchronous database call

I imagine that this is a common problem, but after some searching I wasn't able to find anything relevant.
The problem I'm having is that I'm getting a No Hibernate Session bound to thread exception when annotating my resource method with #UnitOfWork and inside my resource method, making an asynchronous DAO call. The idea behind this design is to make the database call on a separate I/O thread so that it frees up the Jersey resource thread.
Unfortunately, as the exception says, this RxIoScheduler-2 thread doesn't have a hibernate session bound to it.
Any suggestions?

Hibernate Session is not thread safe, so we need a strategy how to get the current session for the current thread. Such strategy is called CurrentSessionContext.
The current session is a session which we get by this call:
sessionFactory.getCurrentSession()
Hibernate can be configured with various current session strategies. #UnitOfWork uses this strategy:
hibernate.current_session_context_class = managed
For this strategy you should put a session to the context by an explicit call of the
ManagedSessionContext.bind(session)
So, as we know a Session is not thread safe, you should create a new session for a separate thread and put that session in the ManagedSessionContext. After that you can call your DAO by the same way as in the endpoint methods with #UnitOfWork.
Keep in mind that you should unbind the session before closing it with
ManagedSessionContext.unbind(factory)
You can use this utility class to create a session for a separate thread:
public final class HibernateSessionUtils {
private HibernateSessionUtils() {
}
public static void request(SessionFactory factory, Runnable request) {
request(factory, () -> {
request.run();
return null;
});
}
public static <T> T request(SessionFactory factory, Supplier<T> request) {
Transaction txn = null;
Session session = factory.openSession();
try {
ManagedSessionContext.bind(session);
txn = session.beginTransaction();
T result = request.get();
commit(txn);
return result;
} catch (Throwable th) {
rollback(txn);
throw Throwables.propagate(th);
} finally {
session.close();
ManagedSessionContext.unbind(factory);
}
}
private static void rollback(Transaction txn) {
if (txn != null && txn.isActive()) {
txn.rollback();
}
}
private static void commit(Transaction txn) {
if (txn != null && txn.isActive()) {
txn.commit();
}
}
}
Throwables from guava.
It can be used by this way
List<Campaign> getCampaigns(SessionFactory factory, CampaignDao dao) {
return HibernateSessionUtils.request(
factory,
dao::getCampaigns
);
}
In the dao.getCampaigns() method you can get the session
sessionFactory.getCurrentSession()
You can inject the factory everywhere using Guice.
Other option is to use UnitOfWorkAwareProxyFactory.

How to get java.sql.Connection object from Hibernate Session

I have requirement where I need java.sql.Connection. But I am using Hibernate here. Somehow I researched and I found below alternative but that's not working.
import org.hibernate.connection.ProxoolConnectionProvider;
public class ConnectionDB{
//I have imported below class
ProxoolConnectionProvider proxoolProvider = new ProxoolConnectionProvider();
org.hibernate.cfg.Configuration cfg = HibernateUtil.getConfiguration();//this method will return configuration
java.util.Properties props = cfg.getProperties();//This will return Properties Object
//Using properties object I just tried to get The Connection Object by following method
proxoolConn.configure(props);// I just configured the Porperties object
proxoolConn.getConnection();
}
But no luck I just end-up with no exception in console .. I am using Struts 2, Hibernate and JasperReports.
Can any one help me to get the connection object from Hibernate?

The following code assumes you have an existing and open Hibernate org.hibernate.Session:
public void doWorkOnConnection(Session session) {
session.doWork(new Work() {
public void execute(Connection connection) throws SQLException {
//use the connection here...
}
});
}
Should you need information on how to use the above classes, please read the Hibernate 3.5 Javadoc. Specifically, read Session and then Work.

You can also downcast the Session method into a SessionImpl and get the connection object easily:
SessionImpl sessionImpl = (SessionImpl) session;
Connection conn = sessionImpl.connection();

How to put object in ThreadLocal in Struts 2?

I am trying to open Hibernate Session on each request and close it at the end.
This seems like it could work, but I have now idea how am I supposed to put my Session object in ThreadLocal and answer does not explain that.
Is there any Struts2 specific way to do this?

You can add a HttpFilter that is in front of the Struts2 Servlet. In the filter:
public class SessionProviderFilter implements Filter {
private static ThreadLocal<Session> sessionStore = new ThreadLocal<Session>();
public void doFilter(...) {
Session session = ... // get the session
sessionStore.set(session);
chain.doFilter(...);
sessionStore.set(null);
}
public static Session getCurrentSession() {
return sessionStore.get();
}
}
Now from any code, to get current hibernate session, you call SessionProviderFilter.getCurrentSession().

Hibernate connection problems

I'm working on a webapp and I have connection errors after Hibernate throws exceptions :
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.
It gave me this exception each time I try to access my db after an exception occured.
I now Hibernate's not supposed to throw errors if my application is well coded but if something happens with the connection to the db, I don't want my application to be stuck with this error.
Here's my HibernateUtil class :
public class HibernateUtil {
private static Logger log = Logger.getLogger(HibernateUtil.class);
private static org.hibernate.SessionFactory sessionFactory;
private static String confFile = "hibernate-test.properties";
private static final ThreadLocal<Session> threadSession = new ThreadLocal<Session>();
private HibernateUtil() {
}
public static void buildSessionFactory(){
Configuration configuration = new Configuration();
synchronized(HibernateUtil.class){
if(sessionFactory == null){
try {
Properties properties = new Properties();
properties.load(HibernateUtil.class.getClassLoader().getResourceAsStream(confFile));
configuration.setProperties(properties);
} catch (Exception e) {
log.fatal("cannot load the specified hibernate properties file: " + confFile);
throw new RuntimeException("cannot load the specified hibernate properties file : " + confFile, e);
}
sessionFactory = configuration.configure().buildSessionFactory();
}
HibernatePBEEncryptorRegistry registry = HibernatePBEEncryptorRegistry.getInstance();
if(registry.getPBEStringEncryptor("strongHibernateStringEncryptor") == null) {
StandardPBEStringEncryptor strongEncryptor = new StandardPBEStringEncryptor();
strongEncryptor.setAlgorithm("PBEWithMD5AndDES"); // not really needed as it is the default
strongEncryptor.setPassword("aStrongPassword");
registry.registerPBEStringEncryptor("strongHibernateStringEncryptor", strongEncryptor);
}
}
}
public static SessionFactory getSessionFactory() {
if(sessionFactory == null){
buildSessionFactory();
}
return sessionFactory;
}
public static Session getCurrentSession(){
if(!getSessionFactory().getCurrentSession().isOpen())
getSessionFactory().openSession();
return getSessionFactory().getCurrentSession();
}
}
Here's my BaseAction class where initialization and closing of sessions is set :
public class BaseAction extends ActionSupport {
public Session hib_session;
public void initHibSession() {
hib_session = HibernateUtil.getCurrentSession();
hib_session.beginTransaction();
hib_session.clear();
}
public void closeHibSession() {
hib_session.getTransaction().commit();
}
}
Here's an example of an action:
Transaction transaction = new Transaction(user, Transaction.Type.REGISTRATION, new HashSet(domains));
initHibSession();
hib_session.save(transaction);
closeHibSession();
transaction_id = transaction.getId();
Is there a way to avoid the exception above ?

It gave me this exception each time I try to access my db after an exception occurred.
I'm not sure to understand the exact condition. Anyway, after an exception, you should rollback the transaction, close the session and start over. That being said, I have some remarks about your code.
About your HibernateUtil:
why do you have a ThreadLocal, the Session#getCurrentSession() method handle that for you (you don't seem to use the thread local though).
in HibernateUtil.getCurrentSession(), why do you mess with getCurrentSession() and openSession()? Firstly, there is no need to do what you do, getCurrentSession() will return a new session if no session is associated to the current thread. Secondly, both approaches are different and have different semantics (you need to close the session yourself when using openSession()), you should use one or the other.
About your BaseAction:
I wonder why you clear() the session after Session#beginTransaction(). In case you didn't committed an ongoing transaction, you'll loose all the pending changes. Is this really what you want?
PS: I would consider using the Open Session in View pattern to remove all this burden from your code.
Resources
Sessions and transactions
Open Session in View