Let's assume that we have correctly configured JPA backed by Hibernate (version 4.3.11) in Spring (version 4.2.7). Hibernate first level cache is enabled. We use declarative transactions.
We have OuterBean:
#Service
public class OuterBean {
#Resource
private UserDao userDao;
#Resource
private InnerBean innerBean;
#Transactional(propagation = Propagation.NEVER)
public void withoutTransaction() {
User user = userDao.load(1l);
System.out.println(user.getName()); //return userName
innerBean.withTransaction();
user = userDao.load(1l);
System.out.println(user.getName()); //return userName instead of newUserName
}
}
And InnerBean that is called from OuterBean:
#Service
public class InnerBean {
#Resource
private UserDao userDao;
#Transactional
public void withTransaction() {
User user = userDao.load(1l);
user.setName("newUserName");
}
}
Is it correct behaviour that method user.getName() in OuterBean returns the same value twice (second time is after update name in database)?
In other words is it correct behaviour that #Transactional(propagation = Propagation.NEVER) creates Hibernate session for method withoutTransaction() that causes that second call user.getName() reads from Hibernate first level cache instead of database?
EDIT
To explain problem more I attache trace from creation of hibernate sessions
TRACE org.hibernate.internal.SessionFactoryImpl$SessionBuilderImpl - Opening Hibernate Session. tenant=null, owner=org.hibernate.jpa.internal.EntityManagerImpl#c17285e
TRACE org.hibernate.internal.SessionImpl - Opened session at timestamp: 14689173439
TRACE org.hibernate.internal.SessionImpl - Setting flush mode to: AUTO
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
userName
TRACE org.hibernate.internal.SessionFactoryImpl$SessionBuilderImpl - Opening Hibernate Session. tenant=null, owner=org.hibernate.jpa.internal.EntityManagerImpl#715c48ca
TRACE org.hibernate.internal.SessionImpl - Opened session at timestamp: 14689173439
TRACE org.hibernate.internal.SessionImpl - Setting flush mode to: AUTO
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Automatically flushing session
TRACE org.hibernate.internal.SessionImpl - before transaction completion
TRACE org.hibernate.internal.SessionImpl - after transaction completion
TRACE org.hibernate.internal.SessionImpl - Closing session
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
userName
TRACE org.hibernate.internal.SessionImpl - Closing session
Now let's compare trace when I remove #Transactional(propagation = Propagation.NEVER)
TRACE org.hibernate.internal.SessionFactoryImpl$SessionBuilderImpl - Opening Hibernate Session. tenant=null, owner=org.hibernate.jpa.internal.EntityManagerImpl#4ebd2c5f
TRACE org.hibernate.internal.SessionImpl - Opened session at timestamp: 14689203905
TRACE org.hibernate.internal.SessionImpl - Setting flush mode to: AUTO
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Closing session
userName
TRACE org.hibernate.internal.SessionFactoryImpl$SessionBuilderImpl - Opening Hibernate Session. tenant=null, owner=org.hibernate.jpa.internal.EntityManagerImpl#5af84083
TRACE org.hibernate.internal.SessionImpl - Opened session at timestamp: 14689203905
TRACE org.hibernate.internal.SessionImpl - Setting flush mode to: AUTO
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Automatically flushing session
TRACE org.hibernate.internal.SessionImpl - before transaction completion
TRACE org.hibernate.internal.SessionImpl - after transaction completion
TRACE org.hibernate.internal.SessionImpl - Closing session
TRACE org.hibernate.internal.SessionFactoryImpl$SessionBuilderImpl - Opening Hibernate Session. tenant=null, owner=org.hibernate.jpa.internal.EntityManagerImpl#35f4f41f
TRACE org.hibernate.internal.SessionImpl - Opened session at timestamp: 14689203906
TRACE org.hibernate.internal.SessionImpl - Setting flush mode to: AUTO
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Setting cache mode to: NORMAL
TRACE org.hibernate.internal.SessionImpl - Closing session
newUserName
Please notice when I omit #Transactional(propagation = Propagation.NEVER) separate session is create for every invocation of method from userDao.
So my question can be formulated also as
Shouldn’t be #Transactional(propagation = Propagation.NEVER)
implemented in Spring as a guardian that prevents us from accidental use of
transaction, without any side effect (session creation)?
The behavior is correct - Hibernate will always create a session (how else would you expect it to perform any operation?), and by loading the entity you have associated it with that session. Since withoutTransaction is not participating in a transaction, the changes made within withTransaction will happen within a new transaction and shouldn't be visible unless you call refresh, which will force a re-load from the database.
I'm quoting Hibernate's official documentation:
The main function of the Session is to offer create, read and delete operations for instances of mapped entity classes. Instances may exist in one of three states:
transient: never persistent, not associated with any Session
persistent: associated with a unique Session detached: previously
persistent, not associated with any Session
Transient instances may be made persistent by calling save(), persist() or saveOrUpdate(). Persistent instances may be made transient by calling delete(). Any instance returned by a get() or load() method is persistent.
Taken from Java Persistence With Hibernate, Second Edition by Christian Bauer, Gavin King, and Gary Gregory:
The persistence context acts as a first-level cache; it remembers all entity instances you’ve handled in a particular unit of work. For example, if you ask Hibernate to load an entity instance using a primary key value (a lookup by identifier), Hibernate can first check the current unit of work in the persistence context. If Hibernate finds the entity instance in the persistence context, no database hit occurs—this is a repeatable read for an application. Consecutive em.find(Item.class, ITEM_ID) calls with the same persistence context will yield the same result.
Also from Java Persistence With Hibernate, Second Edition:
The persistence context cache is always on—it can’t be turned off. It ensures the following:
The persistence layer isn’t vulnerable to stack overflows in the case of circular references in an object graph.
There can never be conflicting representations of the same database row at the end of a unit of work. The provider can safely write all changes made to an entity instance to the database.
Likewise, changes made in a particular persistence context are always immediately visible to all other code executed inside that unit of work and its persistence context. JPA guarantees repeatable entity-instance reads.
Concerning transactions, here's an excerpt taken from official Hibernate's documentation:
Defines the contract for abstracting applications from the configured underlying means of transaction management. Allows the application to define units of work, while maintaining abstraction from the underlying transaction implementation (eg. JTA, JDBC).
So, to sum it up, withTransaction and withoutTransaction will not share UnitOfWork and therefore will not share the first-level cache, which is why the second load returns the original value.
As to the reasons why these two methods do not share the unit of work, you can refer to Shailendra's answer.
EDIT:
You seem to misunderstand something. A session must always be created - that's how Hibernate works, period. Your expectation of no sessions being created is equal to expecting to execute a JDBC query without having a JDBC connection :)
The difference between your two examples is that with #Transactional(propagation = Propagation.NEVER) your method is intercepted and proxied by Spring and only a single session is created for the queries in withoutTransaction. When you remove the annotation you exclude your method from Spring's transactional interceptor so a new session will be created for each DB-related operation. I repeat again, and I cannot stress this enough - you must have an open session to perform any queries.
As far as guarding goes - try swapping the annotations on the two methods by making withTransaction use Propagation.NEVER and withoutTransaction use the default #Transactional annotation and see what happens (spoiler: you'll get an IllegalTransactionStateException).
EDIT2:
As for why the session is shared between two loads in the outer bean - that's just what JpaTransactionManager is supposed to do, and by annotating your method with #Transactional you've notified Spring that it should use the configured transaction manager to wrap your method. Here's what the official documentation says about JpaTransactionManager's expected behavior:
PlatformTransactionManager implementation for a single JPA EntityManagerFactory. Binds a JPA EntityManager from the specified factory to the thread, potentially allowing for one thread-bound EntityManager per factory. SharedEntityManagerCreator and #PersistenceContext are aware of thread-bound entity managers and participate in such transactions automatically. Using either is required for JPA access code supporting this transaction management mechanism.
Also, to know how Spring is handling declarative transaction management (i.e. #Transactional annotations on methods), refer to the official documentation. For ease of navigation, I'll include a quote:
The most important concepts to grasp with regard to the Spring Framework’s declarative transaction support are that this support is enabled via AOP proxies, and that the transactional advice is driven by metadata (currently XML- or annotation-based). The combination of AOP with transactional metadata yields an AOP proxy that uses a TransactionInterceptor in conjunction with an appropriate PlatformTransactionManager implementation to drive transactions around method invocations.
First of all, as you use hibernate behind JPA API I will use the term EntityManager instead of session (strictly the same thing, just a matter of terminology).
Every access to the database using JPA will involve an EntityManager, you are fetching entities, you need an EntityManager (EM). What's called 1st level cache is nothing more than the EM managed entities state.
Theoretically the lifecycle of the EM is short and bound to a unit of work (and so generally to a transaction, see Struggling to understand EntityManager proper use).
Now JPA can be used in different way : Container-Managed or User-Managed persistence. When the EM is managed by the container (your case, here spring is the container) this last is in charge of managing the EM scope / lifecycle (create, flush and destroy it for you). As the EM is bounded to a transaction / Unit of Work, this task is delegated to the TransactionManager (the object handling the #Transactional annotations).
When you annotate a method using #Transactional(propagation = Propagation.NEVER), you are creating a spring logical transaction scope which will ensure that there is no existing underlying JDBC transaction bound to an eventual existing EM, which will not create one and will use JDBC autocommit mode but which will create an EM for this logical transaction scope if none already exists.
Regarding the fact that a new EM instance is created for each DAO call when no transaction logical scope is defined, you have to remember that you cannot access database using JPA outside of the EM. AFAIK hibernate used to throw a no session bound to thread error in this case but this may have evolved with later releases, otherwise your DAO may be annotated with #Transactional(propagation = Propagation.SUPPORT) which would also automatically create an EM if no enclosing logical scope exists. This is a bad practice as transaction should be defined at the unit of work, eg. the service level and not the DAO one.
#Transactional(propagation = Propagation.NEVER) would still create a session. If you are using Spring/Hibernate/JPA combination for non distributed transactions then you are most certainly using JpaTransactionManager as the Spring
transaction manager. The answer to your question lies in this class. A good idea would be do use a debugger in your IDE to follow what's happening. The doBegin method of this class ( which is called by Spring transaction infrastructure is :-
protected void doBegin(Object transaction, TransactionDefinition definition) {
JpaTransactionObject txObject = (JpaTransactionObject) transaction;
if (txObject.hasConnectionHolder() && !txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
throw new IllegalTransactionStateException(
"Pre-bound JDBC Connection found! JpaTransactionManager does not support " +
"running within DataSourceTransactionManager if told to manage the DataSource itself. " +
"It is recommended to use a single JpaTransactionManager for all transactions " +
"on a single DataSource, no matter whether JPA or JDBC access.");
}
try {
if (txObject.getEntityManagerHolder() == null ||
txObject.getEntityManagerHolder().isSynchronizedWithTransaction()) {
EntityManager newEm = createEntityManagerForTransaction();
if (logger.isDebugEnabled()) {
logger.debug("Opened new EntityManager [" + newEm + "] for JPA transaction");
}
txObject.setEntityManagerHolder(new EntityManagerHolder(newEm), true);
}
EntityManager em = txObject.getEntityManagerHolder().getEntityManager();
// Delegate to JpaDialect for actual transaction begin.
final int timeoutToUse = determineTimeout(definition);
Object transactionData = getJpaDialect().beginTransaction(em,
new DelegatingTransactionDefinition(definition) {
#Override
public int getTimeout() {
return timeoutToUse;
}
});
txObject.setTransactionData(transactionData);
// Register transaction timeout.
if (timeoutToUse != TransactionDefinition.TIMEOUT_DEFAULT) {
txObject.getEntityManagerHolder().setTimeoutInSeconds(timeoutToUse);
}
// Register the JPA EntityManager's JDBC Connection for the DataSource, if set.
if (getDataSource() != null) {
ConnectionHandle conHandle = getJpaDialect().getJdbcConnection(em, definition.isReadOnly());
if (conHandle != null) {
ConnectionHolder conHolder = new ConnectionHolder(conHandle);
if (timeoutToUse != TransactionDefinition.TIMEOUT_DEFAULT) {
conHolder.setTimeoutInSeconds(timeoutToUse);
}
if (logger.isDebugEnabled()) {
logger.debug("Exposing JPA transaction as JDBC transaction [" +
conHolder.getConnectionHandle() + "]");
}
TransactionSynchronizationManager.bindResource(getDataSource(), conHolder);
txObject.setConnectionHolder(conHolder);
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Not exposing JPA transaction [" + em + "] as JDBC transaction because " +
"JpaDialect [" + getJpaDialect() + "] does not support JDBC Connection retrieval");
}
}
}
// Bind the entity manager holder to the thread.
if (txObject.isNewEntityManagerHolder()) {
TransactionSynchronizationManager.bindResource(
getEntityManagerFactory(), txObject.getEntityManagerHolder());
}
txObject.getEntityManagerHolder().setSynchronizedWithTransaction(true);
}
catch (TransactionException ex) {
closeEntityManagerAfterFailedBegin(txObject);
throw ex;
}
catch (Throwable ex) {
closeEntityManagerAfterFailedBegin(txObject);
throw new CannotCreateTransactionException("Could not open JPA EntityManager for transaction", ex);
}
}
The transactional resource when using JPA is actually the entity manager (underlying implementation is session in hibernate) as you can see and this is the first thing this method does
EntityManager em = txObject.getEntityManagerHolder().getEntityManager();
So definitely an entity manager / session is created. The transaction attributes are then passed to the underlying JpaDialect (HibernateJpaDialect) via TransactionDefinition. This class in turn actually gets the underlying Hibernate Session and the transaction API of session.
HibernateJpaDialect {
........
public Object beginTransaction(EntityManager entityManager, TransactionDefinition definition)
Session session = getSession(entityManager);
entityManager.getTransaction().begin();
......
......
}
......
I don't think this is correct behavior. It is true what the colleagues are saying that even without transaction the hibernate is creating a session. But this mean that we are facing two sessions S1 and S2 for the two separate reads from the DAO. At the same time L1 cache is always per session, so it does not make sense for two separate sessions to have a hit for the L1 cache. It seems like your Spring is not respecting the #Transactional(propagation = Propagation.NEVER)
The #Transactional(propagation = Propagation.NEVER) should be equivalent to if you just initialize your service from a main method and do the subsequent calls to the DAO yourself.
Try it in a main class and see how it will react. I doubt it will hit the L1 cache again.
Also I will copy paste the doc from Sprint on propagation NEVER:
NEVER Execute non-transactionally, throw an exception if a transaction
exists.
One more question - Is the hibernate configured to AutoCommit. Is it possible that the "runInTransaction" - method is not committing ?
Related
I have a spring managed web app where we're using Hibernate. In my hibernate.cfg.xml we have
<property name="hibernate.current_session_context_class">thread</property>
It's also configured to use HikariCP connection pooling.
When we open sessions, we follow the paradigm of this. Note that I'm not explicitly closing the session.
Transaction tx = null;
Session session = sessionFactory.getCurrentSession();
try {
tx = session.beginTransaction();
// do DB stuff.
tx.commit(); // or, sometimes session.getTransaction().commit();
} catch (Exception e) {
if (tx != null) {
tx.rollback();
}
throw new CustomDbException(e);
}
In some cases, when closing the session, we do session.getTransaction().commit() at a minimum, this is incosistent, but I'm not sure if it's giving a different trasancation or otherwise causing some problems.
We've been seeing intermittent issues with LockAcquisitionException: could not execute statement, StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect), and TransactionException: nested transactions not supported. We're not trying to do nested exceptiosn and always clean up the transaction, but I'm starting to think that maybe the sessions is being shared.
The application is multi threaded, and I'm starting to suspect that getCurrentSession is actually being shread across threads. I was under the impression that by setting hibernate.current_session_context_class to thread, then getCurrentSession() would provide a separate session per thread. Should I be taking a different approach here? Should I be using openSession() instead, or somehow configuring hibernate to give me unique sessions per thread?
We use #JmsListener methods, and the transactional exceptions seem most prevalent there, but are not localized there.
Exact hibernate versions are as follows:
hibernate: [ 'org.hibernate.common:hibernate-commons-annotations:4.0.4.Final',
'org.hibernate:hibernate-core:4.3.11.Final',
'org.hibernate:hibernate-hikaricp:4.3.11.Final'],
hikari: 'com.zaxxer:HikariCP:2.4.1',
I have a very weird error working with Spring JPA transactions. The thread is locked around 16 minutes and then continues without any problem.
Here is the situation:
#Transactional(propagation = Propagation.REQUIRES_NEW)
public class A {
public String encrypt(String str){
LOG.debug("encrypting...");
// just data base read operations
}
public String encrypt(String str, String str2){
// read and write database operations.
}
public String foo(...){
// read and write database operations.
}
public String bar(...){
// read and write database operations.
}
}
#Transactional(propagation = Propagation.REQUIRES_NEW)
public class B {
public String doSomething(...){
LOG.debug("calling encrypt method...");
String chain1 = this.a.encrypt("whatever");
LOG.debug("calling encrypt method...");
String chain2 = this.a.encrypt("again");
LOG.debug("calling encrypt method...");
String chain3 = this.a.encrypt("and again");
...
}
}
Taking a look to the log file I see that it takes 16 minutes from log "calling encrypt method" to "encripting". So, have activated JTA logs and this is what I see:
15:09:04.317 DEBUG e.i.n.p.d.TipoMensajeDaoDelegate [45] - obteniendo mensaje para tipo operacion 0104 y protocolo 03
15:09:04.318 DEBUG o.s.orm.jpa.JpaTransactionManager [332] - Found thread-bound EntityManager [org.hibernate.ejb.EntityManagerImpl#4e6b01e9] for JPA transaction
15:09:04.319 DEBUG o.s.orm.jpa.JpaTransactionManager [471] - Participating in existing transaction
15:09:04.320 DEBUG o.s.orm.jpa.JpaTransactionManager [332] - Found thread-bound EntityManager [org.hibernate.ejb.EntityManagerImpl#4e6b01e9] for JPA transaction
15:09:04.321 DEBUG o.s.orm.jpa.JpaTransactionManager [471] - Participating in existing transaction
15:09:04.324 DEBUG e.i.n.c.p.p.b.B [485] - calling encrypt method...
15:09:04.325 DEBUG o.s.orm.jpa.JpaTransactionManager [332] - Found thread-bound EntityManager [org.hibernate.ejb.EntityManagerImpl#4e6b01e9] for JPA transaction
15:09:04.326 DEBUG o.s.orm.jpa.JpaTransactionManager [416] - Suspending current transaction, creating new transaction with name [es.indra.nnp.gestorclaves.GestorClavesServiceImpl.cifrar]
15:09:04.326 DEBUG o.s.orm.jpa.JpaTransactionManager [369] - Opened new EntityManager [org.hibernate.ejb.EntityManagerImpl#27f2b012] for JPA transaction
...
15:24:29.954 DEBUG o.s.orm.jpa.JpaTransactionManager [408] - Not exposing JPA transaction [org.hibernate.ejb.EntityManagerImpl#27f2b012] as JDBC transaction because JpaDialect [org.springframework.orm.jpa.DefaultJpaDialect#4d832b01] does not support JDBC Connection retrieval
15:24:29.955 DEBUG e.i.n.g.A [146] - encrypting
15:24:29.956 DEBUG o.s.orm.jpa.JpaTransactionManager [332] - Found thread-bound EntityManager [org.hibernate.ejb.EntityManagerImpl#27f2b012] for JPA transaction
15:24:29.957 DEBUG o.s.orm.jpa.JpaTransactionManager [471] - Participating in existing transaction
15:24:29.958 DEBUG o.s.orm.jpa.JpaTransactionManager [332] - Found thread-bound EntityManager [org.hibernate.ejb.EntityManagerImpl#27f2b012] for JPA transaction
15:24:29.958 DEBUG o.s.orm.jpa.JpaTransactionManager [471] - Participating in existing transaction
15:24:29.962 DEBUG o.s.orm.jpa.JpaTransactionManager [332] - Found thread-bound EntityManager [org.hibernate.ejb.EntityManagerImpl#27f2b012] for JPA transaction
15:24:29.962 DEBUG o.s.orm.jpa.JpaTransactionManager [471] - Participating in existing transaction
...
Here, the facts:
Error does not happen always, but when it does it is always in the same point.
After 16 minutes more or less, the thread continues and calls the same method few times with no problem and finish correctly.
When it happens, it is always around 15 minutes and 30 seconds.
It happens with no concurrency. Anyway, when a thread is locked, if I start another thread there is no problem. The second thread is processed while the first is still locked.
DDBB has being checked looking for database locks while the lock was happening. No database locks were found.
Others methods form class A are called from others points of the code with no problem.
Just happens on production environment. You can imagine how difficult is to do changes.
Database connection is done via JNDI to MySql and application run in Tomcat.
I know that with this information is difficult to find out where the problem is. Just I hope someone can contribute with some thoughts that help me to find what is happening.
For me this sounds pretty much like this SO question.
Using REQUIRES_NEW will always ensure a new Transaction, so if there is an already existing one that should be suspended.
But since nested transactions are not supported by the JPATransactionManager:
On JDBC 3.0, this transaction manager supports nested transactions via
JDBC 3.0 Savepoints. The
AbstractPlatformTransactionManager.setNestedTransactionAllowed(boolean)
"nestedTransactionAllowed"} flag defaults to "false", though, as
nested transactions will just apply to the JDBC Connection, not to the
JPA EntityManager and its cached objects. You can manually set the
flag to "true" if you want to use nested transactions for JDBC access
code which participates in JPA transactions (provided that your JDBC
driver supports Savepoints). Note that JPA itself does not support
nested transactions! Hence, do not expect JPA access code to
semantically participate in a nested transaction.
So the two transactions will share the same JDBC connection and there might be some locking involved. Is it that the transaction timeout is set to 15 minutes and that's why you see it hanging around for this amount of time?
I had a web software running in a Jboss AS 7 container witch saves our data in a PostgreSQL 9.1 database via JPA, an its configuration delegated to JTA.
Last year it was adapted to run at AWS EC2 cloud. As the user demand grown our database usage growed too. As expected our database server becomes busy at rush times, an it affected the usage experience from our users.
After some replication researches on PostgreSQL we realise that PGPool2 could be a nice replication solution for our case: it offers Load Balancing for SELECT queries, and Replication for CUD operations ( UPDATE, INSERT and DELETE ) as well.
So far so good, except that it turns the software slow. If fact, as explicited in PGPool2 documentation, SELECT queries will not be load balanced if it was defined in explicit BEGIN/END transaction.
For a query to be load balanced, all the following requirements must be met:
- PostgreSQL version 7.4 or later
- the query must not be in an explicitly declared transaction (i.e. not in a BEGIN ~ END block)
- it's not SELECT nextval or SELECT setval
- it's not SELECT INTO
- it's not SELECT FOR UPDATE nor FOR SHARE
- it starts with "SELECT" or one of COPY TO STDOUT, EXPLAIN, EXPLAIN ANALYZE SELECT...
- ignore_leading_white_space = true will ignore leading white space.
Two questions:
How I could figure out our SELECT queries that was running in explicit transactions?
Does _javax.ejb.TransactionAttributeType.NOT_SUPPORTED_ fix the transaction scopes, granting that my SELECT method will be running as "transaction-free"?
How I could figure out our SELECT queries that was running in explicit transactions?
Turn on pgpool2 logging of SQL and connections:
Put the following statements into pgpool.conf (which you can setup via cp $prefix/etc/pgpool.conf.sample $prefix/etc/pgpool.conf):
log_per_node_statement
log_connections
Alternatively, turn on log tracing of JPA:
This requires a different method depending or your JPA implementation ( How to view the SQL queries issued by JPA? , JPA 2.0 (logging and tracing through) with Glassfish 3.0.1 and NetBeans 6.9.1: ).
This will log SQL, but will not log transaction start/commit/rollback.
Additionally, put your own debug logging code into methods which start & end transactions, so that you can see when transaction start/commit/rollback.
Does _javax.ejb.TransactionAttributeType.NOT_SUPPORTED_ fix the transaction scopes, granting that my SELECT method will be running as "transaction-free"?
If you are using Container Managed Transactions (annotations #TransactionManagement(CONTAINER) and #TransactionAttribute), then NOT_SUPPORTED will temporarily disassocate the JTA transaction from the current thread. Then the method will run with no transaction context.
Your subsequent JPA query will run outside of the JTA transaction - because the JTA transaction is not available for it to use.
If you already use a Transaction-Scoped EntityManager
Within your Stateless Session Bean you have an EntityManager annotated
#PersistenceContext(type=PersistenceContextType.TRANSACTION), or
annotated #PersistenceContext without type attribute (because
TRANSACTION is the default):
then that EM will lose it's persistence context within the NOT_SUPPORTED method because the PC is associated with the current transaction, which is no longer accessible
so you cannot use such an EM in the method (e.g. to run queries or lookup cached objects)
so you must use an additional application-managed EM within the NOT_SUPPORTED method
you must create the app-managed EM from an EntityManagerFactory in a place where no JTA transaction is active (e.g. in the NOT_SUPPORTED method), because the app-managed EM will automatically associate itself with the current thread's JTA transaction during creation
any objects returned from queries by the new app-managed EM will be in a different persistence context from the original EM, so you need great care to cleanly detach such objects from the PC (e.g. appMgdEM.clear() or appMgdEM.close() or appMgdEM.detach(someEntity)) if you are to modify/merge them with the original EM.
If you already use an Extended-Scoped EntityManager
Within your Stateful Session Bean you have an EntityManager annotated #PersistenceContext(type=PersistenceContextType.EXTENDED).
then that EM will still have it's persistence context within the NOT_SUPPORTED method because the PC is associated with the stateful session bean
but the EM is using a connection that is already in the middle of a "live" transaction
so if you want to run queries outside of a transaction, you cannot use such an EM in the method
so again, you must use an additional application-managed EM within the NOT_SUPPORTED method (same points apply as above).
Example
#Stateless
public class DepartmentManagerBean implements DepartmentManager {
#PersistenceUnit(unitName="EmployeeService")
EntityManager txScopedEM;
#PersistenceUnit(unitName="EmployeeService")
EntityManagerFactory emf;
#TranactionAttribute(REQUIRED)
public void modifyDepartment(int deptId) {
Department dept = txScopedEM.find(Department.class, deptId);
dept.setName("New Dept Name");
List<Employee> empList = getEmpList();
for(Employee emp : empList) {
txScopedEM.merge(emp);
dept.addEmployee(emp);
}
dept.setEmployeeCount(empList.size());
}
#TranactionAttribute(NOT_SUPPORTED)
public void getEmpList() {
EntityManager appManagedEM = emf.createEntityManager();
TypedQuery<Employee> empQuery = appManagedEM.createQuery("...", Employee.class);
List<Employee> empList = empQuery.getResultList();
// ...
appManagedEM.clear();
return empList;
}
}
Alternative/Adjusted Approach
The above has some restrictions on how you query and how you use resulting objects. It requires creating an EM "on the fly", if you use stateless session beans, and also requires entityManager.merge() to be called. It may not suit you.
A strong alternative is to redesign your application, so that you run all queries before the transaction starts. Then it should be possible to use a single Extended-Scoped EntityManager. Run the queries in "NOT_SUPPORTED" method 1 (no transaction), using extended-scope EM. Then run modifications in "REQUIRED" method 2 (with transaction), using the same extended-scope EM. A Transaction-Scoped EntityManaged wouldn't work (it would try to be transactional from the very start, and would have no PC in NOT_SUPPORTED methods).
Cheers :)
You may want to consider partitioning in JPA using EclipseLink data partitioning,
http://java-persistence-performance.blogspot.com/2011/05/data-partitioning-scaling-database.html
I had been using #Transactional annotations in my Service Layer. But to resolve an error due to Lazy Loading in View I had to use Open Session in View Filter. After this, without use of #Transaction itself a Session gets opened and transaction starts. So does that mean #Transactions are not required? How will transactions and roll-backs be handled, then in Service Layers?
The javadoc explains it:
This filter makes Hibernate Sessions available via the current thread, which will be autodetected by transaction managers. It is suitable for service layer transactions via HibernateTransactionManager or JtaTransactionManager as well as for non-transactional execution (if configured appropriately).
NOTE: This filter will by default not flush the Hibernate Session, with the flush mode set to FlushMode.NEVER. It assumes to be used in combination with service layer transactions that care for the flushing: The active transaction manager will temporarily change the flush mode to FlushMode.AUTO during a read-write transaction, with the flush mode reset to FlushMode.NEVER at the end of each transaction. If you intend to use this filter without transactions, consider changing the default flush mode (through the "flushMode" property).
I am currently using version 3.3 of hibernate.
Currently the setting of hibernate is such that it will autocommit after each persistence of individual object.
I want to wrap a transaction around it, so it will only commit after end of a batch.
The code is in question:
getHibernateTemplate().saveOrUpdateAll(collectionOfObject);
I have consulted the documentation here, but want to see if there is alternative (other than rewriting it to use HSQL)
EDIT
My goal is to have a transaction around a bunch of insert. Currently it is auto-commit per insert
If you want to use transaction management in Spring read here on how to do it.
Also, Use should not be using HibernateTemplate use the Session object instead as below.
sessionFactory = getHibernateTemplate().getSessionFactory();
Session session = sessionFactory.getCurrentSession();
for (Bean bean : listBeans) {
session.saveOrUpdate(bean );
}
As there is no way to save the collection at one shot in session. This will commit the data after method exit.