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Getting "org.hibernate.LazyInitializationException" exceptions after retrieving items from my second-level ehcache

I'm using Hibernate 5.1.0.Final with ehcache and Spring 3.2.11.RELEASE. I have the following #Cacheable annotation set up in one of my DAOs:
#Override
#Cacheable(value = "main")
public Item findItemById(String id)
{
return entityManager.find(Item.class, id);
}
The item being returned has a number of assocations, some of which are lazy. So for instance, it (eventually) references the field:
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(name = "product_category", joinColumns = { #JoinColumn(name = "PRODUCT_ID") }, inverseJoinColumns = { #JoinColumn(name = "CATEGORY_ID") })
private List<Category> categories;
I notice that within one of my methods that I mark as #Transactional, when the above method is retrieved from the second level cache, I get the below exception when trying to iterate over the categories field:
#Transactional(readOnly=true)
public UserContentDto getContent(String itemId, String pageNumber) throws IOException
{
Item Item = contentDao.findItemById(ItemId);
…
// Below line causes a “LazyInitializationException” exception
for (Category category : item.getParent().getProduct().getCategories())
{
The stack trace is:
16:29:42,557 INFO [org.directwebremoting.log.accessLog] (ajp-/127.0.0.1:8009-18) Method execution failed: : org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: org.mainco.subco.ecom.domain.Product.standardCategories, could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:579) [hibernate-myproject-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:203) [hibernate-myproject-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:558) [hibernate-myproject-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:131) [hibernate-myproject-5.1.0.Final.jar:5.1.0.Final]
at org.hibernate.collection.internal.PersistentBag.iterator(PersistentBag.java:277) [hibernate-myproject-5.1.0.Final.jar:5.1.0.Final]
at org.mainco.subco.ebook.service.ContentServiceImpl.getCorrelationsByItem(ContentServiceImpl.java:957) [myproject-90.0.0-SNAPSHOT.jar:]
at org.mainco.subco.ebook.service.ContentServiceImpl.getContent(ContentServiceImpl.java:501) [myproject-90.0.0-SNAPSHOT.jar:]
at sun.reflect.GeneratedMethodAccessor819.invoke(Unknown Source) [:1.6.0_65]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) [rt.jar:1.6.0_65]
at java.lang.reflect.Method.invoke(Method.java:597) [rt.jar:1.6.0_65]
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317) [spring-aop-3.2.11.RELEASE.jar:3.2.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183) [spring-aop-3.2.11.RELEASE.jar:3.2.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150) [spring-aop-3.2.11.RELEASE.jar:3.2.11.RELEASE]
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96) [spring-tx-3.2.11.RELEASE.jar:3.2.11.RELEASE]
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260) [spring-tx-3.2.11.RELEASE.jar:3.2.11.RELEASE]
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94) [spring-tx-3.2.11.RELEASE.jar:3.2.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) [spring-aop-3.2.11.RELEASE.jar:3.2.11.RELEASE]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:91) [spring-aop-3.2.11.RELEASE.jar:3.2.11.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) [spring-aop-3.2.11.RELEASE.jar:3.2.11.RELEASE]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204) [spring-aop-3.2.11.RELEASE.jar:3.2.11.RELEASE]
at com.sun.proxy.$Proxy126.getContent(Unknown Source)
I understand what the Hibernate session is closed — I do not care about why this happens. Also, it is NOT an option o make the above association eager (instead of lazy). Given that, how can I solve this problem?
Edit: Here is how my ehccahe.xml is configured …
<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../config/ehcache.xsd" updateCheck="false">
<!-- This is a default configuration for 256Mb of cached data using the JVM's heap, but it must be adjusted
according to specific requirement and heap sizes -->
<defaultCache maxElementsInMemory="10000"
eternal="false"
timeToIdleSeconds="86400"
timeToLiveSeconds="86400"
overflowToDisk="false"
memoryStoreEvictionPolicy="LRU">
</defaultCache>
<cache name="main" maxElementsInMemory="10000" />
<cacheManagerPeerProviderFactory
class="net.sf.ehcache.distribution.RMICacheManagerPeerProviderFactory"
properties="peerDiscovery=automatic, multicastGroupAddress=230.0.0.1,
multicastGroupPort=4446, timeToLive=32"/>
<cacheManagerPeerListenerFactory
class="net.sf.ehcache.distribution.RMICacheManagerPeerListenerFactory"
properties="hostName=localhost, port=40001,
socketTimeoutMillis=2000"/>
</ehcache>
and here is how I’m plugging it into my Spring context …
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="packagesToScan" value="org.mainco.subco" />
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"/>
</property>
<property name="dataSource" ref="dataSource"/>
<property name="jpaPropertyMap" ref="jpaPropertyMap" />
</bean>
<cache:annotation-driven key-generator="cacheKeyGenerator" />
<bean id="cacheKeyGenerator" class="org.mainco.subco.myproject.util.CacheKeyGenerator" />
<bean id="cacheManager"
class="org.springframework.cache.ehcache.EhCacheCacheManager"
p:cacheManager-ref="ehcache"/>
<bean id="ehcache" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean"
p:configLocation="classpath:ehcache.xml"
p:shared="true" />
<util:map id="jpaPropertyMap">
<entry key="hibernate.show_sql" value="false" />
<entry key="hibernate.hbm2ddl.auto" value="validate"/>
<entry key="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect"/>
<entry key="hibernate.transaction.manager_lookup_class" value="org.hibernate.transaction.JBossTransactionManagerLookup" />
<entry key="hibernate.cache.region.factory_class" value="org.hibernate.cache.ehcache.EhCacheRegionFactory"/>
<entry key="hibernate.cache.provider_class" value="org.hibernate.cache.EhCacheProvider"/>
<entry key="hibernate.cache.use_second_level_cache" value="true" />
<entry key="hibernate.cache.use_query_cache" value="false" />
<entry key="hibernate.generate_statistics" value="false" />
</util:map>
<bean id="entityManager" class="org.springframework.orm.jpa.support.SharedEntityManagerBean">
<property name="entityManagerFactory" ref="entityManagerFactory"/>
</bean>

Take a look at a similar question. Basically, your cache is not a Hibernate second-level cache. You are accessing a lazy uninitialized association on a detached entity instance, so a LazyInitializationException is expected to be thrown.
You can try to play around with hibernate.enable_lazy_load_no_trans, but the recommended approach is to configure Hibernate second level cache so that:
Cached entities are automatically attached to the subsequent sessions in which they are loaded.
Cached data is automatically refreshed/invalidated in the cache when they are changed.
Changes to the cached instances are synchronized taking the transaction semantics into consideration. Changes are visible to other sessions/transactions with the desired level of cache/db consistency guarantees.
Cached instances are automatically fetched from the cache when they are navigated to from the other entities which have associations with them.
EDIT
If you nevertheless want to use Spring cache for this purpose, or your requirements are such that this is an adequate solution, then keep in mind that Hibernate managed entities are not thread-safe, so you will have to store and return detached entities to/from the custom cache. Also, prior to detachment you would need to initialize all lazy associations that you expect to be accessed on the entity while it is detached.
To achieve this you could:
Explicitly detach the managed entity with EntityManager.detach. You would need to detach or cascade detach operation to the associated entities also, and make sure that the references to the detached entities from other managed entities are handled appropriately.
Or, you could execute this in a separate transaction to make sure that everything is detached and that you don't reference detached entities from the managed ones in the current persistence context:
#Override
#Cacheable(value = "main")
#Transactional(propagation = Propagation.REQUIRES_NEW)
public Item findItemById(String id) {
Item result = entityManager.find(Item.class, id);
Hibernate.initialize(result.getAssociation1());
Hibernate.initialize(result.getAssociation2());
return result;
}
Because it may happen that the Spring transaction proxy (interceptor) is executed before the cache proxy (both have the same default order value: transaction; cache), then you would always start a nested transaction, be it to really fetch the entity, or to just return the cached instance.
While we may conclude that performance penalty for starting unneeded nested transactions is small, the issue here is that you leave a small time window when a managed instance is present in the cache.
To avoid that, you could change the default order values:
<tx:annotation-driven order="200"/>
<cache:annotation-driven order="100"/>
so that cache interceptor is always placed before the transaction one.
Or, to avoid ordering configuration changes, you could simply delegate the call from the #Cacheable method to the #Transactional(propagation = Propagation.REQUIRES_NEW) method on another bean.

What you implemented in your code snippets is a custom cache based on spring-cache. With your implementation you would need to take care of cache evictions, making sure that at the point when your object graphs will get cached they are properly loaded, etc. Once they get cached and the original hibernate session that loaded them is closed they'll become detached, you can no longer navigate unfetched lazy associations. Also, your custom cache solution in its current state would cache entity graphs, which is probably not what you want, since any part of that graph might change at a given time, and your cache solution would need to watch for changes in all parts of that graph to properly handle evictions.
The configuration you posted in your question is not Hibernate second-level cache.
Managing a cache is a complex endeavor and I don't recommend it doing it by yourself, unless you're absolutely sure what you're doing (but then you won't be asking this question on Stackoverflow).
Let me explain what is happening with when you get the LazyInitializationException: you marked one of your dao methods with #org.springframework.cache.annotation.Cacheable. What happens in this case is the following:
Spring attaches an interceptor to your managed bean. The interceptor will intercept the dao method call, it will create a cache key based on the interceptor method and the actual method arguments (this can be customized), and look up the cache to see if there's any entry in the cache for that key. In case there's an entry it will return that entry without actually invoking your method. In case there's no cache entry for that key, it will invoke your method, serializes the return value and store it in the cache.
For the case when there was no cache entry for the key, your method will get invoked. Your method uses a spring provided singleton proxy to the thread bound EntityManager which was assigned earlier when Spring encountered the first #Transactional method invocation. In your case this was the getContent(...) method of another spring service bean. So your method loads an entity with EntityManager.find(). This will give you a partially loaded entity graph containing uninitialized proxies and collections to other associated entities not yet loaded by the persistence context.
Your method returns with the partially loaded entity graph and spring will immediately serialize it for you and store it in the cache. Note that serializing a partially loaded entity graph will deserialize to a partially loaded entity graph.
On the second invocation of the dao method marked with #Cacheable with the same arguments, Spring will find that there is indeed an entry in the cache corresponding to that key and will load and deserialize the entry. Your dao method will not be called since it uses the cached entry. Now you encounter the problem: your deserialized cached entity graph was only partially loaded when you stored in the cache, and as soon as you touch any uninitialized part of the graph you'll get the LazyInitializationException. A deserialized entity will always be detached, so even if the original EntityManager would be still open (which is not), you would still get the same exception.
Now the question is: what can you do to avoid the LazyInitializationException. Well, my recommendation is that you forget about implementing a custom cache and just configure Hibernate to do the caching for you. I will talk about how to do that later. If you want to stick with the custom cache you tried to implement, here's what you need to do:
Go through your whole code base and find all invocations of your #Cacheable dao method. Follow all possible code paths where the loaded entity graph is passed around and mark all parts of the entity graph which ever gets touched by client code. Now go back to your #Cacheable method and modify it so that it loads and initializes all parts of the entity graph that would ever get possibly touched. Because once you return it and it gets serialized, and deserialized later, it will always be in a detached state so better make sure all possible graph paths are properly loaded. You should already feel how impractical this will end up. If that still didn't convince you not to follow this direction, here's another argument.
Since you load up a potentially big chunk of the database, you will have a snapshot of that part of the database at the given time when it got actually loaded and cached. Now, whenever you use a cached version of this big chunk of the database, there's is a risk that you are using a stale version of that data. To defend from this, you would need to watch for any changes in the current version of that big chunk of the database you just cached and evict the whole entity graph from the cache. So you pretty much need to take into account which entities are parts of your entity graph and set up some event listeners whenever those entities are changed and evict the whole graph. None of these issues are present with Hibernate second-level cache.
Now back to my recommendation: set up Hibernate second-level cache
Hibernate second-level cache is managed by Hibernate and you get eviction management from hibernate automatically. If you have Hibernate second-level cache enabled, Hibernate will cache the data needed to reconstruct your entities and, if - when seeking to load an entity from the database - it finds that it has a valid cache entry for your entity, it will skip hitting the database and reconstruct your entity from its cache. (Mark the difference to caching an entity graph with its possibly unfetched associations and uninitialized proxies in your custom cache solution). It will also replace stale cache entries when you update an entity. It does all sorts of things related to managing the cache so that you don't have to worry about it.
Here's how can you enable Hibernate second-level cache: in addition to your configuration do the following:
In addition to the hibernate properties you already have for second-level management, namely
<entry key="hibernate.cache.region.factory_class" value="org.hibernate.cache.ehcache.EhCacheRegionFactory"/>
<entry key="hibernate.cache.provider_class" value="org.hibernate.cache.EhCacheProvider"/>
<entry key="hibernate.cache.use_second_level_cache" value="true" />
add the following entry:
<entry key="javax.persistence.sharedCache.mode" value="ENABLE_SELECTIVE" />
alternatively, you could add a shared-cache-mode configuration option to your persistence.xml (since you didn't post it, I assumed you don't use it hence the previous alternative; the following one is preferred though):
<persistence-unit name="default">
<!-- other configuration lines stripped -->
<shared-cache-mode>ENABLE_SELECTIVE</shared-cache-mode>
<!-- other configuration lines stripped -->
</persistence-unit>
Add javax.persistence.#Cacheable annotation to your #Entity classes you want to be cacheable.
If you want to add caching for collection valued associations which Hibernate doesn't cache by default, you can add a #org.hibernate.annotations.Cache annotation (with a proper cache concurrency strategy choice) for each such collection:
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(name = "product_category", joinColumns = { #JoinColumn(name = "PRODUCT_ID")
}, inverseJoinColumns = { #JoinColumn(name = "CATEGORY_ID") })
#Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
private List<Category> categories;
See Improving performance/The Second Level Cache in the Hibernate Reference Documentation for further details.
This is a nice informative article about the subject: Pitfalls of the Hibernate Second-Level / Query Caches
I have put together a small project based on your posted code snippets which you can check out to see Hibernate second-level cache in action.

The problem is that you are caching references to objects which are loaded lazily. Cache the object once it is all loaded or do not use the cache at all.
Here is how you could load the categories manually before caching it:
Item item = entityManager.find(Item.class, id);
item.getParent().getProduct().getCategories();
return item;
Also a better caching strategy would be to have the cache at the service level of your application instead of the DAO level or no cache at all.
Your issue is caused by the following events:
An Item is being retrieved without its categories then put in the cache in transaction 1. In transaction 2, you call the same method and retrieve the Item and try to read its categories. At that moment hibernate tries to read the categories from transaction 1 which is associated to the Item object but transaction 1 is already completed so it fails.

I used simple type cache with this config as below:
spring.jpa.properties.hibernate.enable_lazy_load_no_trans=true
spring.jpa.open-in-view=true
spring.cache.type=simple

MySQL or Hibernate caching issue receiving old data

I am facing one weird issue when I update the table and after a couple of seconds when I try to fetch that then I still receive the old data. When I again fetch with same query after couple of second then I receive refreshed data. Basically what I see is it takes some time to return the fresh data.
I have disabled all caching from hibernate also while fetching I am making session.clear() and marked query as uncachable.
I also look into mysql query log and I figured out that hibernate is querying to mysql, but I am receiving old data.
How can I make sure that at any given point of time I receive refreshed data only
Below is my hibernate config file
<hibernate-configuration>
<session-factory>
<property name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
<property name="show_sql">true</property>
<property name="connection.url">jdbc:mysql://127.0.0.1:4804/aluminidb?autoReconnect=true</property>
<property name="connection.username">root</property>
<property name="connection.password">root</property>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<!-- Example mapping file inclusion -->
<property name="hibernate.cache.use_second_level_cache">false</property>
<property name="hibernate.cache.use_query_cache">false</property>
<!-- Disable the second-level cache -->
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<mapping resource="com/alumini/spring/model/Alumini.hbm.xml"/>
<mapping resource="com/alumini/spring/model/Question.hbm.xml"/>
<mapping resource="com/alumini/spring/model/Events.hbm.xml"/>
</session-factory>
Below is the code to fetch the object
#Override
public Alumini login(String email, String password) {
Session session=sessionFactory.openSession();
session.clear();
Transaction t;
try{
t=session.beginTransaction();
Query query = session.getNamedQuery("chkLogIn");
query.setParameter("email",email);
query.setParameter("password",password);
query.setCacheMode(CacheMode.REFRESH);
query.setCacheable(false);
List<Alumini> aluminiList=query.list();
if(aluminiList!=null && aluminiList.size()>0){
System.out.println(aluminiList.get(0).getLastUpdated());
t.commit();
return aluminiList.get(0);
}else{
t.rollback();
return null;
}
}finally{
session.close();
}
}
So I am clearing the session, also in my config I have set all cache disabled. still when I update the record and if with in couple of seconds if I fetch the record using above method then I receive old data for once. After that it gives me latest data.

If some entities are loaded in the current Session and you run a native query, the Session might not flush automatically.
Hibernate Session offers application-level repeatable reads, so if other database transaction changes an entity, Hibernate will not refresh the current entity states.
Now, since you did not post the UPDATE part, it's hard to tell what you are doing there. The best way to address this issues is to simply log all JDBC statements as explained in this article. Then, you will know for sure whether the update was executed or not.
More, the way you do transaction and Session management is flawed as well. You don't even rollback in a finally block, and since you are using MySQL, this can lead to locks being held and causing deadlocks.
Just use a framework like Spring or Java EE to handle the Persistence Context and transaction management for you.
In your example:
Session session=sessionFactory.openSession();
session.clear();
How can one tell whether this is a new Session, and calling clear would not make any sense, or it is the same Session you used for the update?
From this code, I would assume that this is the case:
if(aluminiList!=null && aluminiList.size()>0){
System.out.println(aluminiList.get(0).getLastUpdated());
t.commit();
return aluminiList.get(0);
}else{
t.rollback();
return null;
}
But it points out that you might have skipped the Hibernate User Guide and jumped to coding Hibernate.
The aluminiList can never be null. It can only be empty.
Logging via System.out is wrong. Use a Logging framework for that.
Why do you want to commit after the query was executed? Maybe the change was not flushed at all and the query did not trigger the flush because either you set the FlushMode.MANUAL or the query is a native SQL, not a JPQL. Check out this article for more details about the difference.
You call rollback on else? What's the point? You don't trust the database that it issued the UPDATE properly and now you want to roll back that change. Or, you suspect that Hibernate did not flush, but then, why do you would you roll it back if the change didn't happen, right? But if it happened, then you should read-your-writes because that's how ACID isolation levels work.
All in all, there are many issues in the code that you posted. So, read the Hibernate User Guide and these tutorials, and you will fix all your issues. There's no other way.

hibernate doesn't issue update after flush

I'm using hibernate 3.2.7 (same problem on 3.2.5) with spring 3.0.1, all deployed on weblogic 10.3 and with an Oracle 10g database. I'm using JTA transaction management and the transaction is distributed (it is actually started and ended in another application, this code is just in between).
The configuration used by hibernate is declared in my persistence.xml and is the following:
<property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect"/>
<property name="hibernate.transaction.manager_lookup_class" value="org.hibernate.transaction.WeblogicTransactionManagerLookup"/>
<property name="hibernate.query.factory_class" value="org.hibernate.hql.classic.ClassicQueryTranslatorFactory"/>
<property name="hibernate.current_session_context_class" value="jta"/>
<property name="hibernate.connection.release_mode" value="auto"/>
The spring configuration regarding the transaction manager is the following:
<!-- Instructs Spring to perfrom declarative transaction managemenet on annotated classes -->
<tx:annotation-driven transaction-manager="txManager" proxy-target-class="true"/>
<!-- Data about transact manager and session factory -->
<bean id="txManager" class="org.springframework.transaction.jta.WebLogicJtaTransactionManager">
<property name="transactionManagerName" value="javax.transaction.TransactionManager"/>
<property name="defaultTimeout" value="${app.transaction.timeOut}"/>
</bean>
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<!-- persistence unit is missing jta data source so that application server is not
creating EntitiyManagerFactory, spring will create its own LocalContainerEntityManagerFactoryBean overriding data source-->
<property name="dataSource" ref="myDataSource"/>
<!-- specific properties like jpa provider and jpa provider properties are in persistance unit -->
<property name="persistenceUnitName" value="my.persistence.unit"/>
</bean>
<!-- define data source in application server -->
<jee:jndi-lookup id="myDataSource" jndi-name="${db.jndiName}"/>
I'm using a generic CrudDao with an update method that looks like this:
public void update(Object entity) {
//entityManager injected by #PersistenceContext
entityManager.merge(entity);
entityManager.flush();
}
public Object getById(Object id, Class entityClass) throws PersistenceException{
return (Object)entityManager.find(entityClass, id);
}
UPDATED: added the getById method.
The code that does not work as expected looks like this:
MyObject myObj = getMyObjectThroughSomeOneToManyRelation(idOne, idOther);
// till now was null
myObj.setSomeDateAttr(someDate);
genericDao.update(myObj);
MyObject myObjFromDB = genericDao.getById(myObj.getId(), MyObject.class);
The result is that if I print myObj.getSomeDateAttr() it returns me the value of someDate, if I print myObjFromDB.getSomeDateAttr() it still has null.
I've tried changing the update method to:
org.hibernate.Session s = (org.hibernate.Session) entityManager.getDelegate();
s.evict(entity);
s.update(entity);
s.flush();
And it still doesn't work.
When turning on the show_sql flag of hibernate I don't see any update occurring when doing flush nor when I query the entity manager for the object with the same id. The selects are all visible.
UPDATE:
At the end of the transaction the update is actually called and everything is written to the db. So my problem is "just" during the transaction.
I'm afraid the problem may be linked with the configuration of the transaction manager on spring and on hibernate.
Hope that someone can help me as I have already lost a day and a half with no luck.

You need to look at the hibernate merge behaviour closely. As per documentation
if there is a persistent instance with the same identifier currently
associated with the session, copy the state of the given object onto
the persistent instance
if there is no persistent instance currently associated with the session, try to load it from the database, or create a new persistent instance
the persistent instance is returned
the given instance does not become associated with the session, it
remains detached
As per your statement on the sql queries in log, it look like
MyObject myObj = getMyObjectThroughSomeOneToManyRelation(idOne, idOther); returning the persistent object but when you modify it(becomes dirty) and call merge method, new state is copied to the current persistent object in session. If you see third point merge returns persistent object which is actually new manageable persistent object which you need to use in subsequent operations.
When you call find method hibernate returns the persistent object in session and not maneagable persistent object thats why you dont find the changes in object return by find.
To fix your problem change the reurn type of update method
public Object update(Object entity) {
//entityManager injected by #PersistenceContext
return entityManager.merge(entity);
}
and in service you need to use as below
MyObject myObj = getMyObjectThroughSomeOneToManyRelation(idOne, idOther);
// till now was null
myObj.setSomeDateAttr(someDate);
//You can use myObj as well instead myNewObj
MyObject myNewObj= genericDao.update(myObj);
//No need to call get
//MyObject myObjFromDB = genericDao.getById(myObj.getId(), MyObject.class);
System.out.println("Updated value:"+myNewObj.getSomeDateAttr());
Have a look at this artical as well.

AbstractRoutingDataSource & Transactional Managers

I currently have a program which has two data sources. Each of the data source is tied to one transactional manager.
<bean id="tM" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="ds1" />
</bean>
<bean id="tM2" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="ds2" />
</bean>
If I had a function that accesses both datasource and an error occurs, if one datasource rollbacks would the second data source would also rollback?
Thanks!

If your function access datastores sequentialy (I mean it make COMMIT to the first datastore and try to COMMIT to the second one) then if error occur after first COMMIT, second data source will do ROLLBACK, but first - stay COMMITED
So, you must use one data store or JTATransactionManager.

Spring can't rollback a committed JDBC statment. This is what XADataSources and 2 phase commit are for (usually through a JTA TX manager).
You are asking for data inconsistency trying to manage this yourself because this may or may not work depending on what fails when. For example, assume this flow:
Start TX
Do work with ds1
Do work with ds2
End TX
commit ds2
commit ds1
If the commit on ds1 fails, then ds2 will stay commited. But, if the commit on ds2 fails, then the whole tx will fail and ds1 will rollback.
Also, are you sure you are always closing the DataSources in the same order they were open (first used)? Spring may take care of this, but I am not sure.

Autocommit may be on by default. Consider setting this off and managing the commits yourself .

Why do I get org.hibernate.HibernateException: No CurrentSessionContext configured

I'm writing a simple project, a business app written in Swing, using Hibernate for back-end. I come from Spring, that gave me easy ways to use hibernate and transactions. Anyway I managed to have Hibernate working. Yesterday, while writing some code to delete a bean from DB, I got this:
org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
The deletion code is simply:
Session sess = HibernateUtil.getSession();
Transaction tx = sess.beginTransaction();
try {
tx.begin();
sess.delete(ims);
} catch (Exception e) {
tx.rollback();
throw e;
}
tx.commit();
sess.flush();
and my HibernateUtil.getSession() is:
public static Session getSession() throws HibernateException {
Session sess = null;
try {
sess = sessionFactory.getCurrentSession();
} catch (org.hibernate.HibernateException he) {
sess = sessionFactory.openSession();
}
return sess;
}
additional details: I never close a hibernate session in my code, just on application closing. Is this wrong? Why do I get this on delete (only for that bean, others do work), and I don't on other operations (Insert, query, update)?
I read around and I tried to modify my getSession method simply in a sessionFactory.getCurrentSessionCall(), but I got: org.hibernate.HibernateException: No CurrentSessionContext configured!
Hibernat conf:
<hibernate-configuration>
<session-factory >
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost/joptel</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">******</property>
<property name="hibernate.connection.pool_size">1</property>
<property name="show_sql">true</property>
<property name="hibernate.hbm2ddl.auto">update</property>
..mappings..
</session-factory>
</hibernate-configuration>

I wanted to ask you one thing, why are you trying to use "OpenSession" method?
public static Session getSession() throws HibernateException {
Session sess = null;
try {
sess = sessionFactory.getCurrentSession();
} catch (org.hibernate.HibernateException he) {
sess = sessionFactory.openSession();
}
return sess;
}
You don't have to call openSession(), because getCurrentSession() method is always returns current session (Thread in case if you have configured it to be).
I got it!...
You have to specify current context in your hibernate.cfg.xml file
it should be:
<property name="hibernate.current_session_context_class">thread</property>

No CurrentSessionContext configured
Read the reference guide on Contextual Sessions. You're required to configure some provided or custom strategy for this. In a hibernate.cfg.xml, you'd configure it with
<property name="hibernate.current_session_context_class">...</property>
You'd probably want to use "thread" as the value to get per-thread sessions. When using Spring, it automatically sets this to a SpringSessionContext, allowing Spring to easily integrate Hibernate with its transaction management framework.
I come from Spring, that gave me easy ways to use hibernate and transactions.
If you're familiar with Spring, why aren't you using it to manage Hibernate here? You must already know how simple and foolproof it makes it.
I never close a hibernate session in my code, just on application closing. Is this wrong?
Yes, this is very wrong. Every session not closed is an open database connection, so your app is currently hemorrhaging connections.
Illegal attempt to associate a collection with two open sessions
That means exactly what it says. You tried to do some persistence operation (save(), update(), delete()) on something that was already associated to a different session. That's what will happen when you go randomly opening new sessions whenever, which is what's happening since SessionFactory.getCurrentSession() will always fail when no "current session context" is set. In general, never open a session just because one wasn't already there. You need to have well-defined strategies for opening and closing sessions and never let anything open a session outside of these "strategies". That's a sure path to resource leaks and errors like the one you've encountered.

I faced the same problem when I am working on a portal where I am using spring remoting with hibernate.
This kind of problem arise only if when the called service method contains multiple DAO calls that hit database with hibernate session.
And the solution is set the #Transaction annotation for those methods with multiple DAO calls. (Implies all the DOA calls with in this method should be under one transaction.)