Session Management

[sripri]

This is probably an oft repeated question and yet I have a problem understanding the difference between what the documentation says vs what I am observing in my code. I have wired a hibernate DAO into spring and the code fails when I try to access an associated object lazily with a lazy initialization failed error.

I do a session.save() on the pojo (per documentation this should persist the object. However, I notice that this does not work when the invocation is from a web container. Strangely, it works when I run a junit test for the same service.

When I change the code to session.persist() it works for both variations. The only difference between save and persist per documentation is that save returns a serialized id whereas persist does not return anything. Can someone help.

[dr_pompeii]

Can you post your dao method code and test code?

[sripri]

Thanks for your response. Long weekend and I was out (reason for the delayed response). Here are the code fragments:

DAO Find method FindById:

session=sessionFactory.getCurrentSession();
Mdl1 dealer = (Mdl1) session.get("com.dao.Mdl1", id);
//session.persist(dealer);---> Makes the web app invocation work
session.save(dealer);
return dealer;

Service Method:

public Mdl1 getDealers(String companyCode, String dlrNo){
Mdl1Id id=new Mdl1Id();
id.setCompanyCode(companyCode);id.setDlrNo(dlrNo);
Mdl1 dealer=dealerDAO.findById(id);
return dealer;
}

Junit:

public void testUpdateDealers() {
Mdl1 dealer= dealerService.getDealers("15", "414050");
dealer=dealerService.mergeDealer(dealer);
List addrList=new ArrayList(dealer.getAddrs().size());
// Do some updates for example :

for(Iterator i=dealer.getAddrs().iterator();i.hasNext()
{
Addrmst addr=(Addrmst) i.next();
addr.setLastUpdatedTimestamp(new Date());
}
dealerService.updateDealer(dealer); --> JUnit works with save and persist
}

Servlet:

dealer=dealerService.getDealers(request.getParamet er("companyCode"), request.getParameter("dealerNo"));
dealerService.mergeDealer(dealer);
Set addrs=dealer.getAddrs(); ---> Does not work !

Mapping:
<set lazy="true" name="addrs" sort="natural" cascade="all" table="ADDRMST" inverse="true">
<key>
<column name="COMPANY_CODE"/>
<column name="DLR_NO"/>
</key>
<one-to-many class="com.dao.Addrmst" not-found="ignore" />
</set>

[Marten Deinum]

Please use [ code][/code ] tags when posting code.

Unit test 1 transaction (the test method), the servlet 2 transactions and 2 sessions... After each service method the transaction is committed and the session closed. Hence yuor exceptions.

[sripri]

Can you explain how you counted 2 trans. for servlets? Also, this works with persist() but not with save(). Per documentation the session behavior should be the same.

[Marten Deinum]

Persist and save are different and they work differently. Check the hibernate/jpa docs for that. Differences are subtle but they are there... Basically persist refreshes the entity, save doesn't, so after the update with persist you get a fresh instance.

I suggest a read on how spring aop and tx management works.

psuedo code (servlet).

[tx-start]
dealer=dealerService.getDealers(request.getParamet er("companyCode"), request.getParameter("dealerNo"));
[tx-end]
[tx-start]
dealerService.mergeDealer(dealer);
[tx-end]
Set addrs=dealer.getAddrs(); ---> Does not work !

psuedo code (junit)

[tx-start]
public void testUpdateDealers() {
Mdl1 dealer= dealerService.getDealers("15", "414050");
dealer=dealerService.mergeDealer(dealer);
List addrList=new ArrayList(dealer.getAddrs().size());
// Do some updates for example :

for(Iterator i=dealer.getAddrs().iterator();i.hasNext()
{
Addrmst addr=(Addrmst) i.next();
addr.setLastUpdatedTimestamp(new Date());
}	
dealerService.updateDealer(dealer); --> JUnit works with save and persist
}
[tx-end]

Do a search for open session in view, configure the filter, that way you have 1 hibernate session for the whole request, instead of multiple (for each tx).

[sripri]

Thanks for elaborating. I did check the doc btw. Not much detail. Persist per doc is "This is useful in long-running conversations with an extended Session/ persistence context." and makes a transient instance persist.

I ran a trace and got some interesting results (junit with save()) - It opens 2 sessions:

Opened new Session [org.hibernate.impl.SessionImpl@1d6747b] for Hibernate transaction
CurrentSession hash : 30831739
Triggering beforeCommit synchronization
Triggering beforeCompletion synchronization
Initiating transaction commit
Committing Hibernate transaction on Session [org.hibernate.impl.SessionImpl@1d6747b]
Triggering afterCommit synchronization
Triggering afterCompletion synchronization
Closing Hibernate Session [org.hibernate.impl.SessionImpl@1d6747b] after transaction

----> fetching lazily:

Opened new Session [org.hibernate.impl.SessionImpl@70610a] for Hibernate transaction
merging Mdl1 instance
merge successful
Triggering beforeCommit synchronization
Triggering beforeCompletion synchronization
Initiating transaction commit
Committing Hibernate transaction on Session [org.hibernate.impl.SessionImpl@70610a]
Triggering afterCommit synchronization
Triggering afterCompletion synchronization
Closing Hibernate Session [org.hibernate.impl.SessionImpl@70610a] after transaction

I notice the same for the web-app: So it is not that junit has a single transaction. Both function the same way.

[Marten Deinum]

No they don't... And again use [ code][/code ] tags when posting code/logs/xml/stacktraces

Post the full code and configuration... And remember use [ code][/code ] tags...

[sripri]

Can I just send you the project in a zip file?