Create a ConnectionAcquisitionMode as corollary to ConnectionReleaseMode
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Key: HHH-5184
URL:
http://opensource.atlassian.com/projects/hibernate/browse/HHH-5184
Project: Hibernate Core
Issue Type: Improvement
Reporter: Steve Ebersole
Fix For: 3.6
Originally ConnectionReleaseMode was added to work around a particular problem of
connection "leaking" by JTA containers when used in situations of nested session
EJB calls. The connection was not really leaked, but it would appear that way to the JTA
resource tracker.
The situation was:
{code}
class EJB1 {
public void doSomething() {
Session s = getCurrentSession();
...
ejb2.doSomethingElse();
// now use the HIbernate session
}
}
class EJB2 {
public void doSomethingElse() {
Session s = getCurrentSession();
// Use the session in a way that requires a Connection...
}
}
{code}
What happens is that EJB1 obtains a Session reference. Just getting a Hibernate Session
does not make it get a Connection; the Session delays getting a Connection until it
actually needs one. EJB1 then makes the call into EJB2. Again, EJB2 obtains the same
Session reference and does some work, so the Session obtains a Connection. Historically
that Connection would be held until the Session closed. However that was problematic in
this scenario above; to the JTA container it looks like EJB2.doSomethingElse() is leaking
the connection outside the transaction boundary (this was many years ago and AFAIU many of
these JTA scoping routines have become more sophisticated).
At the time we decided to add the idea of Connection "releasing". However
constantly releasing and re-obtaining the Connection can affect performance. Another
solution to the problem above is to obtain the Connection up front instead.
So initially I see:
ConnectionAcquisitionMode.AS_NEEDED
ConnectionAcquisitionMode.IMMEDIATELY
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