Generally knowledge of success / failure will be via exception throw /
catch - you will expect certain exceptions under certain conditions and
report an appropriate error to the user.
As for tutorial, a while ago I found a book download.. apparently a
search in Google for "free practical apache struts2" will produce a
handy link.. The book seems to do an ok job all around the Struts2
landscape and introduces Spring and hibernate too.. Can't say I've
followed it word for word but I have used it for the odd tidbit of
information here and there.
Marcus
On 11/11/2010 16:20, Altenhof, David Aron wrote:
No problem, but we're starting to veer off topic here.
Of course, you'll delegate the data access to service or dao's, but ultimately
your Action is going to have to know if the transaction commit succeeded if
it's going to send an appropriate response (success/error) to the user. I'm
sure Spring must give your action access to this through some kind of injection
or AOP, but that's for another day.
BTY, does anyone have a favorite Struts2/Spring/Hibernate integration tutorial
that they've tested with a recent versions of the frameworks. I've tried a
couple with limited success.
-David
-----Original Message-----
From: Marcus Bond [mailto:mar...@marcusbond.me.uk]
Sent: Thursday, November 11, 2010 11:01 AM
To: user@struts.apache.org
Subject: Re: Interceptor attempt
Sorry to jump the thread David..
Looks like the ThreadLocal (unique per thread) session using HibernateUtil or
equivalent would be the better bet. I'd question why you need direct access to
the session from within your actions anyway as you're likely to be calling
methods on some service class to do any updating / querying anyway and to be
simply using the action class to 'control' where to go next, so it is in these
service classes that you will be trying to get hold of the session and current
transaction.
Assuming you're not requiring new transactions (equivalent of
propagation="REQUIRES_NEW" in Spring AOP) for the work that goes on in your
action then your interceptor could simply initiate a current transaction and then in a
finally block commit or rollback as required (i.e when detecting errors) before rendering
the view.
Once you're done with having a go at this then I'd say, depending upon the
complexity of your app, to let Spring do the mundane work for you - injecting
the required service beans into your Actions and declaring the transactional
stuff so your code can simply worry about the business logic and application
flow and not the intricacies of getting hold of sessions and beginning / ending
transactions etc.
Regards,
Marcus.
On 11/11/2010 14:33, Altenhof, David Aron wrote:
Greg-
Thanks for bumping my memory on when the page gets rendered. I remember reading
that somewhere, but forgot when writing this. Committing the transaction in the
action for save/delete seems to be the way to go.
Regarding ThreadLocal, I'm a bit new to Java and still struggling a bit with
the concept. You can simply simply call a
sf.getCurrentSession().beginTransaction(); to begin and
sf.getCurrentSession().getTransaction().commit(); to commit it from anywhere in
your app?
Thanks,
David
-----Original Message-----
From: Greg Lindholm [mailto:greg.lindh...@gmail.com]
Sent: Wednesday, November 10, 2010 5:15 PM
To: Struts Users Mailing List
Subject: Re: Interceptor attempt
(Sorry - premature post)
Hi David,
I've written a couple of these so let me give you some advice:
Create an Interface "HibernateAware" that your actions will implement if they
want a Hibernate Session and Transaction injected.
public interface HibernateAware
{
void setSession(Session session);
void setTransaction(Transaction tx); }
Next, you only want to create a Session and Transaction if the Action
implements HibernateAware,
Object action = invocation.getAction(); if (action instanceof
HibernateAware) {
HibernateAware ha = (HibernateAware) action;
ha.setSession(...)
ha.setTransaction(...)
...
}
else
{
return invocation.invoke();
}
Next and a bigger issue; I think it is a really bad idea to do the commit in
the interceptor. If the commit fails it is too late to tell the user or do
anything about it since your result and response has already been rendered.
You need to understand how the interceptor stack works, but the key point is
the first interceptor or action that returns a result string causes the result
to be processed and the response (jsp page) to be rendered before the
interceptor stack starts to unwind. SO if the commit fails, it's too late in
the interceptor to do anything about it, you have already rendered the
everything is OK page to the user.
What I do is to commit the transaction in the Action then if it fails I can
return a FAILURE result.
Now if you need a Transaction open in order to allow lazy loading while
rendering the jsp page what I will do is begin a second transaction.
Then in the interceptor I will Rollback the transaction and close the session
since nothing in the page rendering should modify any entities.
Next; your interceptor needs to close the session.
Your option instead of storing the session in the action is to store it and the
transaction in ThreadLocal storage. In fact if you copied your HIbernateUtil
from many of the examples it may already be storing the session in ThreadLocal
storage as this is very common.
One thing you need to be aware of regarding ThreadLocal storage and web
servers; most web servers use a thread pool for executing requests and once
your request is finished the thread gets put back into the pool for use on a
future request. This can be a problem if you don't properly clean up all
ThreadLocal storage, for example if you leave a session open and in ThreadLocal
storage when the thread gets re-used for the next request it will already have
a session in it and it will be reused. This usually happens when an exception
occurs and the session doesn't get closed so chances are the session is corrupt
or dead which will cause this later request to fail unexpectedly.
I would put the call to invocation.action() in a try block with a finally block
that closes the session and cleans up any other THreadLocal stuff you have so
it doesn't pollute the thread pool.
On Wed, Nov 10, 2010 at 4:44 PM, Greg Lindholm<greg.lindh...@gmail.com> wrote:
Hi David,
I've written a couple of these so let me give you some advice:
Create an Interface "HibernateAware" that your actions will implement
if they want a Hibernate Session and Transaction injected.
public interface HibernateAware
{
}
On Wed, Nov 10, 2010 at 3:45 PM, Altenhof, David Aron
<dalte...@iupui.edu> wrote:
Hello all, I'm trying to write my own interceptor, and have a question or two...
I'd like to write a simple interceptor that will manage hibernate sessions for
me. I know that there are more sophisticated ways to do this using Spring, etc.
but this is mainly a learning experience.
So, given the simple code below, my questions are:
1) Does it appear to be thread-safe?
2) Is there any condition, other than an unhandled exception elsewhere in
the app, that would cause the transaction not to be committed?
3) Are there any better places to stash the session and transaction
references other than the Action? I tried putting it on the value stack, but
that wreaked havoc with the Params interceptor.
Thanks!
David
public class HibernateInterceptor implements Interceptor {
public String intercept(ActionInvocation
actionInvocation) throws Exception {
Session sess =
HibernateUtil.getSession();
Transaction tx =
sess.beginTransaction();
// Put sess, tx in Action
Action action = (Action)
actionInvocation.getAction();
if(action instanceof MyAction ) {
((MyAction)action).setHibSession(sess);
((MyAction)action).setHibTransaction(tx);
}
String rslt =
actionInvocation.invoke();
try {
// Try to commit:
tx.commit();
} catch (Exception ex) {
// Try to rollback and do
other stuff here ...
}
return rslt;
}
public void destroy() {}
public void init() {} }
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