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() {} >> } >> >> > --------------------------------------------------------------------- To unsubscribe, e-mail: user-unsubscr...@struts.apache.org For additional commands, e-mail: user-h...@struts.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: user-unsubscr...@struts.apache.org For additional commands, e-mail: user-h...@struts.apache.org
