Thanks for pointing that out. I usually use JTA-enabled datasources so I
don't muck around with UserTransaction directly that much.
Derek
On Wed, Sep 10, 2008 at 2:23 PM, Martin Ellis <[EMAIL PROTECTED]> wrote:
>
> On Wed, Sep 10, 2008 at 4:27 PM, Kris Nuttycombe
> <[EMAIL PROTECTED]> wrote:
> > The only question I have is thread safety - it doesn't seem
> > like I should really be using a variable on the singleton to store the
> > transaction; should I instead be creating a separate RequestVar to
> > hold it?
>
> It is thread safe to use a singleton - in fact, it's what Sun do in
> the code that accompanies the Java EE Tutorial...
>
> web/books/src/main/java/com/sun/books/listeners/ContextListener.java:
>
> public final class ContextListener implements ServletContextListener {
> @PersistenceUnit
> private EntityManagerFactory emf;
> private ServletContext context = null;
> @Resource
> private UserTransaction utx;
>
> public void contextInitialized(ServletContextEvent event) {
> context = event.getServletContext();
>
> try {
> context.setAttribute("emf", emf);
> Globals.UTX = utx;
>
>
> ... where Globals is defined as:
>
> public class Globals {
> public static UserTransaction UTX;
> }
>
>
> Hence, using val instead of def should be fine.
>
> The begin() and commit() javadoc on UserTransaction:
> "Create a new transaction and associate it with the current thread."
> "Complete the transaction associated with the current thread. When
> this method completes, the thread is no longer associated with a
> transaction."
>
> The transaction is associated with the thread that called begin()
> 'internally', so there's no need to associate it with a thread
> manually.
>
> See also:
> http://java.sun.com/javaee/5/docs/tutorial/doc/bnafo.html
>
> Martin
>
> >
>
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