Have anybody tried to use Hibernate in a web app the way it is described in the book?
1. Initialize SessionFactory in a HibernateUtil class static block (I'd rather initialize it in the init() method of application controller servlet and put it into the application context).
2. Open Hibernate session and store it in a static ThreadLocal variable of HibernateUtil class (I'd rather open it in a servlet filter and attach it to a request as an attribute).
3. Obtain an reference to session in Action execute() method.
4. Commit transaction and close session in servlet filter doFilter() method.

According to the author:
<quote>The job of the servlet filter is to close the Session before the response is sent to the client (and after all views are rendered and actions are executed).</guote>

I would really love to commit transaction and close session "after all views are rendered and actions are executed", if someone can confirm that it is feasible to invoke a filter after servets and JSPs.
Unfortunately I have always developed with J2EE1.2, which does not support filters. However, according to Servlet 2.3 Spec <quote>When the last filter in the chain has been invoked, the next entity accessed is the target servlet or resource at the end of the chain.</quote>.

Please can you clarify this issue? If it is not feasible to utilize filters to close session, what would be the best place to do so?

I'm surprised, because your questions are answered in the book. There is a even a filter example that closes the session after the view has been rendered, thats the whole point of the section. Maybe you should read the chapter again and have a look at CaveatEmptor source code.

If you put the Session in the request you can't access it in DAOs and have to pass it around. Works but isn't very pretty, a ThreadLocal is nicer.

Christian, thank you for your response.

I have read the chapter carefully and have seen the filter example. I have studied the CaveatEmptor source code as well.

Unfortunately, you cannot build an enterprise or web archive from the source code, and deploy and test the app on the server. I haven't even found web.xml file in the package.

I would never question the code in chapter 8, however there is one thing I don't understand. As I thought, the web container invokes all the filters first, and then passes control to the servlet, which invokes Action's execute() method and forwads the request to a JSP page, which then renders a view.

HibernateFilter should be invoked after that, however, according to the spec filters are invoked BEFORE servlets, not AFTER. Can you clarify this part for me?

"Unfortunately, you cannot build an enterprise or web archive from the source code, and deploy and test the app on the server. I haven't even found web.xml file in the package. "

This is vendor dependent. It's also what you are paid to do :)

"HibernateFilter should be invoked after that, however, according to the spec filters are invoked BEFORE servlets, not AFTER"

I wonder what is so difficult about this:



The chain.doFilter() call executes the action and renders the JSP. Please read the documentation of Servlet filters again.

This is incorrect statement. web.xml shouldn't be vendor dependent. It should be Servlet spec dependent.



There is nothing difficult about it.

The problem is, doFilter() method will NEVER be invoked AFTER servlets and JSP pages finish their work. Has this piece ever been tested?

Ok, since you will soon start to insult me its better if we stop this conversation. Go to the regular user forum and hope that somebody copy/pastes the documentation for you. CaveatEmptor does not include a presentation layer (as per README), so no web.xml. Servlet filters do not work the way you think they work. Yes, I think a few thousand people use the filters and the code from the book.

To be clear, shrek, your understanding of servlet filters is broken. You need to understand them first, before trying to argue with us.

A servlet filter is an around style interceptor, if that helps.

This is incorrect statement. web.xml shouldn't be vendor dependent. It should be Servlet spec dependent.



There is nothing difficult about it.

The problem is, doFilter() method will NEVER be invoked AFTER servlets and JSP pages finish their work. Has this piece ever been tested?

Thank you guys.

I am going to study filters thoroughly now.

I've checked the Intercepting Filter pattern (http://java.sun.com/blueprints/corej2eepatterns/Patterns/InterceptingFilter.html) in the Core J2EE Pattern Catalog.

The solution section states:


BEFORE, not AFTER.

If you look at the diagrams, you can see container invoking filters and then forwarding to the Controller (or Target). There is no filter invokation afterwards.

Please expain or post a link how is it going to work?

Sorry guys and thank you for your patience, I finally got it.