Re: [Hibernate-devel] mvc & lazy loading

[Jon L. <jon...@xe...>]

Brad,

This is exactly what I do...  I also have a couple different versions of my
filter that handler their own URL filtering using the Apache ORO library.  I
do this so I can more complex regular expressions for the the URL
matching...

Jon...
----- Original Message -----
From: "Brad Clow" <bra...@wo...>
To: <hib...@li...>
Sent: Saturday, August 31, 2002 7:38 AM
Subject: Re: [Hibernate-devel] mvc & lazy loading


> jon,
>
> this seems like a pretty neat way of doing it.  do u use <filter-mapping>
> elements in the web.xml to control which requests it gets applied to - so
u
> only have a session created for requests that actually need one?
>
> brad
>
>
> ----- Original Message -----
> From: "Jon Lipsky" <jon...@xe...>
> To: "Christoph Sturm" <ch...@mc...>; "Brad Clow"
> <bra...@wo...>; <hib...@li...>
> Sent: Tuesday, August 27, 2002 7:46 PM
> Subject: Re: [Hibernate-devel] mvc & lazy loading
>
>
> > Hi All,
> >
> > I use a Filter (a new addition in the 2.3 servlet spec) to open and
close
> my
> > Hibernate sessions.  By doing it this way it doesn't matter if I am
using
> > Velocity or JSP or something else to access Hibernate.  As far as the
> "view"
> > is concerned the Hibernate session just exists, and only the Filter has
to
> > worry about opening and closing it.
> >
> > I was looking at the examples inclued with Hibernate and I was thinking
> that
> > maybe an example should be added of using a Filter since it's a good way
> to
> > cleanly seperate the creation and closing of the sessions for a web
> > application.
> >
> > Jon...
> >
> > PS - Here is a code snippet to get you started if you want to do it this
> > way:
> >
> > package example;
> >
> > import cirrus.hibernate.Datastore;
> > import cirrus.hibernate.Session;
> > import cirrus.hibernate.SessionFactory;
> > import cirrus.hibernate.Hibernate;
> >
> > import javax.servlet.*;
> > import javax.servlet.http.HttpServletRequest;
> > import java.io.IOException;
> >
> > public class HibernateFilter implements Filter
> > {
> >  static org.apache.log4j.Category log =
> > org.apache.log4j.Category.getInstance(HibernateFilter.class.getName());
> >
> >  private Datastore datastore;
> >  private SessionFactory sessions;
> >
> >  public void doFilter(ServletRequest request, ServletResponse response,
> > FilterChain chain) throws IOException, ServletException
> >  {
> >   try
> >   {
> >    // Get the http session id from the request, then we will try to get
> the
> > Hiberate
> >    // Session from the request.  If it doesn't exist, then we will
create
> > it, otherwise
> >    // we will use the one that already exists.
> >    String vSessionId =
> > ((HttpServletRequest)request).getSession(true).getId();
> >    Session vSession = (Session)request.getAttribute(vSessionId);
> >
> >    if (vSession == null)
> >    {
> >     vSession = sessions.openSession();
> >     request.setAttribute(vSessionId, vSession);
> >
> >     if (log.isDebugEnabled())
> >     {
> >      log.debug("Opened hibernate session.");
> >     }
> >    }
> >   }
> >   catch (Exception exc)
> >   {
> >    log.error("Error opening Hibernate session.", exc);
> >   }
> >
> >   try
> >   {
> >    chain.doFilter(request, response);
> >   }
> >   finally
> >   {
> >    try
> >    {
> >     String vSessionId =
> ((HttpServletRequest)request).getSession().getId();
> >     Session vSession = (Session)request.getAttribute(vSessionId);
> >
> >     // Only try to close the connection if it is open, since it might
have
> > been
> >     // closed somewhere else by mistake.
> >     if (vSession.isOpen())
> >     {
> >      vSession.close();
> >
> >      if (log.isDebugEnabled())
> >      {
> >       log.debug("Closed hibernate session.");
> >      }
> >     }
> >    }
> >    catch (Exception exc)
> >    {
> >     log.error("Error closing Hibernate session.", exc);
> >    }
> >   }
> >  }
> >
> >  public void init(FilterConfig aConfig) throws ServletException
> >  {
> >   // Initialize your datastore
> >   datastore = Hibernate.createDatastore();
> >
> >   // Initialize your the object -> db mappings
> >   // ...
> >
> >   // Initialize your session
> >   sessions = datastore.buildSessionFactory();
> >  }
> >
> >  public void destroy()
> >  {
> >
> >  }
> > }
> >
> >
> >
> > ----- Original Message -----
> > From: "Christoph Sturm" <ch...@mc...>
> > To: "Brad Clow" <bra...@wo...>;
> > <hib...@li...>
> > Sent: Tuesday, August 27, 2002 10:47 AM
> > Subject: Re: [Hibernate-devel] mvc & lazy loading
> >
> >
> > > Hi Brad!
> > >
> > > This subject is an interesting one that I was also thinking of lately.
> > > I did a test app with maverick (mav.sourceforge.net), and there it was
> > > really easy. If the controller(=model) implements ModelLifetime, a
> discard
> > > function is called when the views are finished and the model is
> discarded.
> > > There I closed my session. Other frameworks that just forward to the
> view
> > > dont offer this functionality.
> > > For most of my stuff I use webwork, so I'd like a solution that works
> > there
> > > too. I was thinking of closing the session in the finalize method of
my
> > > controller, but then I dont really know when the session will be
closed.
> > > Another possibility would be to to pass the session to velocity, and
> close
> > > it in the velocity view servlet after all is rendered.
> > >
> > > How did you implement it?
> > >
> > > regards
> > >  chris
> > > ----- Original Message -----
> > > From: "Brad Clow" <bra...@wo...>
> > > To: <hib...@li...>
> > > Sent: Tuesday, August 27, 2002 12:38 AM
> > > Subject: [Hibernate-devel] mvc & lazy loading
> > >
> > >
> > > >
> > > > to date, we have avoided using lazy loading when writing a web app
in
> > > > one of the standard mvc type frameworks (eg. struts, webwork, etc).
> > > > this is because objects r typically retrieved, placed in the request
> > > > attributes, session closed and control is then passed to the view
> (JSP,
> > > > velocity, etc).  if the view attempts to access a lazy loaded
> collection
> > > > in one of the objects an exception is thrown as the associated
session
> > > > is closed.
> > > >
> > > > what do other people do?
> > > >
> > > > yesterday, i spent a few hours writing a very simple webapp
framework
> > > > that uses velocity for the view.  it enables the velocity rendering
to
> > > > be done while a session is open.  so far this is working quite well
> for
> > > > us.
> > > >
> > > > comments?
> > > >
> > > > brad
> > > >
> > > > > _______________________________
> > > > > brad clow
> > > > > chief technical officer
> > > > > workingmouse
> > > > >
> > > > > email: bra...@wo...
> > > > > web:   http://www.workingmouse.com
> > > > >
> > > >
> > > >
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