Re: AS/400 JDBC Connection

[Bruce Jin <brucej@xxxxxxxxxxxxxxxxxxxx>]

Thanks Joe for pointing out the thread safety issue.

Let servlet manage a connection is only for light traffic applications 
as I mentioned. In this case one should synchronize the appropriate 
block for thread safety.



Joe Sam Shirah wrote:
>     Hi Bruce,
>
>     If I understand your response correctly, that is, using one connection
> for all instances of a servlet, you could run into some serious problems.
>
>     The primary one is that commit() and rollback() are Connection methods.
> So, even if only two users share the connection, an unexpected commit or
> rollback could occur.
>
>     The other thing I can think of off the top of my head is that while
> compliant drivers are required to handle multiple Statements on a single
> Connection, some do so by handling them sequentially, causing really bad
> response time.  I believe the JTOpen driver does it properly but you should
> always be  careful.
>
>     To Ron:  The others are correct that you should use a DataSource and
> pooling in a multithreaded context.  Some would say use them all the time.
> Normally I would point you to some articles, but I'm in a rush today.  It's
> well worth your time to google, read and understandsome articles on the
> benefits of DataSources and pooling.
>
>
>                                                          Joe Sam
>
> Joe Sam Shirah -        http://www.conceptgo.com
> conceptGO       -        Consulting/Development/Outsourcing
> Java Filter Forum:       http://www.ibm.com/developerworks/java/
> Just the JDBC FAQs: http://www.jguru.com/faq/JDBC
> Going International?    http://www.jguru.com/faq/I18N
> Que Java400?            http://www.jguru.com/faq/Java400
>
>
> ----- Original Message ----- 
> From: "Bruce Jin" <brucej@xxxxxxxxxxxxxxxxxxxx>
> To: "Java Programming on and around the iSeries / AS400"
> <java400-l@xxxxxxxxxxxx>
> Sent: Friday, March 24, 2006 10:34 AM
> Subject: Re: AS/400 JDBC Connection
>
>
>   
> > If you only have a few servlets and the traffic is not that heavy you
> > can open/close connection in your servlet. However you should open
> > connection in init method and close it in destroy method so that they
> > are done only once in the life time of the servlet. Make sure the method
> > signatures are right so that they really override the ones in super class.
> >
> > If you have many servlets and have heavy traffic it is a good idea to
> > setup a connection pool.
> >
> >
> > RPower@xxxxxxxxxx wrote:
> >     
> > > I'm trying to figure out if I should be creating and closing my
> > > connections to the JDBC each time a servlet is called or should I just
> > > open it once and leave it open?  ie:
> > >         public void performTask(HttpServletRequest req,
> > > HttpServletResponse resp) {
> > >                 sess = req.getSession(true);
> > >                 customer = (Customer) sess.getAttribute("customer");
> > >                 createAuditTrail = false;
> > >                 try {
> > >                         //!---New code put in Jun 2, 2005
> > >                         if (ds == null)
> > >                                 getDS();
> > >                         conn = ds.getConnection();
> > >                         dmd = conn.getMetaData();
> > >
> > > code here.....
> > >
> > >
> > >                 conn.close();
> > >
> > > is this efficient or am I wasting valuable resources?  Thanks,
> > >
> > > Ron Power
> > > Programmer
> > > Information Services
> > > City Of St. John's, NL
> > > P.O. Box 908
> > > St. John's, NL
> > > A1C 5M2
> > > 709-576-8132
> > > rpower@xxxxxxxxxx
> > > http://www.stjohns.ca/
> > >
> > >       
>
>