Re: AS/400 JDBC Connection -- JAVA400-L

Thanks Joe for pointing out the thread safety issue.

Let servlet manage a connection is only for light traffic applicationsas I mentioned. In this case one should synchronize the appropriateblock 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
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----- 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/