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From "Michael McQuade" <m.mcqu...@sympatico.ca>
Subject Re:OFF TOPIC: Some pretty basic Tomcat Connection Pooling Questions????
Date Wed, 08 Sep 2004 13:41:50 GMT
Ok Yoav,  so as I understand it,   I open up my application say in the
morning,  by logging in my company......  I do not close the connection to
my database....  Now any number of users can log into it,  as they login
(servlet) I do not need to open and close my database to update it??????
this user may sit all day logged in,     you say the connection needs to be
returned to the pool????? Throughout the day, that user may access the
database at anytime.....
Im really sorry,   this is all new to me and Im trying to get a handle on it
in plain English from people who are experienced,  not all the technical
terms you get from a manual..... Im desperate for help and fast running out
of time to get it...... I have put Connection Pooling into Tomcat thru the
Server.xml and Web.xml,   per the examples from Tomcat documentation,  but
HOW  do I know it is really turned on and working????
Currently my application does a Connect and Disconnect each time a
Program/servlet is executed......  But this isnt working,  I get an 08002
(connection name in use) SqlState the second time I try to connect.....
When I remove the Connect/Disconnect from all my other servlets,   I get an
SqlState 08000 (connection exception) the first time I try to access the
database....

Please forgive me for being so stupid, Im just looking for someone that can
give me some guidance here...... If anyone from the User group would be
willing to talk in private,  so as not to disturb others in the group with
my asking for help, I would welcome that also....

Mike
m.mcquade@sympatico.ca
905-985-3438


----- Original Message ----- 
From: "Shapira, Yoav" <Yoav.Shapira@mpi.com>
To: "Tomcat Users List" <tomcat-user@jakarta.apache.org>
Sent: Wednesday, September 08, 2004 8:44 AM
Subject: RE: Some pretty basic Tomcat Connection Pooling Questions????



Hi,
You might want to get a book on good Java design practices.  The basic
ideas are there:
- Hold the connection for as little a time as possible.  That is, get it
from the pool, use it, and return it to the pool as soon as possible.
- That means you don't get the connection in a servlet init() method and
return it in a destroy() method.  That's too long a time to hold
connections usually.
- Always return connections to the pool.  Typically, this is done in the
finally clause of a try/catch block to ensure it is executed even if the
JDBC operation fails.
- You create your pool once, preferably when the app starts up, and you
close the pool itself once, preferably when the app shuts down.  A
ServletContextListener is good for this purpose.  Make sure you close
the pool.
- Servlets and other classes use the pool as needed.  You don't have to
use a one connection per servlet design (in fact those usually don't
work in the real world).

In the future, please mark non-Tomcat questions with [OFF-TOPIC] in the
subject line.  And again, consider getting a Java design practices book:
practically all of them have a chapter on JDBC connection pooling with
the above suggestions.

Yoav Shapira
Millennium Research Informatics


>-----Original Message-----
>From: Michael McQuade [mailto:m.mcquade@sympatico.ca]
>Sent: Tuesday, September 07, 2004 9:06 PM
>To: Tomcat Users List
>Subject: Some pretty basic Tomcat Connection Pooling Questions????
>
>Sorry folks,   this is a REAL Newbie to Tomcat/Java.....  Im trying to
>understand Connection Pooling as it seems I will need this in my
webapp....
>Please dont laugh too hard at me ok....
>
>When doing connection Pooling,    do you do an Open and close of your
>database for every Java class (servlet) you execute?
>
>Or
>
>Do you do a one time Open of your database at the first login?
>
>Or
>
>Do you just do an Open Database and NOT a CLOSE database for each Java
>Class (servlet)?
>
>I know this sounds stupid,   but Im currently NOT using Connection
Pooling,
>and when I  go into my first Java class (servlet),  I can OPEN/UPDATE
all
>successfully,   but when I do a Disconnect I get an SQLSTATE = 08003
>(connection does not exist)
>I then try and go into my next Java Class  (servlet) and right away,
on
>my OPEN, I get SQLSTATE = 08002 (connection name in use)
>
>It will never allow to access my database again, I have to go back to
>Application Manager,  Stop and then Start the application,   go back
into
>it,  and I get my one connection again,  but just the one.....
>
>Thanks Mike



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