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From Craig Russell <craig.russ...@sun.com>
Subject Re: shutting down derby db in tomcat
Date Thu, 11 Nov 2004 16:56:44 GMT
Hi Henrique,

On Nov 11, 2004, at 3:33 AM, Henrique Gomes wrote:

>
> On Nov 11, 2004, at 8:00, SML wrote:
>
>> What is the 'best' way to deal with shutting down a derby db when the
>> data is used in jsp pages?  Do you shutdown when tomcat exits? What
>> happens when either the derby db or tomcat container crashes and
>> bypasses the shutdown script? Any problems, issues, corrections needed
>> on a db crash?
>
> I generally use the Destroy() method of the servlet. Look on the docs
> for the way to safely shutdown a derby database.

Part of the answer depends on whether the database is going to be used 
for more than one application. I agree, if it's bound to a single app, 
then its life cycle should be bound to the servlet's.
>
>> On a related question, is it better to open/close the db connection 
>> for
>> different queries on different jsp pages? or to keep a persistent
>> connection throughout the session?
>
> No simple answer, depends on your app.

I'd recommend in general to start out with a design that uses a 
connection pool to avoid creating a connection each time, and for each 
request, get a connection from the pool, do your work, and return the 
connection.

A nice way to isolate the issues is to define a filter for request 
processing. The init method of the filter finds or creates the 
connection pool. The doFilter method acquires a connection and adds it 
as a named attribute of the request and then calls the chained doFilter 
method. It gains control either normally or by catching an exception 
and can return the connection to the pool.

If this runs into issues, try something else, but this is the most 
scalable approach I know of.

Craig
>
>
>
Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:Craig.Russell@sun.com
P.S. A good JDO? O, Gasp!

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