Hi Eric,
currently OJB isn't a singleton (was a singleton before 0.9.4).
OJB.getInstance returns a new Implementation instance
on each call. So get the references to Implementation
and Database from ContextIntializer (or a class
encapsulate this stuff) instead of
doing
OJB.getInstance();
in your action class
> Where and when should I be opening and closing the database. I assumed
I
> would only have to open it once on application startup and close it on
> shutdown.
yes
> Is this assumption incorrect? If so what are the performance
> consequences of opening and closing the Database object?
open/close database isn't a big performance impact
regards,
Armin
----- Original Message -----
From: "Eric Northam" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, June 13, 2003 4:41 PM
Subject: Database Lifecycle
> I'm using OJB in Tomcat and I couldn't seem to locate any information
about
> where and when to open and close the Database object. I assumed that
> OJB.getInstance would return a reference to a singleton object so that
if I
> created a new database in one place that would be sufficient. I wrote
a
> ContextIntializer which is a class that has a contextInitialized
method that
> gets called on webapp deployment and put the following code in it:
>
> -----
> Implementation odmg = OJB.getInstance();
>
> database = odmg.newDatabase();
>
> try {
>
> database.open(null, Database.OPEN_READ_WRITE);
>
> }
>
> catch (ODMGException e) {
>
> log.fatal("Error initializing the database", e);
>
> throw new InitializationException("Error initializing the database",
e);
>
> }
>
> ------
>
> I then put then put the following code in a Struts action:
>
> -----
>
> Implementation odmg = OJB.getInstance();
>
> Transaction tx = odmg.newTransaction();
>
> -----
>
> I know that the datbase is opened because of the log messages I print
out,
> but later when the action is called I get:
>
> org.odmg.DatabaseClosedException: Database is NULL, must have a DB in
order
> to create a transaction
>
>
>
> Where and when should I be opening and closing the database. I assumed
I
> would only have to open it once on application startup and close it on
> shutdown. Is this assumption incorrect? If so what are the performance
> consequences of opening and closing the Database object?
>
> Eric
>
>
>
>
>
>
>
>
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