RE: RE: Event Processing at servlet startup..

Hi Jake, 
 
>>You mean besides ApplicationGateway?
Oops. That was a bit unclear.
I mean only one ApplicationGateway for the entire system.
All requests for ALL the applications are routed through it.
Exactly what a controller is supposed to do.
 
>>This is one-time setup, right? 
Correct, this a one time setup only. At the moment, Id just like to set some
static variables that 
will be used by database operations. It's read from our configuration db
table(a seed table)
which we use to map logical names to key values in foreign key tables. In
the future... I might
need to add some futher functionality to the 'startup event'
 
>> Or is it set up per/user?
I use the barracuda event hierarchy to do this. I've created listeners which
fire when a user logs in.
 
>This is one-time setup, right?  Or is it set up per/user?  If the former,
then why not use a servlet context listener?  Any setup done in
contextInitialized() is *guaranteed* by the servlet spec to be available
>before any requests are taken by servlets.  That also separates the setup
from the rest of your system so the rest of your app need not know anything
about it except that they will just assume that some >other process made the
resources available.

I'll look into creating using 'contextInitialized'.
At the moment.. we'll be using Tomcat 3.3 in production.
I hope it has this facility.
 
Regards
KD
 
 

-----Original Message-----
From: Jacob Kjome [mailto:[email protected]]
Sent: 17 June 2003 03:48
To: [email protected]
Subject: RE: [Barracuda] RE: Event Processing at servlet startup..


At 08:50 AM 6/17/2003 +0200, you wrote:



Since each developer is responsible for 1 or more applications, we rely on
the functionality I added
to ApplicationAssembler which allow's multiple processing of the assembler
xml files. 
This way... developers can work in the proverbial little black room and not
have to worry about/have to wait
for other developers. Once we deploy to test/production. The latest source
is obtained from cvs and deployed
to the correct context dir. Upon servlet startup, the application assembler
processes everyone's assembler 
files.



Just wanted to note that Barracuda1.2.0 loads multiple application assembler
files in a non-File IO way but only supports that under servlet 2.3.  So, if
you are using any modern Servlet environment, things should work for you in
the same way as it did with your previous changes, except that it will work
in a perfectly servlet-spec compatible way.

Applicable release notes are from...
http://www.barracudamvc.org/Barracuda/docs/changes.html
<http://www.barracudamvc.org/Barracuda/docs/changes.html> 
<quote>
DefaultApplicationAssembler no longer uses File IO to load configuration
files. This makes Barracuda more inline with the servlet spec which provides
no guarantee of access to the file system within a webapp. This means
Barracuda should successfully deploy directly from a .war file.
Additionally, DefaultApplicationAssembler will now load multiple assembler
files (under servlet-2.3) given a pattern to match such as '/WEB-INF/event-'
or '/WEB-INF/event*.xml'. 
</quote>

You could also have these all in a directory such as /WEB-INF/assemberfiles/
.  Just don't forget to add the trailing slash if you do that.




Now.. to get to your question.
We have only one servlet for the entire system. It's generic and know's
nothing about the system.



You mean besides ApplicationGateway?



All it's know's is to load any config files it finds and does the setting
up. 
Database pooling, and what ever it finds. 
Now. 
What I'd like to do... is to be able to set static variables based on
database information.

E.g.
<ACTUAL CODE SNIPPET HERE>
public static int STATUS_NOT_OPEN;
public static int STATUS_BUDGETING_ONLY;
public static int STATUS_BUDGETING_AND_PAYMENTS;
public static int STATUS_POSTING_ONLY;
public static int STATUS_FROZEN;
public static int STATUS_CLOSED;

public static int ACTION_INITIAL;
public static int ACTION_ADJUSTMENT;
public static int ACTION_TRANSFER;


Remember....
These variables are set based on a few database tables and their key values.
Each Application requires this sort of setup.

However, since our servlet know's nothing about any of the applications....
Up till now... I've had to hack it abit.
When the very first user log's in. I check to see if the static variables
are setup.
If not.. I load them. Each application has a Login_listener which is mapped
to the login event.

It's not Ideal as far as I'm concerned. 
That's why I'd like to have some sort of startup event fired which notifies
all applications that
they can now start processing their own initialization.
I hope that makes sense.



This is one-time setup, right?  Or is it set up per/user?  If the former,
then why not use a servlet context listener?  Any setup done in
contextInitialized() is *guaranteed* by the servlet spec to be available
before any requests are taken by servlets.  That also separates the setup
from the rest of your system so the rest of your app need not know anything
about it except that they will just assume that some other process made the
resources available.

The object respository assembler should actually be a servlet context
listener IMO.

Jake