On 05/11/10 16:50, Darren Duncan wrote:
Mike Raynham wrote:
Here, the connection information is moved from MyApp::Model::DB to
MyApp::DB, and then Catalyst::Model::Adaptor is used to glue
MyApp::Model::DB to MyApp::DB. Is it a good idea? MyApp::Model::DB
appears to be part of the Catalyst application, so if I want to access
the database from an external model, it makes sense to me to move the
connection code outside of the Catalyst application.
What you want to do is turn all the stuff that mediates access to the
database into your own shared library formatted kind of like one you
might find as a CPAN module, say "MyDBLib", and then "use" it in your
Catalyst application by way of Catalyst::Model::Adaptor.
For any configuration details that might vary either per application or
per deployment, make these user-configurable parameters of MyDBLib, with
then each of your applications would supply arguments to it when
instantiating a MyDBLib object; in the Catalyst app's case, said
arguments would be in your Catalyst app config file as is normal for
MyApp::Model::DB.
For any configuration details that are unlikely to vary per application
or per deployment, especially if they are details for which your actual
code would vary, then put these directly in your MyDBLib code instead.
Octavian Rasnita wrote:
The best idea would be to put the connection information in the
application's config file like in the example below. (This example
uses a Perl data structure, but you can use any configuration type
accepted by Config::Any).
'Model::DB' => {
schema_class => 'MyApp::Schema',
connect_info => {
dsn => 'dbi:Oracle:host=10.10.10.10;port=1521;sid=ora8',
user => 'user',
password => "password",
#name_sep => '.',
LongReadLen => 100*1024*1024,
LongTruncOk => 1,
on_connect_call => 'datetime_setup',
on_connect_do => [
"alter session set NLS_COMP='LINGUISTIC'",
"alter session set NLS_SORT='BINARY_AI'",
],
},
},
The model will access the connection information directly if it is
defined in the config file, and you can use the data from this config
file in any other external program.
You can use the module Config::JFDI for using the Catalyst config file
easier.
Now some of this looks wrong to me; a lot of those details should be in
your MyDBLib code instead of the config file. Your config file should
instead look more like this:
'Model::DB' => {
schema_class => 'MyApp::Schema',
connect_info => {
host => '10.10.10.10',
port => 1521,
user => 'user',
password => "password",
},
},
These are more details that a non-programmer user would set.
The other details should all be in your code instead, because users
shouldn't have to know and in particular if they are changed your code
could break. In particular I'm thinking of stuff like "on_connect_call"
or the fact you are using "dbi:Oracle".
Where it can get fuzzier is if your application is cross-DBMS portable,
in which case more info would need to be in the config file, but you'd
want to abstract it somehow, such as users just naming the DBMS and then
they are actually picking from a pre-defined profile which has the
code-specific details. But if the app isn't supposed to be portable, eg
if it uses Oracle-specific stuff, then don't put dbi:Oracle and NLS* and
that stuff in your user config file.
Stuff like LongReadLen might be okay here if and only if changing it
just tunes performance, like you were setting a chunk-buffer size or
something, and would have no impact on behavior nor break any code;
otherwise don't have it here.
-- Darren Duncan
Hi,
Thanks for the responses. This is all part of a fairly steep learning
curve for me. I have tried to keep things fairly simple, but I also
wanted to experiment with Moose classes...
My database connection details are very simple, consisting of just the
dsn, user and password. I have placed these, along with the
schema_class, in myapp.conf. I can access these details from both the
Catalyst app, and my external model. To help with that, I have written
two simple singleton classes using Moose:
MyApp::Config
Finds the MyApp.conf file, loads it using Config::Any, and returns it as
a hash.
MyApp::DB
Gets the application config from MyApp::Config and uses the Model::DB
parameters to connect to CHHC::Schema, and return a DBIx::Class::Schema
object.
Components in my external model can now just use MyApp::DB to obtain a
connection to the schema. I'm sure that there is plenty of room for
improvement, but so far, it works well and leaves the Catalyst app
untouched.
Regards,
Mike
_______________________________________________
List: [email protected]
Listinfo: http://lists.scsys.co.uk/cgi-bin/mailman/listinfo/catalyst
Searchable archive: http://www.mail-archive.com/[email protected]/
Dev site: http://dev.catalyst.perl.org/
