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Subject: Re: How to use it with web application?
Date: Thu, 25 Sep 2008 12:34:19 +0200
Message-ID: <0864536CC6E70F4F9FF85DE7334908CC234278@esteams1.esteam.local>
In-Reply-To: <48DB643B.9000106@tiscali.cz>
Thread-Topic: Re: How to use it with web application?
Thread-Index: Acke92bkdS0Riy5zTumnT3iEUKcpYgAAC5WQ
References: <48DB643B.9000106@tiscali.cz>
From: =?iso-8859-1?Q?Rainer_D=F6bele?= <doebele@esteam.de>
To: <empire-db-user@incubator.apache.org>

Hi David,

in a web-application you should ideally work with connection pooling, =
which is usually done by the application server (i.e. Apache-Tomcat).

We recommend the following:

1. create an Application object which is instantiated and initialized =
once when the web-application is loaded in the web application server. =
This can be done via a custom filter class registered in the web.xml =
definition file of your web-application. The application object is a =
singleton.

2. use a JNDI context to access a datasource provided by the application =
server. When initializing your application obtain a Connection from the =
data source and initialize your DB-Objects (create the driver, open the =
database, check the schema, etc.)

3. for each request, obtain a connection from the pool which you can =
then pass to the appropriate Empire-db function. When the request =
finished close the connection which will effectively return it to the =
pool.

I recommend downloading and looking at our Empire-Struts2 Example =
Application called DBWebSample provided with the distribution of the =
empire-struts2-extentions. Even if you don't intend to use Struts2 as =
your web application framework it gives a good idea on how to use =
Empire-db in a web application. You should particularly look the init() =
method of the SampleApplication class. However the sample application =
does not implement connection pooling - but it can be easily added.

Hope this is the kind of answer you expected.

Regards
Rainer

David Marko wrote:
>=20
> Hello,
> can anyone share some common scenario on how to initialise necessary
> things in web application using
> e.g. SpringFramework?
>=20
> ##### Using the code from the EmpireDB Site:
> config.init((args.length > 0 ? args[0] : "config.xml"));
> // STEP 1: Get a JDBC Connection
> Connection conn =3D getJDBCConnection();
> In step two the sample creates and initializes a database driver =
object
> for the target DBMS. This is
> HSQLDB by default.
>=20
> // STEP 2: Choose a driver
> DBDatabaseDriver driver =3D =
getDatabaseDriver(config.getDatabaseProvider());
> Then in step three the database object is opened using the driver. =
Only
> when opened, other methods
> of the database object may be used. Finally we check whether or not =
our
> database objects exist.
>=20
> // STEP 3: Open Database and check if tables exist
> db.open(driver, conn);
> databaseExists(conn);
> In order to check existence of the database the sample simply performs =
a
> query on the Departments
> table ("select count(*) from DEPARTMENTS") using the following code:
>=20
> DBCommand cmd =3D db.createCommand();
> cmd.select(db.DEPARTMENTS.count());
> db.querySingleInt(cmd.getSelect(), -1, conn);
> ###
>=20
> ... should/can be the conn and db initialised using some singleton =
pattern
> and used within the
> application in this way?
>=20
> Thanks for info,
> David