<see below>
>From: "Craig R. McClanahan" <[EMAIL PROTECTED]>
>Isn't that basically option 2?
>
>The only disadvantage is that, unless you're careful, your DataAdaptor
>class will be dependent on Struts unless you make it have a static
>setDataSource() method or something. But you're still tying your business
>logic classes to the presence of DataAdaptor in every program that uses
>this approach (which may or may not be a big deal).
>
> > Craig.
>
Number 2 was:
* Static methods ... Most DB connection pool implementations offer a way
to retrieve a DataSource or Connection via a static method. Advantage:
no handing around extra method parameters. Disadvantage: ties you to
that connection pool's APIs.
I read this as I should use the static methods provided by the specific
connection pool. What I meant was, I would create a generic
DataAdaptorFactory class and a DataAdaptor interface which could be be
configured off of a properties file to determine which data adaptor to use.
This way I can abstract myself from implementation details.
I don't think my business layer would even know about the DataAdaptor, they
would be communicating with my Data layer objects, which would take care of
data issues.
Something like:
public interface DataAdaptor {
public java.sql.Connection getConnection();
}
public class DataAdaptorFactory {
public static DataAdaptor getDataAdaptor() {
//lookup data adaptor implementation class
//in DataAdaptor.properties file
//do a class for name on that implemenation class
//return that class.
}
}
DataAdaptor.properties:
dataAdaptor=mypackage.MySqlDataAdaptor
public class MySqlDataAdaptor implements DataAdaptor {
public java.sql.Connection getConnection() {
//mysql specific stuff to get a connection
}
}
public class EmployeeDataObject {
public EmployeeList retrieve(String fields, String filters) {
DataAdaptor data = DataAdaptorFactory.getDataAdaptor();
Connection conn = data.getConnection();
//execute a query based on the fields and filters passed in
//transform the results to an 'EmployeeList' collection
}
}
Craig.
>Craig
>
> >
> > >From: "Craig R. McClanahan" <[EMAIL PROTECTED]>
> > >Reply-To: "Struts Users Mailing List" <[EMAIL PROTECTED]>
> > >To: Struts Users Mailing List <[EMAIL PROTECTED]>
> > >Subject: Re: Alternative Datsource Hot-potatoing...
> > >Date: Fri, 6 Sep 2002 11:40:48 -0700 (PDT)
> > >
> > >
> > >
> > >On Fri, 6 Sep 2002, Craig Tataryn wrote:
> > >
> > > > Date: Fri, 06 Sep 2002 12:41:26 -0500
> > > > From: Craig Tataryn <[EMAIL PROTECTED]>
> > > > Reply-To: Struts Users Mailing List <[EMAIL PROTECTED]>
> > > > To: [EMAIL PROTECTED]
> > > > Subject: Alternative Datsource Hot-potatoing...
> > > >
> > > > I was wondering if someone could give me a heads up on some
>alternative
> > > > means for which to give my data access layer access to my
>datasource.
> > > >
> > > > I don't really like the idea of my controller grabbing the
>Datasource,
> > > > passing it off to my business layer, who in turn passes it along to
>my
> > >data
> > > > layer. I guess I'm sort of a purest, but I don't think the Business
> > >layer
> > > > should know anything about the database, and that means it shouldn't
> > >even
> > > > have methods that take connections or datasourses as parameters.
> > > >
> > > > I think the only thing I like about the Controller passing along a
> > > > connection to my business/data layer is the fact that I can first
>open a
> > > > transaction before passing the connection along, and then I can
>commit
> > >the
> > > > transaction when everything is done. Thus my transactions are at
>the
> > > > controller level, and can be managed there.
> > > >
> > > > Back in my old VB/COM days, we had a sort of DB Utilities class
>which
> > >could
> > > > be accessed from the datalayer. You would ask it to give you a
> > >connection,
> > > > and it would get it for you. Should I make my own class for
>datasource
> > > > access which is intitalized upon application start with the
>Datasource
> > > > object found by struts? Then the rest of my datalayer can simply
>use
> > >it?
> > > >
> > >
> > >Three basic options exist:
> > >
> > >* Hand a DataSource (I normally prefer to send a Connection instead,
>but
> > > either works) to your business logic method as a parameter to each
>call
> > > that needs it. Advantage: no binding to anything. Disadvantage:
>can
> > > be a pain to hand it around.
> > >
> > >* Static methods ... Most DB connection pool implementations offer a
>way
> > > to retrieve a DataSource or Connection via a static method.
>Advantage:
> > > no handing around extra method parameters. Disadvantage: ties you
>to
> > > that connection pool's APIs.
> > >
> > >* JNDI resources -- All J2EE app servers (and some servlet containers
>like
> > > Tomcat 4) offer support for JNDI resources that are accessible to
>your
> > > business logic directly like this:
> > >
> > > import javax.naming.Context;
> > > import javax.naming.InitialContext;
> > >
> > > InitialContext ic = new InitialContext();
> > > Context ctx = (Context) ic.lookup("java:comp/env");
> > > DataSource ds = (DataSource) ctx.lookup("jdbc/EmployeeDb");
> > >
> > > where "jdbc/EmployeeDb" is a resource reference you have declared in
> > > your web.xml file. Advantage: No parameter passing, no connection
> > > pool API lock-in. Advantage: configuration of the data source is
> > > external to your webapp (it's done with the server configuration
> > > capabilities). Disadvantage: container must support this.
> > >
> > >For info on how to use the third option in Tomcat, see:
> > >
> > >
> >
> >http://jakarata.apache.org/tomcat/tomcat-4.1-doc/jndi-resources-howto.html
> > >
> > >(NOTE -- if you're going to use Tomcat, definitely go for 4.1; 4.0's
> > >support has problems for many users).
> > >
> > > > Thanks,
> > > >
> > > > Craig.
> > > >
> > > > Craig W. Tataryn
> > > > Programmer/Analyst
> > > > Compuware
> > >
> > >Craig
> > >
> > >
> > >--
> > >To unsubscribe, e-mail:
> > ><mailto:[EMAIL PROTECTED]>
> > >For additional commands, e-mail:
> > ><mailto:[EMAIL PROTECTED]>
> >
> >
> > Craig W. Tataryn
> > Programmer/Analyst
> > Compuware
> >
> > _________________________________________________________________
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> >
>
>
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Craig W. Tataryn
Programmer/Analyst
Compuware
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