Re: DI = XML parser that can resolve references?

From:

Lew <lew@lewscanon.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sat, 20 Oct 2007 09:47:09 -0400

Message-ID:

<hPydnQIatsFDm4fanZ2dnUVZ_tOtnZ2d@comcast.com>

Olli Plough wrote:

I thought that DI was something like this:
public class MyBean
{
@PersistenceContext(name="myDB")
EntityManager em = null;
}

I have never seen an example of this annotation that uses it in collision with
an explicit initialization of the EntityManager object.

Now when I create an instance of MyBean the variable em is already
set. I don't have to bother how to get a reference to that thing and
am therefore decoupled from the respective JPA provider. How does em
get set now? Seems to me that this must be done when the lookup from
the JNDI-Server (InitialContext) is made. But then I have a dependency
on the JNDI-Server, I'm not really technology independent here.

You aren't, the program isn't as a whole, but the part where you have the
annotation is.

The annotation is a shorthand for a mess of code that allows the container to
inject the realization of the abstraction.

Maybe someone out there could help a poor one-eyed guy out with this
and explain this to me. Maybe I'm just thinking too far and thinks are
perfect the way they are ...

Neither thoughts nor things are perfect the way they are, which makes them
perfect just the way they are.

--
Lew