Type-safe DI in 299

[asookazian]

The dependency injection framework is type-safe, meaning the registry is organized around Java types, not a flat namespace, which gives more power and flexibility for component assembly.

http://www.caucho.com/resin/doc/resin-ioc.xtp

So I still don't understand what type-safe DI means exactly (referring to the italicized part above).  What is the difference between 299 DI and Seam @In, for example, in terms of type-safety? 

I just read 5.3. Typesafe resolution of 299 spec.

How about explaining the differences between these two examples:

//Weld example
@SessionScoped 
public class Login {
     @Inject Credentials credentials;
     @Inject @Users EntityManager userDatabase;
     ...
}

//Seam example
@Scope(ScopeType.SESSION)
@Name("login")
public class Login {
     @In(required=false, create=true) Credentials credentials;
     @In EntityManager entityManager;
     ...
}

The @Inject annotation defined by the Dependency Injection for Java specification identifies an injected field which is
initialized by the container when the bean is instantiated, or an initializer method which is called by the container after the
bean is instantiated, with injected parameters.

source: 1.3.1. JSF example

does not state anything about dynamic or static injection.

299 is definitely very interesting but I will say that even for a seasoned Seam developer the concepts (e.g. stereotypes) may be difficult to understand and thus learning curve involved.

[gavin.king]

So I still don't understand what type-safe DI means exactly

It means not referring to beans by string-based names that can't be validated by the compiler.

[nickarls]

I think the nice thing about 299/Weld is that you don't need to use that many annotations when you get started. I'm sure in the beginning you will get by nicely by sticking @*Scoped, @Named and @Inject on/in classes. After a while you will get a I'm sure there is a (better) way of..., then you go read the RefDoc and most probably will find it...

[asookazian]

Gavin King wrote on Nov 10, 2009 19:59:


So I still don't understand what type-safe DI means exactly

It means not referring to beans by string-based names that can't be validated by the compiler.

Ok, thx.  Good idea.  Is anybody compiling a FAQ on Weld/299?

[nickarls]

The reference docs (last updated by Dan Allen) is a good place to start, it will be in the distro or you could take it down and build it yourself from http://anonsvn.jboss.org/repos/weld/doc/trunk/reference/