Hello everyone;
I have read the Richard's osgi presentation from
http://cwiki.apache.org/FELIX/presentations.data/osgi-berlin-20070321.pdf
and there is something in the slide 36 ("OSGI R4 modularity details 4/7,
sophisticated class space consistency model")
which I don't understand clearly.
This slide is about the "uses" clause. The whole point of the slide 36
is to demonstrate that bundle* C* must not be wired to bundle *D***
(because of a potential linkage exception ...)
This is clear for me.
What is not clear is the following:
we see in the slide that:
bundle A exports package "foo"
bundle D exports package "foo"
so, in the osgi core specification, chapter 3.7, the following rules are
applied, when the framework calculates bundle resolution for bundle C:
1. A resolved exporter must be preferred over an unresolved exporter.
2. An exporter with a higher version is preferred over an
exporter with lower version.
3. An exporter with a lower bundle ID is preferred over a bundle
with higher ID.
Now:
* if A (or D) is not RESOLVED, then rules 1 applies and we are sure
that both B/C will be wired to the same exporter for package foo
(the RESOLVED exporter will win)
* if A and D are both RESOLVED, then the rules 3 applies and we are
also sure that both B/C will be wired to same exporter for package
foo (with lower bundle ID)
So, regarding the two cases above: what is the benefit of using the
"uses" clause ?
Could you please give me a use case which justify the usage of the
"uses" clause ?
Many thanks;
/pierre
