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OSGi: about import [message #28427]

Sun, 13 July 2003 14:15

Eclipse User

Originally posted by: pascal_rapicault.yahoo.fr

Hello,

I have the question about imports.

Here is the test case:
Bundle A: Class A
Bundle B: Class B extends A

Bundle C: uses class B

The obvious imports are:
Bundle A: export A
Bundle B: import A, export B

Bundle C: import B,
does it also need to import A (because B extends A and A is required
to verify B)

Thanks,

PaScaL

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Re: about import [message #28503 is a reply to message #28427]

Tue, 15 July 2003 07:27

Vasil Panushev

Messages: 14
Registered: July 2009

Junior Member

Hi

> Bundle C: import B,
> does it also need to import A (because B extends A and A is
required to verify B)

yes and no
"no" is because the classloader ot Bundle B takes care for loading class A
and bundle B imports the package of class A.
In OSGi every bundle is responsible for resolving its own classes. As an
example - class B may use some classes from bundle D - in this case bundle C
will NOT have to import the packages of D too.

"yes" is because of a little flaw in all JDK compilers prior to 1.4 (well,
maybe it is not a flaw but in this situation it is an obstacle )
in the following situation:
class A has mehtod foo()
class B which extedns A does NOT override foo()
class C calls B.foo()

all JDK compilers prior to 1.4 place in the bytecode of C a direct reference
to A (so the method call is in fact A.foo()).
In this case the classloader of class C will try to load class A and this
will fail unless bundle C imports the package of class A.

best regards
Vasil

"Pascal Rapicault" <pascal_rapicault@yahoo.fr> wrote in message
news:berphh$t3p$1@eclipse.org...
> Hello,
>
> I have the question about imports.
>
> Here is the test case:
> Bundle A: Class A
> Bundle B: Class B extends A
>
> Bundle C: uses class B
>
> The obvious imports are:
> Bundle A: export A
> Bundle B: import A, export B
>
> Bundle C: import B,
> does it also need to import A (because B extends A and A is
required
> to verify B)
>
> Thanks,
>
> PaScaL
>
>
>
>
>

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Re: OSGi: about import [message #29332 is a reply to message #28427]

Thu, 17 July 2003 20:36

Eclipse User

Originally posted by: Peter.Kriens.aQute.se

C does not have to import A because it only refers to B. When class B is
loaded, it will come from Bundle B which has visibility of A and can load A.

It would be VERY bad practice if you were forced to know the
implementation dependencies of packages you used ...

Hope this helps, kind regards,

Peter Kriens

Pascal Rapicault wrote:

> Hello,
>
> I have the question about imports.
>
> Here is the test case:
> Bundle A: Class A
> Bundle B: Class B extends A
>
> Bundle C: uses class B
>
> The obvious imports are:
> Bundle A: export A
> Bundle B: import A, export B
>
> Bundle C: import B,
> does it also need to import A (because B extends A and A is required
> to verify B)
>
> Thanks,
>
> PaScaL
>
>
>
>
>
>

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