Case - class from required module is not available

[Mandy Chung]

This is an interesting scenario - module c is linked with module b only 
whereas module d is linked with module a only.

$ jmod -L mlib dump-config c
configuration roots = [c at 1.0]
   context +c
     module c at 1.0
       view c at 1.0
     local (1)
       c.C:c at 1.0
     remote (46)
       b=+b
   context +b
     module b at 1.0
       view b at 1.0
     local (1)
       b.B:b at 1.0
     remote (45)
   ....

$ jmod -L mlib dump-config d
configuration roots = [d at 1.0]
   context +d
     module d at 1.0
       view d at 1.0
     local (1)
       d.D:d at 1.0
     remote (45)
   context +a
     module a at 1.0
       view a at 1.0
     remote (45)
   ....

module c requires module b and an optional dependence on module c. 
module b has an optional dependence on module a@<1.0 which does not 
exist.   Thus module c is not linked with module a at 1.0 as it doesn't 
satisfy the dependence constraint.

module d has an optional dependence on both module a and b with no 
version specified.  The resolver attempts to resolve module d with 
module a at 1.0 and b at 1.0.   Since there is no module satisfying the 
dependence from module d *and* from module b on a - i.e. "requires 
optional a" and "requires optional a@<1.0", module a at 1.0 is not resolved 
and linked in module d's configuration.

Mandy

On 3/27/2012 7:24 AM, Alexey Fedorov wrote:
> Hello!
>
> Suppose we have simple construction with 4 modules:
>
> ****************************************
>
> module a @ 1.0 {
> }
>
> ****************************************
>
> module b @ 1.0 {
>     requires optional a@<1.0;
>     exports b;
> }
>
> package b;
> public class B {
> }
>
> ****************************************
>
> module c @ 1.0 {
>     requires optional a;
>     requires b;
>
>     exports c;
>     class c.C;
> }
>
> package c;
> public class C {
>     public static void main(String[] args) {
>         try {
>             Class bClazz = Class.forName("b.B");
>             System.out.println(bClazz + " is AVAILABLE from c.C!");
>         } catch (ClassNotFoundException e) {
>             System.out.println("b.B is NOT AVAILABLE from c.C!");
>         }
>     }
> }
>
> ****************************************
>
> module d @ 1.0 {
>     requires optional a;
>     requires optional b;
>
>     exports d;
>     class d.D;
> }
>
> package d;
> public class D {
>     public static void main(String[] args) {
>         try {
>             Class bClazz = Class.forName("b.B");
>             System.out.println(bClazz + " is AVAILABLE from d.D!");
>         } catch (ClassNotFoundException e) {
>             System.out.println("b.B is NOT AVAILABLE from d.D!");
>         }
>     }
> }
>
> ****************************************
>
> Running c.C and d.D in sequence shows:
>
>> class b.B is AVAILABLE from c.C!
>> class b.B is NOT AVAILABLE from d.D!
>
> and it seems very strange for me. Could you please clarify, why class 
> b.B is not available from d.D?
>
> -- 
> Alexey
>
>