Question regarding the "Modular platform"

Volker Simonis volker.simonis at
Wed Feb 22 18:04:26 UTC 2017


referring to the "Java SE 9 (JSR 379) Early Draft Review
Specification" I'd like to get some clarifications regarding the
definition of the "Modular platform" and its implications on
implementors of Java SE 9.

Section "7 Modular platform" of the specification starts with the
statement that it "..uses the Java Platform Module System, specified
by JSR 376, to modularize the Java SE Platform". One of the goals is
to "Divide the Java SE Platform into a set of modules that can be
combined at compile time, build time, or run time into a variety of
configurations including, but not limited to..Custom configurations
which contain only a specified set of modules and the modules
transitively required by those modules."

What is "compile time, build time, or run time" referring to? Is it
the "compile time / build time" of the platform itself? I.e. should it
be possible for an implementor to only build and assemble a subset of
the standard modules into his "Java SE Platform"? And will this still
be called "Java SE 9"?

Later on, in the "Conformance" section, the specifications mentions
that "Every Implementor of this Specification must implement the
java.base module. Every Implementor may, further, implement a set of
one or more additional standard SE modules so long as that set is
closed, i.e., contains every standard module required by any member of
the set.".

>From this and the previous statement I would expect that an
independent implementor as well as an OpenJDK distributor could build
a "Platform implementation'" which only contains the java.base module,
certify that with the Java SE 9 TCK (because "The Technology
Compatibility Kit (TCK) for this Specification will be structured to
allow testing of arbitrary configurations of SE modules present in a
Platform Implementation.") and provide that to its customers. Is that

And if it is correct, how could a user of such a "Platform
implementation" distinguish two different implementations which
provide a different subset of standard modules? Currently, as far as I
can see in the RI, running "java -v" always identifies itself as
"Java(TM) SE Runtime Environment (build 9-ea+xxx)", no difference
which modules it contains. The user would have to run  "jimage list"
on the modules file to find out which modules are included (not to
mention that "jimage" isn't a standard tool anyway).

That said, the "Goals" section also mentions that "standard modules
that are part of the Java SE Platform Specification, and thereby
mandatory in every Platform Implementation" which seems to contradict
with the above points which explicitly allow sub-setting (as long as
that set is closed).

Finally, it would be good to have a new version of the "OpenJDK
Community TCK License Agreement" (OCTLA) available BEFORE the final
vote on JSR 379. I understand that standardization and licensing are
two different things. But first, JSR 379 explicitly references the TCK
and second voting on a new standard which technically allows
sub-setting and modularization is pointless if these new possibilities
would be prohibited by licensing. At least the current OCTLA [1]
explicitely states that a "Compatible Licensee Implementation" has to
"..fully implements the Java Specification, including all its required
interfaces and functionality..".

Thank you and best regards,


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