-Xlog and the module system

Nicolai Parlog nipa at codefx.org
Thu Feb 2 21:27:11 UTC 2017


What the *$%& did I try then? I did that of course and thought I did not
see any messages in cases where the configuration was faulty. Under the
assumption that Xdiag's log level was too high, I went looking for a way
to set it to trace - without success.

But whatever I did that lead me to the conclusion that -Xdiag did not
print any messages was utterly wrong.

java9 -p mods/ -Xdiag:resolver -m org.codefx.demo.advent
[Resolver] Root module org.codefx.demo.advent located
[Resolver] Module java.base located, required by org.codefx.demo.advent
[Resolver] Module org.codefx.demo.advent.calendar located, required by
Error occurred during initialization of VM
java.lang.module.ResolutionException: Module
org.codefx.demo.advent.surprise not found, required by

Everything in order... Thanks for helping a noob :)

 so long ... Nicolai

On 02.02.2017 13:11, David Holmes wrote:
> On 2/02/2017 8:59 PM, Nicolai Parlog wrote:
>  Hi Alan.
>>>> The trace messages emitted by -Xdiag:resolver are printed as the
>>>> resolver runs.
> I'm sorry for being such a noob but my Google Foo failed at telling me
> how to turn trace on for -Xdiag. :( Can you help me out?
>> java -Xdiag ...
>> will enable tracing for general launcher "diagnostics" as well as the
>> resolver.
>> java -Xdiag:resolver ...
>> will only enable tracing for the resolver.
>> David
>  so long ... Nicolai
> On 02.02.2017 09:07, Alan Bateman wrote:
>>>> On 01/02/2017 21:49, Nicolai Parlog wrote:
>>>>> Hi Alan,
>>>>> `-Xdiag:resolver` is awesome! :) I think these messages are
>>>>> great candidates for info-level messages with the "modules" tag
>>>>> via unified logging.
>>>> I agree it should be transparent to developers using the JDK as to
>>>> whether the implementation is in libjvm or else where, something
>>>> that will likely more of an issue going forward when more of the
>>>> run time is written in the Java Language.
>>>>> Something else I noticed, neither Xlog nor Xdiag help with
>>>>> problematic configurations - both only start logging after
>>>>> everything checked out, so with missing modules (for example),
>>>>> they do not provide additional information.
>>>> The trace messages emitted by -Xdiag:resolver are printed as the
>>>> resolver runs. So aside from the initial module then they would see
>>>> some output when transitive dependences can't be found.
>>>> -Alan


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