ServiceLoader usage in automatic module fails

[Christian Stein]

> Which JAR file contains the service provider?

The service providing interface [1] is inside the api jar [2].
The service loader code resides in the Jupiter engine [3] jar and looks
like [4].

[1] org.junit.jupiter.api.extension.Extension
[2]
http://central.maven.org/maven2/org/junit/jupiter/junit-jupiter-api/5.0.0/
[3]
http://central.maven.org/maven2/org/junit/jupiter/junit-jupiter-engine/5.0.0/
[4]
https://github.com/junit-team/junit5/blob/master/junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/extension/ExtensionRegistry.java#L93


> You mentioned "restoring the class-path and provide a META-INF/services".
> Does this mean you removed the services configuration file when you
> had the JAR file on the module path as an automatic module?

No. The "demo" module is an explicit module with no service configuration.
It implements the SPI [1] and declares that in a module descriptor [5].

I wanted to write "resorting to the class-path". When I add a service
configuration file to the explicite demo module [6] at runtime and add
the location of the demo module to the class-path, the demo service
is loaded ... from the unnamed module.

[5]
https://github.com/sormuras/sawdust/blob/master/module-discoverer/demo/src/module-info.java
[6]
https://github.com/sormuras/sawdust/blob/master/module-discoverer/build.jsh#L82


On Mon, Sep 11, 2017 at 12:52 PM, Alan Bateman <Alan.Bateman at oracle.com>
wrote:

>
>
> On 11/09/2017 11:03, Christian Stein wrote:
>
>> Hi jigsaw team,
>>
>> I discovered an issue with the ServiceLoader trying to load services on
>> the
>> module-path, when the actual ServiceLoader.load() call resides in an
>> automatic module.
>>
>> I compiled a small demo at [1] and it's console output is visible at [2].
>> If you want to re-run the demo, just call "jshell build.jsh" in the root
>> directory.
>>
>> In summary, you have to elevate the automatic module to an explicit one,
>> via adding a module-info.class, to get the ServiceLoader load the service
>> on the module-path. This can be done with pro's [3] "modulefixer" plugin.
>>
>> When resorting the class-path and provide a "META-INF/services" file and
>> also add the module to the class-path, I can get service loaded ... but
>> only within the unnamed module.
>>
> Which JAR file contains the service provider? You mentioned "restoring the
> class-path and provide a META-INF/services". Does this mean you removed the
> services configuration file when you had the JAR file on the module path as
> an automatic module?
>
> -Alan
>