Add a custom JMOD to the module path with Java 9

问题:

I created a simple JMOD file with the jmod tool like this

$JAVA_HOME/bin/jmod create --class-path classes test/samples.jmod

Next, I tried to execute a class within that module by running:

java -mp test -m de.mypackage/de.mypackage.Test

Which resulted in the following exception:

Error occurred during initialization of VM
java.lang.module.ResolutionException: JMOD files not supported: test/samples.jmod
  at java.lang.module.Resolver.findWithBeforeFinder(java.base@9-ea/Resolver.java:729)
  at java.lang.module.Resolver.resolveRequires(java.base@9-ea/Resolver.java:86)
  at java.lang.module.Configuration.resolveRequiresAndUses(java.base@9-ea/Configuration.java:370)
  at java.lang.module.ModuleDescriptor$1.resolveRequiresAndUses(java.base@9-ea/ModuleDescriptor.java:1986)
  at jdk.internal.module.ModuleBootstrap.boot(java.base@9-ea/ModuleBootstrap.java:263)
  at java.lang.System.initPhase2(java.base@9-ea/System.java:1928)

If I just set my classes directory (that I used to create the JMOD file) as modulepath, everything is working as expected.

Is it generally not possible to have JMOD files on the modulepath? And if this is the case, is there any reason for that?

回答1:

See http://openjdk.java.net/jeps/261#Packaging:-JMOD-files

JMOD files can be used at compile time and link time, but not at run time. To support them at run time would require, in general, that we be prepared to extract and link native-code libraries on-the-fly. This is feasible on most platforms, though it can be very tricky, and we have not seen many use cases that require this capability, so for simplicity we have chosen to limit the utility of JMOD files in this release.