How to define qualified exports to unknown modules?

问题

I have a Maven project with two Maven modules A and B. A contains the following Java module definition:

module A {
    exports internal.util to B;
    exports external.A;
}

B contains the following Java module definition:

module B {
    requires A;

    exports external.B;
}

When I build the project, I get an error:

[WARNING] module-info.java:[16,106] module not found: B

Module B exists but because Module A is compiled before B and does not depend on it, the compiler has no way of knowing that. Because I configured the compiler to treat warnings as errors (-Werror), the build fails.

Seeing as I want to keep treating warnings as errors, what is the best way to resolve this problem?

Is there a way to hint to the compiler that this module will be declared in the future?
Is there a way to suppress all warnings of this type?

回答1:

I figured out a workaround by scanning through the JDK 11 source-code: -Xlint:-module. I am still open to a better solution if someone finds one.

UPDATE: An alternative is to use --module-source-path as demonstrated by https://stackoverflow.com/a/53717183/14731

Thank you Alan Bateman for pointing me in this direction!

回答2:

As I could infer from the question, your scenario is such that both the module A and B co-exists and the module A does not depend on the module B.

From a module system prospect, since A makes a qualified export to the module B, a warning is thrown if the module B is not resolved on the modulepath while you build A.

On IntelliJ-IDEA I could fix such an issue by adding a dependency of module B to the module A without any declaration changes. Though using the Maven framework, I couldn't imagine something without a cyclic dependency here, maybe the suggestion by khmarbaise could help.

Note: An alternate way to fix this though could also be to disable such warnings using the command-line arg :

~~-Xlint:-exports~~

Or as Alan points out for correction

-Xlint:-module

Thinking out loud, that would be since, the warning is a result of a qualified export, but about a module not found.

Useful: You could find the details over these command line args with javac command.

来源：https://stackoverflow.com/questions/53670052/how-to-define-qualified-exports-to-unknown-modules

标签

java

maven

java-module