Java Enum in Perl Inline Java

Question

I use Inline::Java to call a Java library from my Perl code. However, there is one function call I cannot get to work because it requires an enum type as argument.

These are my Java method signatures:

public class Initializer {
  [...]     
  public int initializeExtractor() {...}
  public int initializeExtractor(Language... languages) {...}

I am trying to call the latter version in Perl:

use Inline (
    Java => 'STUDY',

    [...]
    AUTOSTUDY => 1,
    STUDY     => [
               [...],
               'package.Language'
    ],

    JNI     => 0,
);

[...]

my $instance = package::Initializer->new( $self->directory() );
$instance->initializeExtractor($package::Language::ENGLISH);

This is the error message:

In method initializeExtractor of class package::Initializer: Can't find any signature that matches the arguments passed (package::Language=HASH(0x2328708)).
Available signatures are:
    initializeExtractor([Lpackage.Language;)
        error was: package.Language is not a kind of [Lpackage.Language; at /usr/local/lib/perl5/site_perl/5.22.4/x86_64-linux-thread-multi/Inline/Java/Object.pm line 107.

    initializeExtractor()
        error was: Wrong number of arguments at /usr/local/lib/perl5/site_perl/5.22.4/x86_64-linux-thread-multi/Inline/Java/Object.pm line 107. at /.../PP.pm line 57.

Calling the first method (initializeExtractor(), without arguments) works such fine which is why I am pretty sure my 'studies' are fine. However, according to this thread, I think I do access the Java enum in the right way.

The fact that the Java method has a varargs arguments seems not related to me, is it?

The error message seems a bit misleading because it looks like the first reported available signature matches exactly the argument that I pass.

Answer 1

The varargs argument is related to you. The declaration public int initializeExtractor(Language... languages) {...} defines a method that expects an Array of Language objects, but provides syntactic sugar so that a Java call with a single Language argument is coerced into an Array with one element, but it looks like the Inline::Java package in Perl has not been sweetened this way:

package.Language is not a kind of [Lpackage.Language;

i.e., a single package.Language argument is not the same thing as a list of package.Language objects. You can explicitly provide the list from Perl but enclosing the argument in [brackets].

$instance->initializeExtractor( [ $package::Language::ENGLISH ] );