How can I call Perl from Java?

Question

I have a Perl module that I would like to use from Java. Is there a way to call this code using either ActiveState Perl on Windows or the generic Perl that comes with Linux? I have found references to JPL but it doesn’t appear to be maintained anymore.

Answer 1

Inline-Java is the usual library to call java from Perl, and this post propose a org.perl.java module which should allow calling Perl from Java, as asked.

However, because of the unpredictability of the JNI implementations for different JVMs it is difficult to say what combinations of JVM and Perl will work. Typically, what is required is Perl with MULTIPLICITY, and threads compiled in. That means he uses a custom built Perl.

Otherwise, Inline::Java::Callback allows you to call Perl functions from Java. To do this you need to create an org.perl.inline.java.InlinePerlCaller object. Here is a example of a typical use:

use Inline Java => <<END ;
import java.util.* ;
import org.perl.inline.java.* ;

class Pod_regexp extends InlineJavaPerlCaller {
    public Pod_regexp() throws InlineJavaException {
    }

    public boolean match(String target, String pattern)
        throws InlineJavaException {
        try {
            String m = (String)CallPerlSub("main::regexp",
            new Object [] {target, pattern}) ;

            if (m.equals("1")){
            return true ;
        }
    }
    catch (InlineJavaPerlException pe){
        // $@ is in pe.GetObject()
    }

    return false ;
    }
}
END

my $re = new Pod_regexp() ;
my $match = $re->match("Inline::Java", "^Inline") ;
print($match . "n") ; # prints 1

sub regexp {
    my $target = shift ;
    my $pattern = shift ;

    return ($target =~ /$pattern/) ;
} 

Answer 2

Is this not what Runtime.exec() is for?

Runtime.getRuntime().exec("/usr/bin/perl myPerl.pl");

Or am I misunderstanding the question?

Answer 3

Rakudo allows you to run Perl6 inside a JVM, and there is a Perl5 add-on that allows you to run most old code, although no XS of course. There is also JERL that runs current microperl inside the JVM. It depends a lot on what you're looking to do, but those are worth checking out.

Answer 4

I've used Inline::Java a bit, and found it a bit fiddly, if I had my time over, I'd probably reimplement using web services and call the perl code that way.

Answer 5

Sleep is a scripting language with an interpreter that runs in the JVM. From what I understand the Sleep language is basically Perl with some extensions. Your code may be able to run in Sleep. If it does you can instantiate the interpreter, run the code and retrieve the result.