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

I don't know how stable will that be ,or how well maintained it is, so, another option would be to write a script that does something your application will need and then execute that script from Java. Not the most elegant way, but it works.

Answer 3

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

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

Or am I misunderstanding the question?

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

I found an implementation on JavaWorld by Robert Lawson, which uses XML-RPC to call Perl routines from your Java code: Call Perl routines from Java

Answer 6

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.