Calling Perl routines from Java

package example.perl;
 
/***************************************************************
 * Download the jar for org.perl.inline.java first
 ****************************************************************/
 
// Perl file: StringDistance.pl
/*
 * #! /usr/bin/perl # Perl main program acting as a stub for callbacks from Java
 * 
 * use strict; use warnings;
 * 
 * # all modules called from either Perl or from Java must go here: use Text::Levenshtein qw();
 * 
 * use Inline "Java" => "STUDY", # glean interface from Java class file "AUTOSTUDY" => 1, # glean
 * more interfaces, too, just in case "STUDY" => ["StringDistance"], # name of our main Java class
 * "CLASSPATH" => ".", # needed in order to find main Java class ;
 * 
 * my $sd = StringDistance->new(\@ARGV); # construct instance of main Java class $sd->show(); # call
 * routine to show it $sd->StartCallbackLoop(); # prepare to listen for threaded callbacks
 */
 
/**
 * Example of a Java Class that calls a Perl function. <br/> Does not run on its own -- for usage,
 * see StringDistance.pl!
 */
 
import java.awt.Container;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
 
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
 
// requires classpath to include this file; usually something like
// .;<perldir>/site/lib/Inline/Java/InlineJavaServer.jar
 
/** The test class. */
public class StringDistance extends InlineJavaPerlCaller {
    JFrame frame; // visual container
    JTextField tf[], dist; // text input fields, result output field
    JButton go, exit; // action buttons
 
    /* The constructor with possibly 2 initial strings */
    public StringDistance(String[] strs) throws InlineJavaException {
	frame = new JFrame("StringDistance");
	Container p = frame.getContentPane();
	p.setLayout(new GridLayout(0, 2));
 
	// The input fields, including labels:
	tf = new JTextField[2];
	for (int i = 0; i < 2; i++) {
	    p.add(new JLabel("String " + i + ":"));
	    tf[i] = new JTextField(20);
	    if ((strs != null) && (i < strs.length))
		tf[i].setText(strs[i]);
	    p.add(tf[i]);
	}
 
	// The output field, including label:
	p.add(new JLabel("Distance:"));
	dist = new JTextField(5);
	dist.setEditable(false);
	p.add(dist);
 
	// The main action button:
	go = new JButton("Compute distance");
	go.addActionListener(new ActionListener() {
	    public void actionPerformed(ActionEvent ae) {
		dist.setText(Integer.toString(match(tf[0].getText(), tf[1].getText())));
	    }
	});
	p.add(go);
 
	// To finish off:
	exit = new JButton("Exit");
	exit.addActionListener(new ActionListener() {
	    public void actionPerformed(ActionEvent ae) {
		frame.dispose();
		System.exit(0);
	    }
	});
	p.add(exit);
 
	if ((strs != null) && (strs.length > 1))
	    dist.setText(Integer.toString(match(tf[0].getText(), tf[1].getText())));
	frame.pack();
    }
 
    // Alternative constructors:
    public StringDistance(String s0, String s1) throws InlineJavaException {
	this(new String[] { s0, s1 });
    }
 
    public StringDistance(String s0) throws InlineJavaException {
	this(new String[] { s0 });
    }
 
    public StringDistance() throws InlineJavaException {
	this((String[]) null);
    }
 
    /** This shows everything */
    public void show() {
	frame.setVisible(true);
    }
 
    /* Optionally for pre-filling the input fields. */
    public void setText(int fieldno, String str) {
	tf[fieldno].setText(str);
    }
 
    /** The central interface function to Perl. */
    public int match(String s0, String s1) {
	try {
	    String str = (String) CallPerl("Text::Levenshtein", "distance", new Object[] { s0, s1 });
	    return Integer.parseInt(str);
	} catch (InlineJavaPerlException e) {
	    System.err.println("Inline Java Perl Exception: " + e);
	} catch (InlineJavaException e) {
	    System.err.println("Inline Java Exception: " + e);
	}
	return 0;
    }
 
}