=head1 NAME

Inline::Java::Callback - Callback into Perl from Java.

=head1 SYNOPSIS

=for comment



=for comment


=head1 DESCRIPTION

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

=for comment

   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)CallPerl("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/) ;
   }

=for comment


=head1 CALLBACK API

Here are the various methods that one can use call into
Perl:

   public Object CallPerlSub(String sub, 
      Object args[], Class cast)
      throws InlineJavaException, InlineJavaPerlException
      
      Calls the specified subroutine with the supplied arguments and tries
      to create an object of type 'cast' with the result.
      Ex: Integer sum = (Integer)CallPerlSub("main::add", 
             new Object [] {new Integer(5), new Integer}, Integer.class) ;
      
   public Object CallPerlStaticMethod(String pkg, String method, 
      Object args[], Class cast) 
      throws InlineJavaException, InlineJavaPerlException
      
      Calls the specified static package method (using the $pkg->$method()
      notation) with the supplied arguments and tries to create an object 
      of type 'cast' with the result.
      Ex: Integer sum = (Integer)CallPerlStaticMethod("main", "add", 
             new Object [] {new Integer(5), new Integer}, Integer.class) ;

   public Object eval(String code, Class cast) 
      throws InlineJavaPerlException, InlineJavaException
      
      Evaluates the given Perl code and tries to create an object
      of type 'cast' with the result.
      Ex: Interger sum = (Integer)eval("5 + 3", Integer.class) ;

   public Object require(String module_or_file) 
      throws InlineJavaPerlException, InlineJavaException
      
      Requires the specified module/file by using the proper
      construct.
      Ex: require("Someting")
      
   public Object require_file(String file) 
      throws InlineJavaPerlException, InlineJavaException
      
      Requires the specified file.
      Ex: require("./my_stuff.pl") ;

   public Object require_module(String module) 
      throws InlineJavaPerlException, InlineJavaException
      
      Requires the specified module.
      Ex: require("Data::Dumper") ;


Note: For all CallPerl* and eval methods, the 'cast' parameter is optional
and defaults to 'String.class'.
	
These methods can throw 2 types of exceptions: C<InlineJavaException> and
C<InlineJavaPerlException> (both of these belong to the C<org.perl.inline.java>
package). The former designates an internal C<Inline::Java> error and the 
latter indicates that the Perl callback threw an exception (die() or croak()).
The value of $@ (this can be a scalar or any valid "Inline::Java" object) can
be retreived using the GetObject() method of the C<InlineJavaPerlException> object
(if you are certain that $@ was a Perl scalar, you can use the GetString() 
method).
   Z<>


=head1 CALLBACK LOOPS

It is now possible to use callbacks from different Java threads. One of the 
big advantages of this is that you can now handle, for example, SWING events 
in Perl. Here's an example:

=for comment

   use Inline Java => <<'END' ;
      import java.util.* ;
      import org.perl.inline.java.* ;
      import javax.swing.* ;
      import java.awt.event.* ;

      class Pod_Button extends InlineJavaPerlCaller
                       implements ActionListener {
         public Pod_Button() throws InlineJavaException {
            JFrame frame = new JFrame("Pod_Button") ;
            frame.setSize(100,100) ;
            JButton button = new JButton("Click Me!") ;
            frame.getContentPane().add(button) ;
            button.addActionListener(this) ;
            frame.show() ;
         }

         public void actionPerformed(ActionEvent e){
            try {
               CallPerl("main", "button_pressed", new Object [] {}) ;
            }
            catch (InlineJavaPerlException pe){
               // $@ is in pe.GetObject()
			}
            catch (InlineJavaException pe) {
               pe.printStackTrace() ;
            }
         }
      }
   END

   my $b = new Pod_Button() ;
   $b->StartCallbackLoop() ;

   sub button_pressed {
      print("click!\n") ; # prints click!
      $b->StopCallbackLoop() ;
   }

=for comment

The StartCallbackLoop method can be called on any InlineJavaPerlCaller object
and will block the current thread and allow the reception of callbacks through
any InlineJavaPerlCaller that has been created by the same (current) thread.
The only way to interrupt such a StartCallbackLoop method is to call the
StopCallbackLoop method on any C<org.perl.inline.java.InlineJavaPerlCaller> 
object that has been created by that same thread.

Also, only threads that communicate with Perl through C<Inline::Java> are allowed
to create C<org.perl.inline.java.InlineJavaPerlCaller> objects and invoke their 
StartCallbackLoop / StopCallbackLoop methods.
   Z<>


=head1 SEE ALSO

L<Inline::Java>, L<Inline::Java::PerlNatives>, L<Inline::Java::PerlInterpreter>.
   Z<>


=head1 AUTHOR

Patrick LeBoutillier <patl@cpan.org> is the author of Inline::Java.

Brian Ingerson <ingy@cpan.org> is the author of Inline.
   Z<>


=head1 COPYRIGHT

Copyright (c) 2001-2004, Patrick LeBoutillier.

All Rights Reserved. This module is free software. It may be used,
redistributed and/or modified under the terms of the Perl Artistic
License. See http://www.perl.com/perl/misc/Artistic.html for more
details.

=cut
