Re: Passing Hash values as Objects in Inline::Java

Ludovic Dubost Tue, 07 Oct 2003 01:09:48 -0700

Thanks..

I agree that making the result look as much as possible like the template toolkit expects it is the most safe way.. Especially since I continued a little trying to make the template toolkit work with a Hashtable.. I managed to stop is screaming but ti failed anyway because inside the template toolkit code, the perl hash is cloned and manipulated..

However it will not be so easy because the template toolkit can work with perl objects (that have the AUTOLOAD function) and it would be definitively interesting to allow the toolkit to be able to call back to the Java object.. Also the proposal of modifying the perl hash on the perl side is definitively the right way to go but it is not clear to me how to handle the nested hashes inside the main hash.. I'll try a little bit..

Anyway, in this process I made some modifications that make Inline::Java call the ->get and ->put functions of a Hashtable when it is asked to assign a value to it.. Wouldn't it be interesting to integrate such of functionality ?

Another thing I tried to modify is allowing to add a perl Hash to a Java Hashtable.. The way I did it was by leaving the hash on the perl wrapper of the Java object..

Ludovic

Patrick LeBoutillier wrote:

Ludovic,

What you are trying to do is very interesting, and it seems you are running into problems because template-toolkit uses the Perl-ism of stuffing everything into a big hash.

I think the best way for you to approach this is to keep your hash in Perl-land, and create functions, in Perl, to add things to it. You can then call these functions from Java using callbacks and construct you hash. Here's what I mean:

package myTT;
# Your hash stays here
my $H = {} ;
# Store a key, perhaps nested inside sub hashes.
sub put {
 my $key =shift ;
 my $val= shift ;
 my @path = split('.', $key) ;
 my $last = pop @path ;
 my $h = $H ;
 foreach my $p (@path){
 $h = $h->{$p} ;
 }
 $h->{$last} = $val ;
}
sub get {
 # Same logic...
}
By adding an extra attribute to 'put' you'll be able to handle special cases like function calls (i.e using "no strict 'refs'" and &{$val}) or whatever.

This way your data never leaves Perl and will be exactly the way template-toolkit wants it.

Good luck,
Patrick
----------------------------------
| Patrick LeBoutillier
| [EMAIL PROTECTED]
From: "Ludovic Dubost" <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Passing Hash values as Objects in Inline::Java
Date: Mon, 06 Oct 2003 19:37:20 +0200
Hi,

I'm trying to use Inline::Java to use the Perl Template Toolkit (http://www.template-toolkit.org/) from Java.. But I'm having little problems with communicating Hashtables to perl.

The way things work in the template toolkit is that you pass to templates a perl Hash that contains a lot of things.. It can contain functions, objects, hashes, arrays and strings..

What I would like to achieve is having some callbacks from the templates usage of all this to Java objects and functions.. For the moment I'm focusing on variables and objects:

Example template:
Version: [% VERSION %] 
Param 1: [% param1 %] 
Param 2: [% param2 %] 
Param 3: [% param3 %] 
Param 5: [% param5 %] 
Param 5 name: [% param5.name %] 
Param 5 value: [% param5.value %] 
Param 4 name: [% param4.name %] 
Param 4 value: [% param4.value %] 
Function call: [% Param('toto') %] 
If I have a perl Hash:
VERSION -> $vars{'VERSION'}
param1 -> $vars{'param1'}
param2 -> $vars{'param2'}
param3 -> $vars{'param3'}
param5.name -> $vars{'param5'}->{'name'}
param5.value -> $vars{'param5'}->{'value'}
Function call -> $vars{'Param'} is a function
param5.name could also be handled by an AUTOLOAD function if param5 is a perl object.

Using Inline::Java I've seen two solutions to make it work:

Solution 1: Make the template toolkit understand seemlessly the Java objects In this case the 'vars' variable would be a Hashtable.

So it would be:
VERSION -> vars.get('VERSION')
param1 -> vars.get('param1')
param5.name -> (Hashtable)vars.get('param1)).get('name')
I've managed to make the Inline::Java code call the 'get' or 'put' method when it doesn't find a member or a method.. I'm blocked because at one point the template toolkit wants to add a perl Hash to the vars Hashtable and Inline::Java does not want to convert such an object.. I'm thinking I would need to build a wrapper object in Java to store by Hash but I don't really know how to store by object, especially if I want to build a wrapper around the perl reference..

With this solution, I'm not sure how I can allow to call Java methods seemlessly.. Maybe just creating the perl wrapper will do it..

Solution 2: Allowing to manipulate perl hashes from Java

This solution is much safer at execution time as the data given to the template toolkit is much more close to what it gets in Perl. However this can be heavy as it might be needed to copy a lot of data and make a lot of call to perl to fill objects.. By trying this I found the same problem with hashes.. I was trying to store my perl hash in Java and then call perl functions to add data to it, but this was refused by the Inline module as it could not convert the Hash to a java object..

Any toughts in this area ? Is there a chance to make this work ?

Ludovic
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Re: Passing Hash values as Objects in Inline::Java

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