Hi Dave,

   Excellent!
   I will try to explain the current situation and one possible solution, but you may have better ideas.

   Functions in Drools are compiled as simple static methods in a generated java class. We use MVEL Templates to generate the code of the class and the static method.

   Take a look at JavaFunctionBuilder.java class for the code generation call and at javaFunction.mvel for the code template.

   Now, the problem with globals is that they are scoped to sessions, not rulebases, so you can not resolve them until runtime. You can not for instance, make them a static reference of the generated class and set it at rulebase compilation time.

   So, my suggestion would be to:

1. at compile time, use JavaDialect.analyzeBlock() method to analyze and find out what are the globals that are used by the funcion method code.

2. modify the code generation to add parameters to that in the method call. So, if "log" is a global and if the function is declared like this:

function void someFunction( String param ) {
    // ... code ...
    log.something(...);
    // ... code ...
}

   you detect the use of "log" and add it as a parameter of the generated method:

...
public static void someFunction( Logger log, String Param ) {
   ...
}
...

   This way, at runtime we can inject the parameter into the call. You can look at JavaConsequenceBuilder.java and javaInvokers.mvel to see how we do kind-of the same thing for consequences.

3. Now the most interesting part. :)  We use an ANTLR grammar for parsing Java code blocks. You need to change the parser to rewrite any function call the user is doing in his code to inject the log parameter transparently. I did the very same thing for modify blocks:

modify( $something ) {
   ...
}

   It is not hard once you get the hang of it. It is a bit of "hand work" though. Look at the JavaConsequenceBuilder.fixModifyBlocks() for what I did. Also, the ANTLR Java grammar is java.g.

   Let me know if you have questions or if you have a better idea, and welcome aboard!

   Cheers,
       Edson



2008/10/13 David Sinclair <dsinclair@chariotsolutions.com>
Hi Edson,

My name is dave sinclair. I started using Drools in early August of this year, but have a lot of experience with rules engines. I have worked primarily with ArtEntrprise and some with PegaRules. I would love to help with this project and thought that this may be the area to jump in on.

I have the M2 code, and was reading it over the weekend. Mostly the core and some of the compilier. If you want to point me in the right direction on the global/functions I'd be happy to have a look.

thanks

dave


On Mon, Oct 13, 2008 at 9:59 AM, Bagwell, Allen F <afbagwe@sandia.gov> wrote:
Edson,
 
Thanks for the tip. I figured I'd need to use a workaround like this.
 
Unfortunately I'm under a series of tight development and test deadlines all the way into early summer. Otherwise, I'd have a look. Hopefully someone else out there can assist.
 
Thanks,
-A

From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Edson Tirelli
Sent: Friday, October 10, 2008 5:46 AM
To: Rules Users List
Subject: Re: [rules-users] No globals in functions?


   Allen,

   There is a technical explanation behind that and we never had the time to find a way to overcome this limitation. What you can do, although not ideal, is to send the global as a parameter:

funcion void foo( Logger log, String cond )
{
...
}

rule XYZ
when
then
    foo( log, someString );
end

   If you or anyone would like to help improving this, let us know and we can discuss ways into doing it.

   []s
   Edson

2008/10/9 Bagwell, Allen F <afbagwe@sandia.gov>
 
There's probably an easy explanation for this. I was wondering about why functions inside of rule files can't access globals?
 
For example, I have a log4j logger that I pass into my rule files via a global.  The logger should never be a part of working memory. It's just there to capture valuable feedback.
 
But I can't do this:
 
global Logger log;
 
function void foo(String cond)
{
   if (cond == "error")
       log.error("I saw an error");
}
 
Because the compiler says that in the function it can't resolve 'log'.
 
-A
 
Allen F. Bagwell
phone:  505/284-4517
fax:  505/ 844-7886
 
There is no monument dedicated to the memory of a committee. -- Lester J. Pourciau
 
 
 

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--
 Edson Tirelli
 JBoss Drools Core Development
 JBoss, a division of Red Hat @ www.jboss.com

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--
 Edson Tirelli
 JBoss Drools Core Development
 JBoss, a division of Red Hat @ www.jboss.com