[rules-dev] Re: [rules-users] No globals in functions?

Greg Barton greg_barton at yahoo.com
Wed Oct 15 14:16:02 EDT 2008 

How about a ThreadLocal?

--- On Wed, 10/15/08, David Sinclair <dsinclair at chariotsolutions.com> wrote:

> From: David Sinclair <dsinclair at chariotsolutions.com>
> Subject: [rules-dev] Re: [rules-users] No globals in functions?
> To: "Edson Tirelli" <tirelli at post.com>
> Cc: "Mark Proctor" <mproctor at codehaus.org>, "Rules Dev List" <rules-dev at lists.jboss.org>
> Date: Wednesday, October 15, 2008, 12:53 PM
> What about injecting the globals into the classes and doing
> reflection to
> invoke the method dynamically? That way we would only need
> to change the
> JavaFunctionBuilder to rewrite the calls to the globals?
> For example
> 
> function foo() {
>     global.bar(abx);
> }
> 
> gets re-written as
> 
> function foo() {
>      method.invoke(global, [abx]);
> }
> 
> methods would be cached and such. Or do you guys not want
> the reflection in
> there?
> 
> 
> On Wed, Oct 15, 2008 at 1:45 PM, Edson Tirelli
> <tirelli at post.com> wrote:
> 
> >
> >    It may be invoked by a consequence, an eval, a
> predicate, or a return
> > value constraint.
> >
> >    If you fix it for the consequence in
> JavaConsequenceBuilder, the others
> > will work the same. You will have to change the java.g
> grammar as I
> > mentioned in my previousre e-mail to make it work.
> >
> >    []s
> >    Edson
> >
> > 2008/10/14 David Sinclair
> <dsinclair at chariotsolutions.com>
> >
> >  Edson,
> >> Changing the builder shouldn't be too much of
> a problem. If I make the
> >> changes you suggested, how does the global
> actually get passed to the
> >> method? For example if something defined a
> function like
> >>
> >> void function doX(int abc) {
> >>    ...
> >>    global.doY(bcd);
> >> }
> >> and I rewrite it to be
> >>
> >> void function doX(int abc, GlobalType global) {
> >>    ...
> >> }
> >>
> >> Who is the invoker of the method?
> >>
> >> thanks
> >>
> >> dave
> >>
> >>
> >>
> >>  On Mon, Oct 13, 2008 at 3:24 PM, Edson Tirelli
> <tirelli at post.com> wrote:
> >>
> >>>
> >>>    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 at 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 at 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 at lists.jboss.org [mailto:
> >>>>> rules-users-bounces at 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 at 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
> >>>>>> e-mail:  afbagwe at sandia.gov
> >>>>>> phone:  505/284-4517
> >>>>>> fax:  505/ 844-7886
> >>>>>>
> >>>>>> There is no monument dedicated to
> the memory of a committee. -- Lester
> >>>>>> J. Pourciau
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> _______________________________________________
> >>>>>> rules-users mailing list
> >>>>>> rules-users at lists.jboss.org
> >>>>>>
> https://lists.jboss.org/mailman/listinfo/rules-users
> >>>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>>> --
> >>>>>  Edson Tirelli
> >>>>>  JBoss Drools Core Development
> >>>>>  JBoss, a division of Red Hat @
> www.jboss.com
> >>>>>
> >>>>>
> _______________________________________________
> >>>>> rules-users mailing list
> >>>>> rules-users at lists.jboss.org
> >>>>>
> https://lists.jboss.org/mailman/listinfo/rules-users
> >>>>>
> >>>>>
> >>>>
> >>>
> >>>
> >>> --
> >>>  Edson Tirelli
> >>>  JBoss Drools Core Development
> >>>  JBoss, a division of Red Hat @ www.jboss.com
> >>>
> >>
> >>
> >
> >
> > --
> >  Edson Tirelli
> >  JBoss Drools Core Development
> >  JBoss, a division of Red Hat @ www.jboss.com
> >
> _______________________________________________
> rules-dev mailing list
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