From: David Sinclair <[EMAIL PROTECTED]>
Subject: [rules-dev] Re: [rules-users] No globals in functions?
To: "Edson Tirelli" <[EMAIL PROTECTED]>
Cc: "Mark Proctor" <[EMAIL PROTECTED]>, "Rules Dev List"
<[email protected]>
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
<[EMAIL PROTECTED]> 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
<[EMAIL PROTECTED]>
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
<[EMAIL PROTECTED]> 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
<[EMAIL PROTECTED]>
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 <[EMAIL PROTECTED]>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:*
[EMAIL PROTECTED] [mailto:
[EMAIL PROTECTED]
*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
<[EMAIL PROTECTED]>
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: [EMAIL PROTECTED]
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
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JBoss, a division of Red Hat @
www.jboss.com
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JBoss, a division of Red Hat @ www.jboss.com
--
Edson Tirelli
JBoss Drools Core Development
JBoss, a division of Red Hat @ www.jboss.com
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