Re: [rules-users] Benefits of pluggable operators
I'm inclined to think that a well-implemented operator can provide a
little bit more "cushioning" for the rule author. In the given
example, key.startsWith("abc") would throw an NPE if key is null. The
operator silently handle this case and simply return false.
Another thing is that operators can be used with the "single left hand
side" expression pattern, i.e.,
field opa x || opb y || opc y
Syntactic sugar, certainly, but occasionally quite convenient.
-W
On 24/05/2013, Edson Tirelli <ed.tirelli(a)gmail.com> wrote:
Thomas,
Pluggable operators were developed much before we supported free form
expressions, but nowadays they can be used for the same purpose. It is then
a matter of preference basically. You can still develop and use pluggable
operators if that makes your rule more readable by hiding complexity
related to parameter passing or something that would be required in a
method call, but I can't think of any advantage or disadvantage in either
approach in terms of performance or cost.
If I remember correctly, pluggable operators were developed for Drools
4.0, while free form expressions were only fully functional in 5.3+
(limited functionality in 5.2).
Edson
On Fri, May 24, 2013 at 10:54 AM, Thomas Grayson
<tgrayson(a)bluemetal.com>wrote:
> What are the benefits of using pluggable operators (implementations of
> org.drools.base.evaluators.EvaluatorDefinition such str, matches, or
> before) versus simply making an equivalent function call? I’ve read the
> Creating
> pluggable
> operators<http://blog.athico.com/2010/06/creating-pluggable-oprators.h...
> post. Apart from saying that the Eclipse plugin can recognize these
> operators, it doesn’t really make a case for why I’d want to create my
> own
> implementation. One might argue that operators enhance reusability, but
> a
> static method offers much the same benefit. Does a pluggable operator
> have
> any optimization, caching, or other advantage?****
>
> ** **
>
> For example, here are two ways to match the start of a string in a
> property of a fact, one using the “str[startsWith]” operator and another
> with Java’s String.startsWith method:****
>
> ** **
>
> *declare* Fact****
>
> key : String @key****
>
> *end*****
>
> ** **
>
> *rule* "Use operator"****
>
> *when*****
>
> Fact(key str[startsWith] "abc")****
>
> *then*****
>
> // do something****
>
> *end*****
>
> ** **
>
> *rule* "Use method"****
>
> *when*****
>
> Fact(key.startsWith("abc"))****
>
> *then*****
>
> // do something****
>
> *end*****
>
> ** **
>
> Does one of these perform better than the other?****
>
> ** **
>
> Best wishes,****
>
> Tom****
>
> ** **
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
--
Edson Tirelli
JBoss Drools Core Development
JBoss by Red Hat @ www.jboss.com