[rules-users] Benefits of pluggable operators

[Edson Tirelli]

   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 at 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.html>blog 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****
>
> ** **
>
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>



-- 
  Edson Tirelli
  JBoss Drools Core Development
  JBoss by Red Hat @ www.jboss.com
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