Leonardo Gomes wrote: > Regarding the problem with dates, even when using java beans, what > options would I have other than accepting the limitations of that > syntax sugar or to provide a static method, casting and converting > arguments, returning a boolean, and call this using an inline eval. If I'm not mistaken, in drools 5 you can declare (and even define) functions which can be called without eval(). So you'd provide that static method, declare it in DRL & at least get rid of eval().
Also, I think there's a smoother syntax to acces maps, the mvel page explains it. Short version this["foo"] -> foo. Or something. > > Thanks again, > > Leo. > > 2009/11/8 Edson Tirelli <ed.tire...@gmail.com>: >> Wolfgang, >> >> As you know, there are a ton of problems when you go down the "date" >> route. Probably the reason java never had a decent built-in date framework >> (fingers crossed for JSR-310). >> >> Anyway, back to the point, the syntax sugar for string-based strings is a >> really simple way for people to use really simple dates in their rules. But, >> yes, with that, you can't define which calendar, timezone, daylight savings, >> etc, rules should use. It will just use the defaults for the JVM instance. >> You will probably never see *me* using that. But there are people that just >> want something that simple and in this case, it is there. >> >> MVEL page is: >> >> http://mvel.codehaus.org/ >> >> I don't think that mvel has anything specific to dates, but I might be >> wrong. >> >> The only thing "not available" in Drools are the control structures >> (if/while/etc) that we disable explicitly. >> >> Edson >> >> 2009/11/8 Wolfgang Laun <wolfgang.l...@gmail.com> >>> For the sake of clarification: Are you saying that there is, or should be, >>> some magic which would make a constraint like >>> Map ( this["departureDate"] == "07-Jan-2009" ) >>> behave as a comparison between two java.util.Date values if the LHS Object >>> is of this type? And also if it is a GregorianCalendar object? >>> >>> Since even you are "not sure" regarding MVEL: What is the definite >>> reference for MVEL in Drools? I have a vague recollection of reading >>> somewhere that not all of MVEL is available... >>> >>> -W >>> >>> >>> 2009/11/8 Edson Tirelli <ed.tire...@gmail.com> >>>> Ok, without discussing the merits of using (or not) maps, the reason >>>> you are having problems with dates is that the "string-based" date is >>>> syntax >>>> sugar in Drools parser/compiler. Although, when you create expressions >>>> using >>>> nested accessors or [] for collection/map element access, drools wraps the >>>> whole thing into an "eval" and delegates to MVEL. We do some >>>> transformations >>>> to bridge the gap between drools operators and mvel operators, but I don't >>>> think drools has anything to "transform" the string-based date into >>>> something mvel understands. >>>> >>>> Having said that, we should probably add this functionality to the >>>> "MVELDumper" class for better integration. Would you please open a jira for >>>> that? Also, patches are welcome in case someone would like to help. This is >>>> an isolated part of the code and easy to understand. >>>> >>>> Meanwhile, best you can do is avoid the use of this Map syntax + >>>> string-based dates, or write your expressions directly in a way the mvel >>>> understands (not sure mvel has a special syntax for dates). >>>> >>>> Same explanation for the NPE. >>>> >>>> Edson >>>> >>>> 2009/11/8 Leonardo Gomes <leonardo.f.go...@gmail.com> >>>>> Hi Wolfgang, >>>>> >>>>> Here's the context: >>>>> >>>>> We're replacing a very basic home-made rule engine with drools. Today, >>>>> fact data can be added dynamically b/c for all rules our fact is >>>>> nothing more than a Map and we can register new fact data through an >>>>> UI where you say what's the key and what's the type of the value. >>>>> Rules can also be created dynamically and operate against those newly >>>>> created attributes of my fact. >>>>> >>>>> Incoming requests are key / value structures and we have a service >>>>> that will look at the list of registered fact data and try to find >>>>> that information in the incoming request by looking for the keys and >>>>> getting the corresponding values, then populating the Map I just >>>>> talked about which will be injected in the working memory for >>>>> evaluation against our rules. >>>>> >>>>> That's why, in Drools, I need to have my rules accessing data from a >>>>> Map. By using MVEL, as I said, it works fine with strings, integers >>>>> and list of strings, but I'm having problems with dates and would like >>>>> some advice on that case. >>>>> >>>>> Here's another example of things that work: >>>>> >>>>> rule "test rule" >>>>> when >>>>> Map ( this["airportCode"] == "GIG" >>>>> , this["numberOfPassengers"] > 1 >>>>> , this["class"] in ("BUSINESS", "FIRST CLASS") ) >>>>> then >>>>> m.addMessage("rule matched"); >>>>> end >>>>> >>>>> And here's where I have problems, >>>>> >>>>> Map ( this["departureDate"] ) == "07-Jan-2009" ) >>>>> >>>>> >>>>> Thanks a lot, >>>>> Leo. >>>>> >>>>> >>>>> >>>>> On Sun, Nov 8, 2009 at 10:56 AM, Wolfgang Laun <wolfgang.l...@gmail.com> >>>>> wrote: >>>>>> On Sat, Nov 7, 2009 at 6:00 PM, Leonardo Gomes >>>>>> <leonardo.f.go...@gmail.com> >>>>>> wrote: >>>>>>> Hello, >>>>>>> >>>>>>> I'm feeding my working memory with Maps (unfortunately, this is a >>>>>>> requirement and I can't use beans). >>>>>>> >>>>>> Before people start racking their brains to overcome all the resulting >>>>>> difficulties: Could you please explain what this requirement is meant >>>>>> to >>>>>> achieve? >>>>>> -W >>>>>> >>>>>> >>>>>>> To access the values in this maps I use the following MVEL expression >>>>>>> : >>>>>>> >>>>>>> Map ( this["airportCode"] == "GIG" >>>>>>> , this["numberOfPassengers"] > "1" >>>>>>> , this["class"] memberOf ("BUSINESS", "FIRST") >>>>>>> ) >>>>>>> >>>>>>> And it works fine, except for dates where I get a ClassCastException, >>>>>>> even tough I'm using the right pattern: >>>>>>> >>>>>>> Map ( this["departureDate"] > "07-Nov-2009" ) --- fails >>>>>>> >>>>>>> Is there anything I need to do to make the dynamic cast of dates >>>>>>> work, >>>>>>> in this particular case? >>>>>>> >>>>>>> -- >>>>>>> >>>>>>> Morever, I get NPEs if there's no value for a given key. For example, >>>>>>> the expression Map ( this ["name"] == 'Leonardo' ) would fail if >>>>>>> there's no entry with "name" as the key. >>>>>>> >>>>>>> Any help is welcome! >>>>>>> >>>>>>> Thanks in advance, >>>>>>> Leo. >>>>>>> _______________________________________________ >>>>>>> rules-users mailing list >>>>>>> rules-users@lists.jboss.org >>>>>>> https://lists.jboss.org/mailman/listinfo/rules-users >>>>>> >>>>> _______________________________________________ >>>>> rules-users mailing list >>>>> rules-users@lists.jboss.org >>>>> https://lists.jboss.org/mailman/listinfo/rules-users >>>> >>>> >>>> -- >>>> Edson Tirelli >>>> JBoss Drools Core Development >>>> JBoss by Red Hat @ www.jboss.com >>>> >>>> _______________________________________________ >>>> rules-users mailing list >>>> rules-users@lists.jboss.org >>>> https://lists.jboss.org/mailman/listinfo/rules-users >>>> >>> >>> _______________________________________________ >>> rules-users mailing list >>> rules-users@lists.jboss.org >>> https://lists.jboss.org/mailman/listinfo/rules-users >>> >> >> >> -- >> Edson Tirelli >> JBoss Drools Core Development >> JBoss by Red Hat @ www.jboss.com >> >> _______________________________________________ >> rules-users mailing list >> rules-users@lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/rules-users >> >> > > _______________________________________________ > rules-users mailing list > rules-users@lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users > _______________________________________________ rules-users mailing list rules-users@lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users
