[rules-users] ClassCastException when comparing date type with literal
Wolfgang Laun
wolfgang.laun at gmail.com
Sun Apr 1 03:29:16 EDT 2012
Surely you don't need examples for boolean expressions written in Java.
As for eval(), consult the Drools "Expert" manual, but there's not
much to say about it. Just note that you aren't in the context of a
pattern where "naked" fields can be used; within eval it's variables
bound to facts and getters.
-W
On 01/04/2012, Zeke <xanadu860122 at gmail.com> wrote:
> Thanks for your kindly reply. For the "mitigated restriction", do you mean
> I can use Order( eval( $msg.getDate().compareTo( new Date(...) ) ) ) # in
> 5.2.0 and 5.3.0? Can you give me any example or tell me any manual I can
> reference to?
>
> Thank you!
>
> On 31 March 2012 13:06, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:
>
>> On 31/03/2012, Zeke <xanadu860122 at gmail.com> wrote:
>> > It is just a test case used to bring up the issue. The real rule
>> condition
>> > in my business logic is more complex, like
>> > Order( id == '...', $msg.date > '...', num == $msg.num ). Of course I
>> > can
>> > change to use Message as Pattern to work aournd, but it is too tricky,
>> > right? And no matter the usage is weird or not, it is legal, right?
>> >
>>
>> I can't really say what was legal in 4.0.7, but
>> $msg: Message()
>> Order( $msg.date > '...' )
>> was not legal in 5.1.1. For any constraint, the left hand side would have
>> to
>> be a reference to a field of the fact where it occurs.
>> Order(Id == '...') # is OK
>> You can refer to fields of another fact on the RHS:
>> Order(num == $msg.num ) # is OK
>> Any other expression would have to be written in clean Java (or MVEL)
>> but enclosed in eval()
>> Order( eval( $msg.getDate().compareTo( new Date(...) ) == 1 ) ) # or
>> similar ;-)
>>
>> Starting with 5.2.0, this restriction was mitigated and by 5.3.0 and
>> certainly in 5.4.0 a wide range of (boolean) expressions is
>> acceptable.
>>
>> However, I should emphasize that postponing the use of a constraint
>> into a later pattern is an antipattern for rule coding. Consider
>> $msg: Message()
>> This matches any fact of type Message, and the Engine must needs keep
>> track of this. Contrariwise,
>> $msg: Message( date > "...")
>> narrows this effort down. Putting a constraint where it belongs is not
>> a "workaround", it's best practice :)
>>
>> -W
>>
>>
>> > I am using Drools 4.0.7. If later release fixes this bug, I may try to
>> > upgrade. I don't want to change LHS. It will bring much effort in my
>> > project.
>> >
>> >
>> > On 30 March 2012 14:09, FrankVhh <frank.vanhoenshoven at agserv.eu> wrote:
>> >
>> >> Let me rephrase my question:
>> >>
>> >> As date is an attribute of message, why don't you use:
>> >>
>> >> $msg : Message( date > "...")
>> >>
>> >> Constraining an attribute of Message in the Order pattern seems a weird
>> >> thing to do.
>> >>
>> >>
>> >>
>> >> Zeke-3 wrote
>> >> >
>> >> > It seems not work.
>> >> > When I try
>> >> > *$msg : Message($date : date)
>> >> > Order ( $date > "Mar-01-2012" )*
>> >> > I meet error "Unable to create Field Extractor for '$date' of
>> >> > '[ClassObjectType
>> >> > class=org.drools.examples.HelloWorldExample$Second]'
>> >> > in
>> >> > rule 'default' : [Rule name=default, agendaGroup=MAIN, salience=0,
>> >> > no-loop=false]"
>> >> >
>> >> > When I try
>> >> > *$msg : Message($date : date)
>> >> > eval ( $date > "Mar-01-2012" )*
>> >> > If the dialect is "java", I meet error "Rule Compilation error :
>> >> > [Rule
>> >> > name=default, agendaGroup=MAIN, salience=0, no-loop=false]
>> >> > org/drools/examples/test/Rule_default_0.java (8:354) : The
>> operator
>> >> > >
>> >> > is undefined for the argument type(s) Date, String"
>> >> > If the dialect is "mvel", I meet the same ClassCastException.
>> >> >
>> >> > On 29 March 2012 22:28, FrankVhh <frank.vanhoenshoven@> wrote:
>> >> >
>> >> >> This may sound a bit rude, but... why would you want to do such a
>> >> >> thing?
>> >> >>
>> >> >> If there is a constraint on the message, then why not put that
>> >> constraint
>> >> >> in
>> >> >> the message structure?
>> >> >>
>> >> >> Btw, I think it would work by using eval($date < "...") but see no
>> use
>> >> >> for
>> >> >> it either.
>> >> >>
>> >> >>
>> >> >> Joe Zendle wrote
>> >> >> >
>> >> >> > did you try:
>> >> >> >
>> >> >> > *$msg : Message($date : date)
>> >> >> > Order ( $date > "Mar-01-2012" )*
>> >> >> >
>> >> >> >
>> >> >> >
>> >> >> > 2012/3/29 Zeke <xanadu860122@>
>> >> >> >
>> >> >> >> Hi, guys:
>> >> >> >> I meet a strange issue and need your help again... I am using
>> >> Drools
>> >> >> >> 4.0.7.
>> >> >> >> When my rule condition is as *Message( date > "Mar-01-2012" )*,
>> >> >> >> everything is OK. But if I change it to be as below:
>> >> >> >> *$msg : Message()
>> >> >> >> Order ( $msg.date > "Mar-01-2012" )*
>> >> >> >> I will meet "java.lang.String cannot be cast to java.util.Date"
>> >> >> >> ClassCastException. "Order" is another fact. I attach the
>> exception
>> >> >> call
>> >> >> >> stack. Please check it. It looks like a bug to me. Do we fix it
>> >> >> >> in
>> >> >> later
>> >> >> >> release? If so, can you tell me which release contains the fix?
>> >> >> Thanks!
>> >> >> >>
>> >> >> >> _______________________________________________
>> >> >> >> rules-users mailing list
>> >> >> >> rules-users at .jboss
>> >> >> >> https://lists.jboss.org/mailman/listinfo/rules-users
>> >> >> >>
>> >> >> >>
>> >> >> >
>> >> >> > _______________________________________________
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>> >> >> >
>> >> >>
>> >> >>
>> >> >> --
>> >> >> View this message in context:
>> >> >>
>> >>
>> http://drools.46999.n3.nabble.com/rules-users-ClassCastException-when-comparing-date-type-with-literal-tp3867229p3867832.html
>> >> >> Sent from the Drools: User forum mailing list archive at Nabble.com.
>> >> >> _______________________________________________
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>> >> >
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>> >>
>> http://drools.46999.n3.nabble.com/rules-users-ClassCastException-when-comparing-date-type-with-literal-tp3867229p3870029.html
>> >> Sent from the Drools: User forum mailing list archive at Nabble.com.
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