12:06 a.m.
On 31/03/2012, Zeke <xanadu860122(a)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(a)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!
> >> >>
> >> >> _______________________________________________
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> >> >> rules-users@.jboss
> >> >> https://lists.jboss.org/mailman/listinfo/rules-users
> >> >>
> >> >>
> >> >
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> >> >
> >>
> >>
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