Drools get facts from database at runtime - drools

Question

I need a little help with Drools eval and variable assigning.
rule "check that no previously submitted requests exist"
when
$user : UserFormField( name == 'employeeId', value != null )
$repository : Repository( )
$activeRequests : List( ) from $repository.findActiveRequestsByEmployee( $user.getValue() ) # call to repository
eval( $activeRequests.size() > 0 )
then
System.err.println(' You have active requests: ' + ((Request)$activeRequests.get(0)).getTitle);
insert(Boolean.TRUE);
end
In this rule I try to access repository and get active requests for current user. Rule compiles and executes without any exceptions or warnings. In debug mode it can be seen that repository returns non empty list and I expect to see console message 'You have active requests' but this doesn't happen. I think the problem is in this line
$activeRequests : List( ) from $repository.findActiveRequestsByEmployee( $user.getValue() )
because this rule works fine
rule "check that no previously submitted requests exist"
when
$user : UserFormField( name == 'employeeId', value != null )
$repository : Repository( )
eval( $repository.findActiveRequestsByEmployee($user.getValue()).size() > 0 )
then
System.err.println(' You have active requests !' );
insert(Boolean.TRUE);
end
So could someone point me how to solve this problem?
Thanks!

Answer 1

I was helped to find a solution. I should use from collect expression instead simple from to bundle facts into collection :
$activeRequests : ArrayList() from collect ( Request() from $repository.findActiveRequestsByEmployee( $user.getValue() ) )

Answer 2

You have to distinguish (i.e., read the fine print in the
documentation) between "from" and "from collect". If you want the rule
to fire individually for each collection element produced by the
expression after "from", then use "from". If, however, you want to
have it all bundled into a collection you must used "from collect".
$activeRequests : ArrayList() from collect ( Request() from
$repository.findActiveRequestsByEmployee( $user.getValue() ) )
Note that the separate eval isn't necessary. You can put this
constraint into the ArrayList pattern:
ArrayList( size > 0 )