You should read at least chapter 4 of
http://downloads.jboss.com/drools/docs/5.0.1.26597.FINAL/drools-expert/html/index.html
where eval() and everything else you can use in a rule is described.

Using output statements on the left hand side of a rule is not a very good way of determining whether a rule fires or not. Using the KnowledgeRuntimeLogger (see section 3.3.6) might be a better way of seeing what goes on in your rule based system.

There is no special class for methods you can call in an eval(). An import (in the .drl file) may be required if it is a static method. In any case, an expression used inside eval() must result in a boolean value.

-W


2010/4/30 Puneet duggal <duggalpunit@gmail.com>
thanks for ur reply friend,
 
can u tell me how to use eval()
and in which class do i have to
put my function which i  have to call  it from eval() function  
 

 
On 4/30/10, Esteban Aliverti <esteban.aliverti@gmail.com> wrote:
You can't directly use java code inside the LHS of a rule. You can though use eval to call a java method inside your LHS. Also remember that you don't have to use ; in the patterns.  

2010/4/30 Puneet duggal <duggalpunit@gmail.com>
frnds i have a rule
 
and its not working and i  for checking i have put a Sop in my  when  but it not  prints  the 
Inside Area_SqFt_1_10-01-09_12-31-14
so how can we put SOP inside when clause.

rule "Area_SqFt_1_10-01-09_12-31-14"

date-effective "01-Oct-2009" date-expires "31-Dec-2014" salience 6

no-loop true

when

System.out.println("Inside Area_SqFt_1_10-01-09_12-31-14");

objectP2483 : Para_2483( (fid2335=="Block") && (fid2336==16) );

then

System.out.println("Area_SqFt_1_10-01-09_12-31-14");

objectP2483.setFid31003(new Double(497)); end


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