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<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>Hello all,
</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>I am about a day old
to Drools. I have had success in executing the examples in a Windows, JDK1.6
environment. </FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>Based on the success
of the examples, I am trying to put together a sample usecase myself to
understand Drools. I write to you since I havent had much success in that.
</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>My use case is:
</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>1) Check the type of
person.</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>2) If person is an
Employee, then print the Employee ID. </FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>3) If person is a
customer then print the customer first and last name.</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>4) If the person is
an Employee and the employee id is missing, then throw an exception, so that the
calling API can handle the error.</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>To realize this, I
have three interfaces, IPerson, IEmployee extends IPerson and ICustomer extends
IPerson. </FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>IPerson has the
common attribute getters such as; getFirstName, getLastName</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>IEmployee has the
getter getEmployeeId, while the ICustomer is only a marker interface (at the
moment). </FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>The DRL file with
the rules contains: </FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>rule "If no Employee
Number, then print error"<BR> dialect
"java"<BR> when<BR> IPerson( empNumber <= -1
)<BR> then<BR> System.out.println( "Invalid Employee number"
);<BR>end</FONT></SPAN></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV><SPAN class=467094722-29112007>
<DIV><BR><FONT face=Arial size=2>rule "Rule to print the Employee
number"<BR> dialect
"mvel"<BR> when<BR> $person : IPerson( personType ==
IPerson.EMPLOYEE_PERSON_TYPE )<BR> then<BR> System.out.println(
"The Employee Number is "+$person.empNumber);<BR>end</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><BR><FONT face=Arial size=2>rule "Rule to print the first name and last
name if it is a Customer"<BR> dialect
"mvel"<BR> when<BR> $person : IPerson( personType ==
IPerson.CUSTOMER_PERSON_TYPE )<BR> then<BR> System.out.println(
"The Customers' name is "+$person.firstName+" "+$person.lastName
);<BR>end</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>The error I get for
the rule is:</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>Unable to create
Field Extractor for 'empNumber' of '[ClassObjectType
class=com.drools.local.samples.model.IPerson]</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>The above error did
suggest that the IPerson doesnot expose any methods to retrieve the empNumber,
such as getEmpNumber. But then, when I do a $person.empNumber, it does print the
empNumber. Hence, the Drools framework must somehow be able to *auto-magically*
cast down the object. This is what is confusing me. </FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>Could you advice if
my usecase is possible with Drools and if yes, then what am I missing? Is my
rules approach wrong? Also, if there a way to throw exceptions in the then
case?</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>The JSR-94 provides
mechanism to get the results, is there a similar way in
Drools?</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial
size=2>Thanks.</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial
size=2>Cheers</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial size=2>Gautham
Kasinath</FONT></SPAN></DIV>
<DIV><SPAN class=467094722-29112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><FONT face=Arial size=2></FONT></SPAN> </DIV></BODY></HTML>
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