[rules-users] NullPointer in LHS dao calls ..
Sanjay Singh - s0singh
Sanjay.Singh at wal-mart.com
Tue Apr 3 18:29:42 EDT 2007
Since i could not get the earlier code running i tried using eval in LHS
side for Dao calls but i keep on getting NullPointerException ..
rule "Item should have a valid status"
when
ItemVo (statusCode : itemStatusCode != null)
eval( !itemValidationDao.isValidItemStatus(statusCode) )
then
errors.addValidationError("invalidtemStatusCode","Item Status Code is
invalid ");
end
Exception data: org.drools.RuntimeDroolsException:
java.lang.NullPointerException
at org.drools.rule.EvalCondition.isAllowed(Unknown Source)
at org.drools.reteoo.EvalConditionNode.assertTuple(Unknown Source)
at org.drools.reteoo.LeftInputAdapterNode.createAndAssertTuple(Unknown
Source)
at org.drools.reteoo.LeftInputAdapterNode.assertObject(Unknown Source)
at org.drools.reteoo.ObjectSource.propagateAssertObject(Unknown Source)
Can somebody please help .. thanks
________________________________
From: Sanjay Singh - s0singh
Sent: Tuesday, April 03, 2007 11:01 AM
To: 'Anstis, Michael (M.)'; Rules Users List
Subject: RE: Hi.
Thanks for getting back to me Mike and Edson and Sorry for the delayed
response.
I looked at your examples Mike and i felt better as you said that we can
make dao calls in LHS .. And Edson suggested not to be afraid of
suggesting the same constraint for more than one rule .. i guess i was
looking at it more procedural way and dint want any repetition of those
conditions as the top level IF block but looks like it won't hurt to
mention these constraints in all the rules related to this check ...so i
can include this check in all the rules .. hmm ..
Here is a quick test i was trying to do for calling the dao in LHS but
it fails .. what am i missing ..
package com.walmart.itemfile.item.rules
import com.walmart.itemfile.item.vo.ItemVo;
import com.walmart.itemfile.item.dao.ItemDao;
import com.walmart.itemfile.item.dao.ItemValidationDao;
import java.lang.String;
global com.walmart.itemfile.item.dao.ItemValidationDao
itemValidationDao;
global com.walmart.itemfile.rules.ValidationErrorMap errors;
rule "Item should have a valid status"
when
ItemVo( statusCode : itemStatusCode != null)
ItemVo( statusCode == true ) from
itemValidationDao.isValidItemStatus(statusCode) .. my isValidItemStatus
method returns a boolean (not collection of codes) and i need to check
if thats true than go to the RHS side .. is the line in green even right
... in any case it does not recognize itemValidationDao to begin with in
LHS side .. RHS same call works ..
then
errors.addValidationError("nullItemStatusCode","Item Status Code is
null");
System.out.println("Item Base Defaults Called" +
itemValidationDao.isValidItemStatus(statusCode));
System.out.println("Item Status Code is null");
end
Caused by: org.drools.rule.InvalidRulePackage: unknown:32:28 Unexpected
token 'itemValidationDao'
thanks for the help guys ..
Sanjay
________________________________
From: Anstis, Michael (M.) [mailto:manstis1 at ford.com]
Sent: Monday, March 26, 2007 8:57 AM
To: Rules Users List
Cc: Sanjay Singh - s0singh
Subject: RE: Hi.
Hi Sanjay,
To firstly answer your questions (in my opinion):
1. You can't do nested whens in the LHS but you can do nested if / else
in the RHS (although you'd fore go the benefits of a RETE-based
inference engine; but possible if you've got very few rules and
facts...). I believe that there is work to have an "otherwise" statement
for rule syntax, how progressed this is and how it will work I don't
know - over to Mark and team?!?
2. Yes, take a look at the "from" statement (new for 3.1-M1, see
http://wiki.jboss.org/wiki/Wiki.jsp?page=3.1M1ReleaseNotes)
3. Yes, take a look at rule-flow at
http://labs.jboss.com/portal/index.html?ctrl:cmd=render&ctrl:window=defa
ult.blog.PrjBlogPortletWindowDefaultBlog&project=jbossrules&from=1&link=
RuleFlow_%28Kris_Verlaenen%29#RuleFlow_%28Kris_Verlaenen%29 (although I
don't know if this is complete if 3.1-M1 - I think it's not). Although I
don't think your rules really need rule-flow; you just need to identify
and isolate the patterns (IF's) that would cause each "Do Something" to
be ran and create a rule for each - this has the benefit of separating
each action into a separate rule making maintenance a whole bunch
easier).
Anyway, I'd try some rules like the following examples (the rest are
based upon these):-
Rule "Rule 1"
when
NewItem ( itemStatusCode == null)
then
//do something
end
Rule "Rule 2"
when
$u : User( )
$ni : NewItem ( $isc : itemStatusCode != null )
not Codes ( codes contains $isc ) from
valDao.getValidItemStatusCodesForUser($u)
then
//Do something
end
Rule "Rule 3"
when
$u : User( )
$ni : NewItem( itemStatusCode == ItemVO.DELETED )
Codes ( codes contains $isc ) from
valDao.getValidCrossReferencePrimeCodesForUser($u)
then
//Do something
end
I've posted to the news group so everyone can contribute - don't be shy
;-)
With kind regards,
Mike
________________________________
From: Sanjay Singh - s0singh [mailto:Sanjay.Singh at wal-mart.com]
Sent: 26 March 2007 14:24
To: Anstis, Michael (M.)
Subject: Hi.
Hey Mike ... I am sorry to bother you but you seemed to be
pretty good with rules and i just could not think of anyone else to ask
abt it ... I am sorry if i am taking much of your time .. Here is my
problem if you can have a quick look ..
Look at this code once .. its very easy but it involves tons of
if else blocks conditions ..
if( newItem.getItemStatusCode() == null){
//do something
}
else{
if(
!valDao.isValidItemStatus(newItem.getItemStatusCode(),user) ){
//do something
}
if(
newItem.getItemStatusCode().equals(ItemVo.DELETED)||getItemStatusCode().
equals(ItemVo.INACTIVE) ){
if(
valDao.isCrossReferencePrime(newItem.getItemNbr(),user)){
//do something
}
else if(
valDao.isFutrCrossReferencePrimeOrSecond(newItem.getItemNbr(),user) ){
//do something
}
else if(
valDao.isComponentLink(newItem.getItemNbr(),user)){
//do something
}
else if(
valDao.hasWhseOnHandsOrOnOrders(newItem.getItemNbr(),user)&&CountryCode(
).equals("CA") ){
//do something
}
}
else{
if(
valDao.isUnlikeAsstParentWithNonActiveChildren(newItemNbr,user) ){
//do something;
}else if
(isLikeAssortmentBaby(newItemNbr,user)&&!alDao.isLikeAsstParentActive(ne
wItemNbr, user)){
//do something
}else{
//do something
}
}
}
}
What i am trying to understand is the right way of putting it in
drl files ..
1.What are the options for putting if else conditions ? Will i
have to write all the rules anyway and they will be called as well all
the time depending on the criteria ... or is there a way where when my
first if check which was if item number is null failed i should not go
for any other rules .. Is there a way where we could have like "when"
inside "when" .. kinda looping of conditions so if one does not meet you
dont go to the next .. jsut like in above blocks ? Whats the good way of
doing it ?
2.Is it possible to make database calls like from my dao
instance in LHS (condition) .. i know we can do it in RHS and i have
tested that as well but can we do it in LHS as sometimes we need to do
that ..like with null checks for the item status code we also want to
check something from the database like a boolean value and if that meets
the criteria we will run the rules ..as u can see above we have basic
state check with nulls etc plus we have some dao calls as well in the
condition part and then we //do something
3.Can i call rules within other rules .. so something like in
rule1 i want to call rule2 .. is that possible ?
Can you suggest a decent way of doing these if else blocks ..
this is the core stuff which we do for our rules here .. if i can handle
this kind of conditions i guess i can handle anything out here ...
Thanks for all the help ..
Sanjay
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