10:04 p.m.
I am trying to use drools to evaluate the following rule:
Given a telephone number, if the telephone number already exists in database
and has a balance > 0, set isAllowed = false. I cannot figure out how to
write the rule.
This is my object
public class Customer implements Serializable {
private static final long serialVersionUID = 1L;
private String tn;
private Double balance;
private Boolean isAllowed;
// getters/ setters
}
Can anyone help me with the rule below? The TN is set in the input fact. Is
the query below correct? It looks incorrect.
global org.hibernate.Session hibernateSession;
when
cust1:Customer()
cust2:Customer() from hibernateSession.createQuery("Select * from
Customers Where TN = :tn and balance >
0).setProperties({"tn":cust1.getTn()})list()
then
cust1.setIsAllowed(false);
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10:37 p.m.
First off, the query should be:
from Customers where TN = :tn and balance > 0
And that would be only if you mapped the tn property to the name "TN". HQL
queries are case sensitive when it comes to property names:
http://www.hibernate.org/hib_docs/v3/reference/en-US/html_single/#queryhq...
Second, I don't know if that whole "hibernateSession.createQuery" expression
would compile in a DRL file. Have you tried it? Anyone?
Finally, this rule will fire for every Customer in working memory and look up a matching
Customer in the database. Seems a bit inneficient, especially if you have many rules of
this type. Would it be possible to load the Customer from the database and just insert it
into working memory with it's "balance" property already set? That would
be far simpler. Then the rule would be:
global org.hibernate.Session hibernateSession;
when
cust1:Customer(balance > 0)
then
cust1.setIsAllowed(false);
hibernateSession.save(cust1);
end
(Ignoring the transaction management, here.)
You could even skip the save() on the hibernate session in the rule action. You could
keep the hibernate session open and save the Customers when you've completed all
changes.
--- On Tue, 3/31/09, Anu@work <anupama.vaid(a)bluecasa.com> wrote:
From: Anu@work <anupama.vaid(a)bluecasa.com>
Subject: [rules-users] Guvnor, database and rule language
To: rules-users(a)lists.jboss.org
Date: Tuesday, March 31, 2009, 3:04 PM
I am trying to use drools to evaluate the following rule:
Given a telephone number, if the telephone number already
exists in database
and has a balance > 0, set isAllowed = false. I cannot
figure out how to
write the rule.
This is my object
public class Customer implements Serializable {
private static final long serialVersionUID = 1L;
private String tn;
private Double balance;
private Boolean isAllowed;
// getters/ setters
}
Can anyone help me with the rule below? The TN is set in
the input fact. Is
the query below correct? It looks incorrect.
global org.hibernate.Session hibernateSession;
when
cust1:Customer()
cust2:Customer() from
hibernateSession.createQuery("Select * from
Customers Where TN = :tn and balance >
0).setProperties({"tn":cust1.getTn()})list()
then
cust1.setIsAllowed(false);
--
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http://www.nabble.com/Guvnor%2C-database-and-rule-language-tp22810206p228...
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Nabble.com.
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rules-users(a)lists.jboss.org
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11:40 p.m.
Thx. I now understand the part about the rule being fired for all customers
in memory. However, how do I achieve this on customer signup?
Given a TN in real time, I need to look up in the database if it is already
existing and if balance is greater than 0. If so, then do not allow signup.
btw, "hibernateSession.createQuery" expression validated in guvnor without
any problems. I had to declare hibernateSession as a global and set it in
the execution server. It actually fires also and I do nto see any errors but
I can't see the results anywhere.
Greg Barton wrote:
First off, the query should be:
from Customers where TN = :tn and balance > 0
And that would be only if you mapped the tn property to the name "TN". HQL
queries are case sensitive when it comes to property names:
http://www.hibernate.org/hib_docs/v3/reference/en-US/html_single/#queryhq...
Second, I don't know if that whole "hibernateSession.createQuery"
expression would compile in a DRL file. Have you tried it? Anyone?
Finally, this rule will fire for every Customer in working memory and look
up a matching Customer in the database. Seems a bit inneficient,
especially if you have many rules of this type. Would it be possible to
load the Customer from the database and just insert it into working memory
with it's "balance" property already set? That would be far simpler.
Then the rule would be:
global org.hibernate.Session hibernateSession;
when
cust1:Customer(balance > 0)
then
cust1.setIsAllowed(false);
hibernateSession.save(cust1);
end
(Ignoring the transaction management, here.)
You could even skip the save() on the hibernate session in the rule
action. You could keep the hibernate session open and save the Customers
when you've completed all changes.
--
View this message in context:
http://www.nabble.com/Guvnor%2C-database-and-rule-language-tp22810206p228...
Sent from the drools - user mailing list archive at Nabble.com.
6:22 p.m.
Drools is surprisingly one of the most intuitive tools I have used. I did
Java about 6 yrs back and most of the things I work on with Drools work the
first time or as soon as I get the basics right. So the code below works in
guvnor. I had to change the source code of the Drools Execution Server to
instantiate and pass a hibernateSession as a global to the drools stateless
session for rule execution.
I then defined hibernateSession as a global in guvnor and used it in a rule.
when
cust1:Customer();
cust:Customer() from hibernateSession.createQuery("from Customer where
custNbr=:custnbr").setProperties({"custnbr":cust1.getCustNbr()}).list();
then
cust1.setBalance(cust.getBalance());
cust1.setCustNbr(cust.getCustNbr());
Thx for your help Greg. And btw, I query for only one customer and I cannot
insert that one customer in working memory prior to rule because Drools
execution server is generic and does not know what client might request. But
this works.
--
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Greg Barton