About for and inheritance
by Chris Woodrow
Hi,
I recently find out a few issues using for, and I wanted to share it with
you. I made a simple exemple to illustrate my purpose.
My classes are (I did not represent accessors & constructors):
public class Cheese {
protected String name;
}
public class FrenchCheese extends Cheese{
private String smell;
}
public class Person {
private Cheese likes;
}
Here is my rule set :
package rules
rule "likes cheese"
when
$person : Person ()
Cheese( ) from $person.getLikes()
then
System.out.println("likes cheese");
end
rule "likes french cheese"
when
$person : Person ()
FrenchCheese( ) from $person.getLikes()
then
System.out.println("likes french cheese");
end
First test :
Cheese cheese = new FrenchCheese("good", "camembert");
Person person = new Person();
person.setLikes(cheese);
Output :
likes french cheese
likes cheese
Wich is expected...
Second test :
Cheese cheese = new Cheese();
Person person = new Person();
person.setLikes(cheese);
Output :
likes french cheese
likes cheese
That's the first strange thing. As far as I am concerned, rule "likes french
cheese" should not match (since a Cheese is not a FrenchCheese).
I made a change to the second rule :
rule "likes french cheese"
when
$person : Person ()
FrenchCheese( smell == "good" ) from $person.getLikes()
then
System.out.println("likes french cheese");
end
Third test :
Cheese cheese = new Cheese();
Person person = new Person();
person.setLikes(cheese);
output :
It throwed an exception : Exception in thread "main"
java.lang.ClassCastException: rules.Cheese
I am not saying the ClassCastException is not to expect in such a case but I
think I would simply expect it not to match (as far as a Cheese is not a
FrenchCheese).
Chris
15 years, 5 months
Drools 4.0, Support for multiple pattern in accumulate source pattern
by Juergen
It appears as if accumulate does support only a single pattern CE as
source pattern, e.g.:
Number() from accumulate(
Cheese(
price : price
),
sum( price )
)
Is it possible to have more than one pattern in the source pattern, e.g.:
Number() from accumulate(
Cheese(
price : price,
type : type
)
Person(
favouriteCheese == type,
age > 30
),
sum( price )
)
The same could be said for collect, but there the problem to specify
which item of a matching tuple is to be collected, but this could be
handled recreating collect via accumulate, e.g.:
Collection() from accumulate(
cheese : Cheese(
type : type
)
Person(
favouriteCheese == type,
age > 30
),
collect( cheese )
)
15 years, 5 months
Blurring the lines of jBPM and Drools
by keithnielsen
I have been researching both jBPM and Drools for sometime now and am
wondering what the future holds for jBPM. This is based on my research of
Drools 5, which is bringing what I would consider more BPM constructs into
the core engine, things such as Wait States, Human Tasks, etc. One of the
main things I don't see yet is the whole persistence and support of long
running processes. My question is will the trend with Drools continue,
eventually consuming jBPM?
I must say that my perception is that Drools is more active which makes me
wonder if I should go with Drools hoping that it builds out more BPM
features going forward.
Thanks
--
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15 years, 7 months
Decision Tree input?
by Wilson O Ojwang
All,
Is there something in the works to support Decision Tree Inputs in
addition to Decision Table?
Regards
Wilson
15 years, 10 months
Conversion from Normal Decision Tables to Web-Based Tables and vice-versa
by Vikrant Yagnick
Hi All,
I am wondering if anyone has had a requirement where they would need to convert their normal decision tables into web-based decision tables(or vice-versa).
If someone has already done this, can they share either some code or pointers to how this can be done? (I guess it will involving parsing the Excel and creating the XML for the decision table).
Will this be a useful feature to have?
Cheers,
Vikrant
MASTEK LTD.
Mastek is in NASSCOM's 'India Top 20' Software Service Exporters List.
In the US, we're called MAJESCOMASTEK
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16 years, 8 months
loading rules dynamically
by techy
Hi,
If the rules,conditions,consequences have to loaded from the database. I
can think of following two approach. what would be right approach( I will
have upto 1200 rules in the db)
1. Programmatically inject the rules into rule engine using drools API.
2. Read the rules from the database and create drl or dsl file for them and
inject into rule engine.
Thanks
--
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16 years, 8 months
Why is a flat object recommended?
by Christie, Blair
In the documents this is dicussed briefly:
"). Object models can often have complex relationships and hierarchies
in them - for rules you will want to simplify and flatten the model
where possible, and let the rule engine infer relationships (as it
provides future flexibility."
What does it mean that the rule engine can infer relationships?
Are there performance reasons for having a flat model?
Cheers,
Blair
16 years, 10 months
Problems setting MySQL for the human task process server....
by Cristiano Gavião
Hi,
I was trying to change the persistence settings for human task process
server for using MySQL instead of H2DB.
I was following the Drools Flows Documentation on chapter 5.1.3.:
Configuring Persistence.(https://hudson.jboss.org/hudson/job/drools/lastSuccessfulBui...
#d0e1157)
I read on docs that I should override the persistence.xml of the
drools-process-enterprise.jar, create the drools.session.conf with
some contents (i don`t undestand` what it is...) and put them on my
project META-INF directory... ok?
I created the files as stated on docs but it didn't work... My
example runned ok, but using the H2DB and not my MYSQL.
// Use persistence.xml configuration
emf =
Persistence.createEntityManagerFactory("org.drools.persistence.jpa");
taskService = new TaskService(emf);
taskSession = taskService.createSession();
server = new MinaTaskServer(taskService);
Thread thread = new Thread(server);
thread.start();
Thread.sleep(500);
System.out.println("Server started ...");
<properties>
<property name="hibernate.dialect"
value="org.hibernate.dialect.MySQL5Dialect" />
<property name="hibernate.connection.driver_class"
value="com.mysql.jdbc.Driver" />
<property name="hibernate.connection.url" value="jdbc:mysql://
localhost/drools" />
<property name="hibernate.connection.username" value="root" />
<property name="hibernate.connection.password" value="" />
<property name="hibernate.connection.autocommit" value="false" />
<property name="hibernate.max_fetch_depth" value="3" />
<property name="hibernate.hbm2ddl.auto" value="create-drop" />
<property name="hibernate.show_sql" value="true" />
</properties>
After some investigation I could see that the example recommended by
Mark Proctor (TaskLifeCycleTest.java, and others that use
MinaTaskServer) use <persistence-unit name = "org.drools.task"> that
is setting on drools-process-task.jar and not the
"org.drools.persistence.jpa" on drools-process-enterprise.jar as
stated on documentation...
First question, which one should I use for use the Drools Flows Server
and Client?
emf =
Persistence.createEntityManagerFactory( "org.drools.task" );
emf =
Persistence.createEntityManagerFactory("org.drools.persistence.jpa");
I test the first option. I changed the persistence.xml file and use
the code below:
// Use persistence.xml configuration
emf = Persistence.createEntityManagerFactory("org.drools.task");
taskService = new TaskService(emf);
taskSession = taskService.createSession();
server = new MinaTaskServer(taskService);
Thread thread = new Thread(server);
thread.start();
Thread.sleep(500);
System.out.println("Server started ...");
Hummm.... It runs and connect well to my MySQL. but now it brings me a
error...
java.lang.IllegalArgumentException: Named query not found:
UnescalatedDeadlines
at
org
.hibernate
.ejb
.AbstractEntityManagerImpl
.createNamedQuery(AbstractEntityManagerImpl.java:108)
at org.drools.task.service.TaskService.<init>(TaskService.java:84)
at org.drools.task.service.TaskService.<init>(TaskService.java:68)
It sounds like it was not possible to find orm.xml that is on META-INF
of drools-process-task.jar.
But when I copy the orm.xml file to my project META-INF it works ok....
Could someone give some ideas how can I solve this problem..
Thanks a lot
Cristiano
16 years, 10 months
Drools Flow Trigger process by ruleset
by Garrett Conaty
I've seen in the latest docs on trunk that it's possible to set some
constraints on a start node so that a process would execute when the
appropriate rules matched.
However I can't see an example of this, nor can I edit the properties
through the Eclipse UI.
Is it possible to define a condition under which the process will
execute and then have the process start when the rule matches. Is
this done external to the rule file or can it be done on the rulefile
itself? I could see a few ways of doing this and am looking for some
guidance towards the correct (read as easiest for biz users) method.
1) Kick off a process that the first node after the start is a
ruleflow group (serving basically as a gate)
2) Deploy a rule that when it matches starts up the process (separate
rule file and separate ruleflow file)
3) Define a start condition in the rule file and deploy the process.
Then whenever the rule matches, a process instance is started.
Personally I like #3 and the docs seem to imply it's possible, but I
can't see how.
Thanks,
Garrett
17 years, 1 month
