The document provides a hands-on training course for Drools 5, focusing on various aspects such as rule activation, conditional elements, and rule attributes through examples and exercises. It includes detailed instructions on using the Drools framework, with project references, test classes, and specific tasks for participants. The course is licensed under Creative Commons and encourages participants to seek feedback and ask questions.

1.
Drools5 Community Training
Hands On Playing with Rules
Sponsored by Plugtree

2. Hands On 1: Drools Expert
Playing with Rules
Drools5 Community Training
version: 1.0-SNAPSHOT
Release Date: 09/05/2011
Under The Creative Common License

3. Hands On 1: Drools Expert
Playing with Rules
Drools5 Community Training Course
by Mauricio "Salaboy" Salatino and
Esteban Aliverti is licensed under a
Creative Commons Attribution 3.0
Unported License.
Based on a work at salaboy.wordpress.
com.
Permissions beyond the scope of this
license may be available at http:
//salaboy.wordpress.com/.

4. Overview
● Drools Expert Examples
○ Introduction examples
○ Conditional elements examples
○ Rules Attributes examples

5. Introduction Examples
● Project: drools5/01-DroolsExpert-Introduction
● Test: SimpleRulesExampleTest.java
● Rules: src/main/resources/rules/rules.drl
● Kbuilder, Kbase and Ksession (createKSession() method)
○ Take a look at the addEventListener() method
● DRL syntax in the rule file:
○ Take a look at the LHS
○ Take a look at the RHS
● Rules activation and execution (you can activate the logger)

6. Introduction Examples
● Exercise
○ Find a way to get "Warn when we have a POP songs and
Playlist" Rule activated but not fired.
○ Find a way to get "Warn when we have a POP songs and
Playlist" Rule activated and fired.

7. Conditional Elements examples
● Project: drools5/02-DroolsExpert-ConditionalElements
● Simple Rules Example:
○ Test Class: SimpleRulesExampleTest.java
○ Rules: SimpleRules.drl
○ Conditional Elements on LHS
○ from Conditional Element
● Advanced from Examples:
○ Test Class: AdvancedFromRulesExampleTest.java
○ Rules: AdvancedFromRules.drl
○ collect, accumulate, accumulate custom function, Using
Hibernate session in from CE

8. Conditional Elements Examples
● Exercise 1
○ Replace "Add Playlists that contains songs with letter 'a'
in their titles to the list using the accumulate conditional
elements defining init, action, reverse and result functions.
i.e:
from accumulate(
$s: Song() from $songs,
init(),
action(),
reverse(),
result()
)

9. Conditional Elements examples
Solution:
rule "Playlists that contains songs with letter 'a' in their titles."
when
$playlist: Playlist($songs: songs)
$match: java.util.List(empty == false) from accumulate(
$s: Song() from $songs,
init( java.util.List result = new java.util.ArrayList();),
action( if ($s.getTitle().contains("a")) result.add($s); ),
result( result )
)
then
System.out.println("Playlist found: "+$playlist);
for (int i=0; i<$match.size(); i++){
System.out.println("t--"+$match.get(i));
}
end

10. Conditional Elements examples
● Exercise 2
○ Create a custom accumulate function to collect random
songs from a playlist.
○ Copy the SongsWithALetterOnTheirTitlesFunction.java implementation

11. Conditional Elements Examples
● eval Example:
○ Test Class: EvalRulesExampleTest.java
○ Rules: /rules/EvalRules.drl
○ use of eval in LHS
● exists Example:
○ Test Class: ExistsRulesExampleTest.java
○ Rules: ExistsRules.drl
○ use of exists and not in the LHS

12. Conditional Elements Examples
● Exercise
○ Replace "Warn when we have a Playlist longer than 9000
seconds" with an equivalent Rule without using eval

13. Conditional Elements Examples
Solution
rule "Playlist longer than 9000 seconds without eval"
when
$playlist: Playlist($songs: songs) AND
$n : Number(intValue > 9000) from accumulate(
$s : Song() from $songs,
sum($s.getDuration()))
then
System.out.println("We have found a Playlist
longer than 9000 seconds");
end

14. Rule Attributes examples
● Project: drools/03-DroolsExpert-RulesAttributes
● Test Class: RuleAttributesExampleTest.java
● Attributes:
○ salience
○ no-loop:
■ Test: noLoop() Rules: /rules/NoLoopRules.drl
○ lock-on-active:
■ Test: lockOnActive() Rules: /rules/LockOnActiveRules.drl
○ agenda-group:
■ Test: agendaGroup() Rules: /rules/AgendaGroupRules.drl

15.
Questions?

16. Enjoy! Questions and Feedback are
always appreciated!

17.
Contact us at
www.plugtree.com