Chapter 20. Other methods for creating and executing DRL rules
As an alternative to creating and managing DRL rules within the Business Central interface, you can create DRL rule files externally as part of a Maven or Java project using Red Hat CodeReady Studio or another integrated development environment (IDE). These standalone projects can then be integrated as knowledge JAR (KJAR) dependencies in existing Red Hat Decision Manager projects in Business Central. The DRL files in your standalone project must contain at a minimum the required package
specification, import
lists, and rule
definitions. Any other DRL components, such as global variables and functions, are optional. All data objects related to a DRL rule must be included with your standalone DRL project or deployment.
You can also use executable rule models in your Maven or Java projects to provide a Java-based representation of a rule set for execution at build time. The executable model is a more efficient alternative to the standard asset packaging in Red Hat Decision Manager and enables KIE containers and KIE bases to be created more quickly, especially when you have large lists of DRL (Drools Rule Language) files and other Red Hat Decision Manager assets.
20.1. Creating and executing DRL rules using Java
You can use Java objects to create DRL files with rules and integrate the objects with your Red Hat Decision Manager decision service. This method of creating DRL rules is helpful if you already use external Java objects for your decision service and want to continue with the same workflow. If you do not already use this method, then the Business Central interface of Red Hat Decision Manager is recommended for creating DRL files and other rule assets.
Procedure
Create a Java object on which the rule or rules will operate.
In this example, a
Person.java
file is created in a directorymy-project
. ThePerson
class contains getter and setter methods to set and retrieve the first name, last name, hourly rate, and the wage of a person:public class Person { private String firstName; private String lastName; private Integer hourlyRate; private Integer wage; public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public Integer getHourlyRate() { return hourlyRate; } public void setHourlyRate(Integer hourlyRate) { this.hourlyRate = hourlyRate; } public Integer getWage(){ return wage; } public void setWage(Integer wage){ this.wage = wage; } }
Create a rule file in
.drl
format under themy-project
directory. The DRL file must contain at a minimum a package specification (if applicable), an import list of data objects to be used by the rule or rules, and one or more rules withwhen
conditions andthen
actions.The following
Wage.drl
file contains aWage
rule that calculates the wage and hourly rate values and displays a message based on the result:package com.sample; import com.sample.Person; dialect "java" rule "Wage" when Person(hourlyRate * wage > 100) Person(name : firstName, surname : lastName) then System.out.println("Hello" + " " + name + " " + surname + "!"); System.out.println("You are rich!"); end
- Create a main class and save it to the same directory as the Java object that you created. The main class will load the KIE base and execute rules.
In the main class, add the required
import
statements to import KIE services, a KIE container, and a KIE session. Then load the KIE base, insert facts, and execute the rule from themain()
method that passes the fact model to the rule.In this example, a
RulesTest.java
file is created inmy-project
with the required imports andmain()
method:import org.kie.api.KieServices; import org.kie.api.runtime.KieContainer; import org.kie.api.runtime.KieSession; public class RulesTest { public static final void main(String[] args) { try { // Load the KIE base: KieServices ks = KieServices.Factory.get(); KieContainer kContainer = ks.getKieClasspathContainer(); KieSession kSession = kContainer.newKieSession(); // Set up the fact model: Person p = new Person(); p.setWage(12); p.setFirstName("Tom"); p.setLastName("Summers"); p.setHourlyRate(10); // Insert the person into the session: kSession.insert(p); // Fire all rules: kSession.fireAllRules(); kSession.dispose(); } catch (Throwable t) { t.printStackTrace(); } } }
-
Download the Red Hat Process Automation Manager 7.13.5 Source Distribution ZIP file from the Red Hat Customer Portal and extract it under
my-project/dm-engine-jars/
. In the
my-project/META-INF
directory, create akmodule.xml
metadata file with the following content:<?xml version="1.0" encoding="UTF-8"?> <kmodule xmlns="http://www.drools.org/xsd/kmodule"> </kmodule>
This
kmodule.xml
file is a KIE module descriptor that selects resources to KIE bases and configures sessions. This file enables you to define and configure one or more KIE bases, and to include DRL files from specificpackages
in a specific KIE base. You can also create one or more KIE sessions from each KIE base.The following example shows a more advanced
kmodule.xml
file:<?xml version="1.0" encoding="UTF-8"?> <kmodule xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.drools.org/xsd/kmodule"> <kbase name="KBase1" default="true" eventProcessingMode="cloud" equalsBehavior="equality" declarativeAgenda="enabled" packages="org.domain.pkg1"> <ksession name="KSession1_1" type="stateful" default="true" /> <ksession name="KSession1_2" type="stateful" default="true" beliefSystem="jtms" /> </kbase> <kbase name="KBase2" default="false" eventProcessingMode="stream" equalsBehavior="equality" declarativeAgenda="enabled" packages="org.domain.pkg2, org.domain.pkg3" includes="KBase1"> <ksession name="KSession2_1" type="stateless" default="true" clockType="realtime"> <fileLogger file="debugInfo" threaded="true" interval="10" /> <workItemHandlers> <workItemHandler name="name" type="new org.domain.WorkItemHandler()" /> </workItemHandlers> <listeners> <ruleRuntimeEventListener type="org.domain.RuleRuntimeListener" /> <agendaEventListener type="org.domain.FirstAgendaListener" /> <agendaEventListener type="org.domain.SecondAgendaListener" /> <processEventListener type="org.domain.ProcessListener" /> </listeners> </ksession> </kbase> </kmodule>
This example defines two KIE bases. Two KIE sessions are instantiated from the
KBase1
KIE base, and one KIE session fromKBase2
. The KIE session fromKBase2
is astateless
KIE session, which means that data from a previous invocation of the KIE session (the previous session state) is discarded between session invocations. Specificpackages
of rule assets are included with both KIE bases. When you specify packages in this way, you must organize your DRL files in a folder structure that reflects the specified packages.After you create and save all DRL assets in your Java object, navigate to the
my-project
directory in the command line and run the following command to build your Java files. ReplaceRulesTest.java
with the name of your Java main class.javac -classpath "./dm-engine-jars/*:." RulesTest.java
If the build fails, address any problems described in the command line error messages and try again to validate the Java object until the object passes.
After your Java files build successfully, run the following command to execute the rules locally. Replace
RulesTest
with the prefix of your Java main class.java -classpath "./dm-engine-jars/*:." RulesTest
- Review the rules to ensure that they executed properly, and address any needed changes in the Java files.
To integrate the new rule assets with an existing project in Red Hat Decision Manager, you can compile the new Java project as a knowledge JAR (KJAR) and add it as a dependency in the pom.xml
file of the project in Business Central. To access the project pom.xml
file in Business Central, you can select any existing asset in the project and then in the Project Explorer menu on the left side of the screen, click the Customize View gear icon and select Repository View
20.2. Creating and executing DRL rules using Maven
You can use Maven archetypes to create DRL files with rules and integrate the archetypes with your Red Hat Decision Manager decision service. This method of creating DRL rules is helpful if you already use external Maven archetypes for your decision service and want to continue with the same workflow. If you do not already use this method, then the Business Central interface of Red Hat Decision Manager is recommended for creating DRL files and other rule assets.
Procedure
Navigate to a directory where you want to create a Maven archetype and run the following command:
mvn archetype:generate -DgroupId=com.sample.app -DartifactId=my-app -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false
This creates a directory
my-app
with the following structure:my-app |-- pom.xml `-- src |-- main | `-- java | `-- com | `-- sample | `-- app | `-- App.java `-- test `-- java `-- com `-- sample `-- app `-- AppTest.java
The
my-app
directory contains the following key components:-
A
src/main
directory for storing the application sources -
A
src/test
directory for storing the test sources -
A
pom.xml
file with the project configuration
-
A
Create a Java object on which the rule or rules will operate within the Maven archetype.
In this example, a
Person.java
file is created in the directorymy-app/src/main/java/com/sample/app
. ThePerson
class contains getter and setter methods to set and retrieve the first name, last name, hourly rate, and the wage of a person:package com.sample.app; public class Person { private String firstName; private String lastName; private Integer hourlyRate; private Integer wage; public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public Integer getHourlyRate() { return hourlyRate; } public void setHourlyRate(Integer hourlyRate) { this.hourlyRate = hourlyRate; } public Integer getWage(){ return wage; } public void setWage(Integer wage){ this.wage = wage; } }
Create a rule file in
.drl
format inmy-app/src/main/resources/com/sample/app
. The DRL file must contain at a minimum a package specification, an import list of data objects to be used by the rule or rules, and one or more rules withwhen
conditions andthen
actions.The following
Wage.drl
file contains aWage
rule that imports thePerson
class, calculates the wage and hourly rate values, and displays a message based on the result:package com.sample.app; import com.sample.app.Person; dialect "java" rule "Wage" when Person(hourlyRate * wage > 100) Person(name : firstName, surname : lastName) then System.out.println("Hello " + name + " " + surname + "!"); System.out.println("You are rich!"); end
In the
my-app/src/main/resources/META-INF
directory, create akmodule.xml
metadata file with the following content:<?xml version="1.0" encoding="UTF-8"?> <kmodule xmlns="http://www.drools.org/xsd/kmodule"> </kmodule>
This
kmodule.xml
file is a KIE module descriptor that selects resources to KIE bases and configures sessions. This file enables you to define and configure one or more KIE bases, and to include DRL files from specificpackages
in a specific KIE base. You can also create one or more KIE sessions from each KIE base.The following example shows a more advanced
kmodule.xml
file:<?xml version="1.0" encoding="UTF-8"?> <kmodule xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.drools.org/xsd/kmodule"> <kbase name="KBase1" default="true" eventProcessingMode="cloud" equalsBehavior="equality" declarativeAgenda="enabled" packages="org.domain.pkg1"> <ksession name="KSession1_1" type="stateful" default="true" /> <ksession name="KSession1_2" type="stateful" default="true" beliefSystem="jtms" /> </kbase> <kbase name="KBase2" default="false" eventProcessingMode="stream" equalsBehavior="equality" declarativeAgenda="enabled" packages="org.domain.pkg2, org.domain.pkg3" includes="KBase1"> <ksession name="KSession2_1" type="stateless" default="true" clockType="realtime"> <fileLogger file="debugInfo" threaded="true" interval="10" /> <workItemHandlers> <workItemHandler name="name" type="new org.domain.WorkItemHandler()" /> </workItemHandlers> <listeners> <ruleRuntimeEventListener type="org.domain.RuleRuntimeListener" /> <agendaEventListener type="org.domain.FirstAgendaListener" /> <agendaEventListener type="org.domain.SecondAgendaListener" /> <processEventListener type="org.domain.ProcessListener" /> </listeners> </ksession> </kbase> </kmodule>
This example defines two KIE bases. Two KIE sessions are instantiated from the
KBase1
KIE base, and one KIE session fromKBase2
. The KIE session fromKBase2
is astateless
KIE session, which means that data from a previous invocation of the KIE session (the previous session state) is discarded between session invocations. Specificpackages
of rule assets are included with both KIE bases. When you specify packages in this way, you must organize your DRL files in a folder structure that reflects the specified packages.In the
my-app/pom.xml
configuration file, specify the libraries that your application requires. Provide the Red Hat Decision Manager dependencies as well as thegroup ID
,artifact ID
, andversion
(GAV) of your application.<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.sample.app</groupId> <artifactId>my-app</artifactId> <version>1.0.0</version> <repositories> <repository> <id>jboss-ga-repository</id> <url>http://maven.repository.redhat.com/ga/</url> </repository> </repositories> <properties> <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target> </properties> <dependencies> <dependency> <groupId>org.drools</groupId> <artifactId>drools-compiler</artifactId> <version>VERSION</version> </dependency> <dependency> <groupId>org.drools</groupId> <artifactId>drools-mvel</artifactId> <version>VERSION</version> </dependency> <dependency> <groupId>org.kie</groupId> <artifactId>kie-api</artifactId> <version>VERSION</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> <scope>test</scope> </dependency> </dependencies> </project>
For information about Maven dependencies and the BOM (Bill of Materials) in Red Hat Decision Manager, see What is the mapping between Red Hat Decision Manager and Maven library version?.
-
Use the
testApp
method inmy-app/src/test/java/com/sample/app/AppTest.java
to test the rule. TheAppTest.java
file is created by Maven by default. In the
AppTest.java
file, add the requiredimport
statements to import KIE services, a KIE container, and a KIE session. Then load the KIE base, insert facts, and execute the rule from thetestApp()
method that passes the fact model to the rule.import org.kie.api.KieServices; import org.kie.api.runtime.KieContainer; import org.kie.api.runtime.KieSession; public void testApp() { // Load the KIE base: KieServices ks = KieServices.Factory.get(); KieContainer kContainer = ks.getKieClasspathContainer(); KieSession kSession = kContainer.newKieSession(); // Set up the fact model: Person p = new Person(); p.setWage(12); p.setFirstName("Tom"); p.setLastName("Summers"); p.setHourlyRate(10); // Insert the person into the session: kSession.insert(p); // Fire all rules: kSession.fireAllRules(); kSession.dispose(); }
After you create and save all DRL assets in your Maven archetype, navigate to the
my-app
directory in the command line and run the following command to build your files:mvn clean install
If the build fails, address any problems described in the command line error messages and try again to validate the files until the build is successful.
After your files build successfully, run the following command to execute the rules locally. Replace
com.sample.app
with your package name.mvn exec:java -Dexec.mainClass="com.sample.app.App"
- Review the rules to ensure that they executed properly, and address any needed changes in the files.
To integrate the new rule assets with an existing project in Red Hat Decision Manager, you can compile the new Maven project as a knowledge JAR (KJAR) and add it as a dependency in the pom.xml
file of the project in Business Central. To access the project pom.xml
file in Business Central, you can select any existing asset in the project and then in the Project Explorer menu on the left side of the screen, click the Customize View gear icon and select Repository View