diff --git a/drools/backward-chaining/src/main/java/com/baeldung/drools/BackwardChaining.java b/drools/backward-chaining/src/main/java/com/baeldung/drools/BackwardChaining.java new file mode 100644 index 0000000000..1c1d258b47 --- /dev/null +++ b/drools/backward-chaining/src/main/java/com/baeldung/drools/BackwardChaining.java @@ -0,0 +1,33 @@ +package com.baeldung.drools; + +import org.kie.api.KieServices; +import org.kie.api.runtime.KieContainer; +import org.kie.api.runtime.KieSession; + +import com.baeldung.drools.model.Fact; +import com.baeldung.drools.model.Result; + +public class BackwardChaining { + public static void main(String[] args) { + Result result = new BackwardChaining().backwardChaining(); + System.out.println(result.getValue()); + result.getFacts().stream().forEach(System.out::println); + } + + public Result backwardChaining() { + Result result = new Result(); + KieServices ks = KieServices.Factory.get(); + KieContainer kContainer = ks.getKieClasspathContainer(); + KieSession ksession = kContainer.newKieSession("ksession-backward-chaining"); + ksession.setGlobal("result", result); + ksession.insert(new Fact("Asia", "Planet Earth")); +// ksession.insert(new Fact("China", "Asia")); + ksession.insert(new Fact("Great Wall of China", "China")); + + ksession.fireAllRules(); + + return result; + + } + +} \ No newline at end of file diff --git a/drools/backward-chaining/src/main/java/com/baeldung/drools/model/Fact.java b/drools/backward-chaining/src/main/java/com/baeldung/drools/model/Fact.java new file mode 100644 index 0000000000..62b44b9d92 --- /dev/null +++ b/drools/backward-chaining/src/main/java/com/baeldung/drools/model/Fact.java @@ -0,0 +1,69 @@ +package com.baeldung.drools.model; + +import org.kie.api.definition.type.Position; + +public class Fact { + + @Position(0) + private String element; + + @Position(1) + private String place; + + public Fact(String element, String place) { + this.element = element; + this.place = place; + } + + public String getElement() { + return element; + } + + public void setElement(String element) { + this.element = element; + } + + public String getPlace() { + return place; + } + + public void setPlace(String place) { + this.place = place; + } + + @Override + public int hashCode() { + final int prime = 31; + int result = 1; + result = prime * result + ((element == null) ? 0 : element.hashCode()); + result = prime * result + ((place == null) ? 0 : place.hashCode()); + return result; + } + + @Override + public boolean equals(Object obj) { + if (this == obj) + return true; + if (obj == null) + return false; + if (getClass() != obj.getClass()) + return false; + Fact other = (Fact) obj; + if (element == null) { + if (other.element != null) + return false; + } else if (!element.equals(other.element)) + return false; + if (place == null) { + if (other.place != null) + return false; + } else if (!place.equals(other.place)) + return false; + return true; + } + + @Override + public String toString() { + return "Fact{" + "element='" + element + '\'' + ", place='" + place + '\'' + '}'; + } +} \ No newline at end of file diff --git a/drools/backward-chaining/src/main/java/com/baeldung/drools/model/Result.java b/drools/backward-chaining/src/main/java/com/baeldung/drools/model/Result.java new file mode 100644 index 0000000000..b22557832b --- /dev/null +++ b/drools/backward-chaining/src/main/java/com/baeldung/drools/model/Result.java @@ -0,0 +1,31 @@ +package com.baeldung.drools.model; + +import java.util.ArrayList; +import java.util.List; + +public class Result { + private String value; + private List facts = new ArrayList<>(); + + public String getValue() { + return value; + } + + public void setValue(String value) { + this.value = value; + } + + public List getFacts() { + return facts; + } + + public void setFacts(List facts) { + this.facts = facts; + } + + public void addFact(String fact) { + this.facts.add(fact); + } + + +} diff --git a/drools/backward-chaining/src/main/resources/META-INF/maven/pom.properties b/drools/backward-chaining/src/main/resources/META-INF/maven/pom.properties new file mode 100644 index 0000000000..26d8331732 --- /dev/null +++ b/drools/backward-chaining/src/main/resources/META-INF/maven/pom.properties @@ -0,0 +1,3 @@ +groupId=com.baeldung.drools +artifactId=DroosBackwardChaining +version=1.0.0-SNAPSHOT diff --git a/drools/backward-chaining/src/main/resources/backward_chaining/rules.drl b/drools/backward-chaining/src/main/resources/backward_chaining/rules.drl new file mode 100644 index 0000000000..abcf95b9f1 --- /dev/null +++ b/drools/backward-chaining/src/main/resources/backward_chaining/rules.drl @@ -0,0 +1,34 @@ +package com.baeldung + +import com.baeldung.drools.model.Fact; + +global com.baeldung.drools.model.Result result; + +dialect "mvel" + +query belongsTo(String x, String y) + Fact(x, y;) + or + (Fact(z, y;) and belongsTo(x, z;)) +end + +rule "Great Wall of China BELONGS TO Planet Earth" +when + belongsTo("Great Wall of China", "Planet Earth";) +then + result.setValue("Decision one taken: Great Wall of China BELONGS TO Planet Earth"); +end + +rule "Great Wall of China DOES NOT BELONG TO of Planet Earth" +when + not belongsTo("Great Wall of China", "Planet Earth";) +then + result.setValue("Decision two taken: Great Wall of China DOES NOT BELONG TO Planet Earth"); +end + +rule "print all facts" +when + belongsTo(element, place;) +then + result.addFact(element + " IS ELEMENT OF " + place); +end diff --git a/drools/backward-chaining/src/test/java/com/baeldung/test/BackwardChainingTest.java b/drools/backward-chaining/src/test/java/com/baeldung/test/BackwardChainingTest.java new file mode 100644 index 0000000000..676e941950 --- /dev/null +++ b/drools/backward-chaining/src/test/java/com/baeldung/test/BackwardChainingTest.java @@ -0,0 +1,57 @@ +package com.baeldung.test; + +import org.junit.Before; +import org.junit.Test; +import org.junit.runner.RunWith; +import org.junit.runners.JUnit4; +import org.kie.api.KieServices; +import org.kie.api.runtime.KieContainer; +import org.kie.api.runtime.KieSession; + +import com.baeldung.drools.model.Fact; +import com.baeldung.drools.model.Result; + +import static junit.framework.TestCase.assertEquals; + +@RunWith(value = JUnit4.class) +public class BackwardChainingTest { + private Result result; + private KieServices ks; + private KieContainer kContainer; + private KieSession ksession; + + @Before + public void before() { + result = new Result(); + ks = KieServices.Factory.get(); + kContainer = ks.getKieClasspathContainer(); + ksession = kContainer.newKieSession("ksession-backward-chaining"); + ksession.setGlobal("result", result); + } + + @Test + public void whenWallOfChinaIsGiven_ThenItBelongsToPlanetEarth() { + + ksession.setGlobal("result", result); + ksession.insert(new Fact("Asia", "Planet Earth")); + ksession.insert(new Fact("China", "Asia")); + ksession.insert(new Fact("Great Wall of China", "China")); + + ksession.fireAllRules(); + + // Assert Decision one + assertEquals(result.getValue(), "Decision one taken: Great Wall of China BELONGS TO Planet Earth"); + } + + @Test + public void whenChinaIsNotGiven_ThenWallOfChinaDoesNotBelongToPlanetEarth() { + ksession.insert(new Fact("Asia", "Planet Earth")); + // ksession.insert(new Location("China", "Asia")); // not provided to force Decision two + ksession.insert(new Fact("Great Wall of China", "China")); + + ksession.fireAllRules(); + + // Assert Decision two + assertEquals(result.getValue(), "Decision two taken: Great Wall of China DOES NOT BELONG TO Planet Earth"); + } +}