[JAVA-14177] Renamed rule-engines to rule-enfines-modules (#12723)

Co-authored-by: panagiotiskakos <[email protected]>

rule-engines-modules/README.md

@@ -0,0 +1,7 @@
+## Rule Engines Modules
+
+This module contains articles about rule engines. Articles specific to a given rule engine go in the relevant submodule.
+
+### Relevant articles:
+
+- [List of Rules Engines in Java](https://www.baeldung.com/java-rule-engines)

rule-engines-modules/easy-rules/pom.xml

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+<?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.baeldung.easyrules</groupId>
+    <artifactId>easy-rules</artifactId>
+    <version>1.0</version>
+    <name>easy-rules</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>rule-engines-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.jeasy</groupId>
+            <artifactId>easy-rules-core</artifactId>
+            <version>${easy-rules.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <easy-rules.version>3.0.0</easy-rules.version>
+    </properties>
+
+</project>

rule-engines-modules/easy-rules/src/main/java/com/baeldung/easyrules/HelloWorldRule.java

@@ -0,0 +1,20 @@
+package com.baeldung.easyrules;
+
+import org.jeasy.rules.annotation.Action;
+import org.jeasy.rules.annotation.Condition;
+import org.jeasy.rules.annotation.Rule;
+
+@Rule(name = "Hello World rule", description = "Always say hello world")
+public class HelloWorldRule {
+
+    @Condition
+    public boolean when() {
+        return true;
+    }
+
+    @Action
+    public void then() throws Exception {
+        System.out.println("hello world");
+    }
+
+}

rule-engines-modules/easy-rules/src/main/java/com/baeldung/easyrules/Launcher.java

@@ -0,0 +1,21 @@
+package com.baeldung.easyrules;
+
+import org.jeasy.rules.api.Facts;
+import org.jeasy.rules.api.Rules;
+import org.jeasy.rules.api.RulesEngine;
+import org.jeasy.rules.core.DefaultRulesEngine;
+
+public class Launcher {
+    public static void main(String... args) {
+        // create facts
+        Facts facts = new Facts();
+
+        // create rules
+        Rules rules = new Rules();
+        rules.register(new HelloWorldRule());
+
+        // create a rules engine and fire rules on known facts
+        RulesEngine rulesEngine = new DefaultRulesEngine();
+        rulesEngine.fire(rules, facts);
+    }
+}

rule-engines-modules/easy-rules/src/main/resources/logback.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

rule-engines-modules/evrete/README.md

@@ -0,0 +1,3 @@
+## Relevant Articles:
+
+- [Introduction to the Evrete Rule Engine](https://www.baeldung.com/java-evrete-rule-engine)

rule-engines-modules/evrete/pom.xml

@@ -0,0 +1,36 @@
+<?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.baeldung.evrete</groupId>
+    <artifactId>evrete</artifactId>
+    <version>1.0</version>
+    <name>evrete</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>rule-engines-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <!-- Core library -->
+        <dependency>
+            <groupId>org.evrete</groupId>
+            <artifactId>evrete-core</artifactId>
+            <version>${evrete.version}</version>
+        </dependency>
+        <!-- Annotated Java classes -->
+        <dependency>
+            <groupId>org.evrete</groupId>
+            <artifactId>evrete-dsl-java</artifactId>
+            <version>${evrete.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <evrete.version>2.1.04</evrete.version>
+    </properties>
+
+</project>

rule-engines-modules/evrete/src/main/java/com/baeldung/evrete/introduction/IntroductionAJR.java

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+package com.baeldung.evrete.introduction;
+
+import com.baeldung.evrete.introduction.model.Customer;
+import com.baeldung.evrete.introduction.model.Invoice;
+import org.evrete.KnowledgeService;
+import org.evrete.api.Knowledge;
+
+import java.io.IOException;
+import java.net.URL;
+import java.util.*;
+
+public class IntroductionAJR {
+    public static void main(String[] args) throws IOException {
+        ClassLoader classLoader = IntroductionAJR.class.getClassLoader();
+        KnowledgeService service = new KnowledgeService();
+        URL rulesetUrl = classLoader.getResource("rules/SalesRuleset.java");
+        Knowledge knowledge = service.newKnowledge(
+            "JAVA-SOURCE",
+            rulesetUrl
+        );
+
+        List<Customer> customers = Arrays.asList(
+            new Customer("Customer A"),
+            new Customer("Customer B"),
+            new Customer("Customer C")
+        );
+
+        Random random = new Random();
+        Collection<Object> sessionData = new LinkedList<>(customers);
+        for (int i = 0; i < 100_000; i++) {
+            Customer randomCustomer = customers.get(random.nextInt(customers.size()));
+            Invoice invoice = new Invoice(randomCustomer, 100 * random.nextDouble());
+            sessionData.add(invoice);
+        }
+
+        knowledge
+            .newStatelessSession()
+            .insert(sessionData)
+            .fire();
+
+        for (Customer c : customers) {
+            System.out.printf("%s:\t$%,.2f%n", c.getName(), c.getTotal());
+        }
+
+        service.shutdown();
+    }
+}

rule-engines-modules/evrete/src/main/java/com/baeldung/evrete/introduction/IntroductionInline.java

@@ -0,0 +1,58 @@
+package com.baeldung.evrete.introduction;
+
+import org.evrete.KnowledgeService;
+import org.evrete.api.Knowledge;
+import com.baeldung.evrete.introduction.model.*;
+
+import java.util.*;
+
+public class IntroductionInline {
+    public static void main(String[] args) {
+        KnowledgeService service = new KnowledgeService();
+        Knowledge knowledge = service
+            .newKnowledge()
+            .newRule("Clear total sales")
+            .forEach("$c", Customer.class)
+            .execute(ctx -> {
+                Customer c = ctx.get("$c");
+                c.setTotal(0.0);
+            })
+            .newRule("Compute totals")
+            .forEach(
+                    "$c", Customer.class,
+                    "$i", Invoice.class
+            )
+            .where("$i.customer == $c")
+            .execute(ctx -> {
+                Customer c = ctx.get("$c");
+                Invoice i = ctx.get("$i");
+                c.addToTotal(i.getAmount());
+            });
+
+
+        List<Customer> customers = Arrays.asList(
+            new Customer("Customer A"),
+            new Customer("Customer B"),
+            new Customer("Customer C")
+        );
+
+        Random random = new Random();
+        Collection<Object> sessionData = new LinkedList<>(customers);
+        for (int i = 0; i < 100_000; i++) {
+            Customer randomCustomer = customers.get(random.nextInt(customers.size()));
+            Invoice invoice = new Invoice(randomCustomer, 100 * random.nextDouble());
+            sessionData.add(invoice);
+        }
+
+        knowledge
+            .newStatelessSession()
+            .insert(sessionData)
+            .fire();
+
+        for (Customer c : customers) {
+            System.out.printf("%s:\t$%,.2f%n", c.getName(), c.getTotal());
+        }
+
+        service.shutdown();
+    }
+}

rule-engines-modules/evrete/src/main/java/com/baeldung/evrete/introduction/model/Customer.java

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+package com.baeldung.evrete.introduction.model;
+
+public class Customer {
+    private double total = 0.0;
+    private final String name;
+
+    public Customer(String name) {
+        this.name = name;
+    }
+
+    public void addToTotal(double amount) {
+        this.total += amount;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public double getTotal() {
+        return total;
+    }
+
+    public void setTotal(double total) {
+        this.total = total;
+    }
+}

rule-engines-modules/evrete/src/main/java/com/baeldung/evrete/introduction/model/Invoice.java

@@ -0,0 +1,19 @@
+package com.baeldung.evrete.introduction.model;
+
+public class Invoice {
+    private final Customer customer;
+    private final double amount;
+
+    public Invoice(Customer customer, double amount) {
+        this.customer = customer;
+        this.amount = amount;
+    }
+
+    public Customer getCustomer() {
+        return customer;
+    }
+
+    public double getAmount() {
+        return amount;
+    }
+}

rule-engines-modules/evrete/src/main/resources/logback.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

rule-engines-modules/evrete/src/main/resources/rules/SalesRuleset.java

@@ -0,0 +1,20 @@
+package org.abc.author1;
+
+import com.baeldung.evrete.introduction.model.Customer;
+import com.baeldung.evrete.introduction.model.Invoice;
+import org.evrete.dsl.annotation.Rule;
+import org.evrete.dsl.annotation.Where;
+
+public class SalesRuleset {
+
+    @Rule
+    public void rule1(Customer $c) {
+        $c.setTotal(0.0);
+    }
+
+    @Rule
+    @Where("$i.customer == $c")
+    public void rule2(Customer $c, Invoice $i) {
+        $c.addToTotal($i.getAmount());
+    }
+}

rule-engines-modules/evrete/src/test/java/com/baeldung/evrete/introduction/IntroductionAJRUnitTest.java

@@ -0,0 +1,80 @@
+package com.baeldung.evrete.introduction;
+
+import com.baeldung.evrete.introduction.model.Customer;
+import com.baeldung.evrete.introduction.model.Invoice;
+import org.evrete.KnowledgeService;
+import org.evrete.api.Knowledge;
+import org.evrete.api.RuleSession;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import java.io.IOException;
+import java.util.*;
+
+class IntroductionAJRUnitTest {
+    private static KnowledgeService service;
+
+    @BeforeAll
+    static void setUpClass() {
+        service = new KnowledgeService();
+    }
+
+    @AfterAll
+    static void shutDownClass() {
+        service.shutdown();
+    }
+
+    /**
+     * This test makes sure that each customer's actual total sales is equal to the amount
+     * computed by the rule engine
+     */
+    @ParameterizedTest
+    @ValueSource(strings = {"true", "false"})
+    void sessionTotalsTest(String type) throws IOException  {
+        boolean stateful = Boolean.parseBoolean(type);
+        ClassLoader classLoader = IntroductionAJR.class.getClassLoader();
+        KnowledgeService service = new KnowledgeService();
+        Knowledge knowledge = service
+            .newKnowledge(
+                "JAVA-SOURCE",
+                classLoader.getResource("rules/SalesRuleset.java")
+            );
+
+
+        List<Customer> customers = Arrays.asList(
+            new Customer("Customer A"),
+            new Customer("Customer B"),
+            new Customer("Customer C")
+        );
+        Collection<Object> sessionData = new LinkedList<>(customers);
+
+        HashMap<Customer, Double> actualTotals = new HashMap<>();
+        Random random = new Random();
+        for (int i = 0; i < 1_000; i++) {
+            Customer randomCustomer = customers.get(random.nextInt(customers.size()));
+            Invoice invoice = new Invoice(randomCustomer, random.nextInt(100));
+            sessionData.add(invoice);
+
+            Double d = actualTotals.get(randomCustomer);
+            if(d == null) {
+                d = 0.0;
+            }
+            d = d + invoice.getAmount();
+            actualTotals.put(randomCustomer, d);
+        }
+
+        RuleSession<?> session = stateful ? knowledge.newStatefulSession() : knowledge.newStatelessSession();
+        session
+            .insert(sessionData)
+            .fire();
+
+        for(Customer c : customers) {
+            double d1 = c.getTotal();
+            double d2 = actualTotals.get(c);
+            assert d1 == d2;
+        }
+
+    }
+}

rule-engines-modules/evrete/src/test/java/com/baeldung/evrete/introduction/IntroductionInlineUnitTest.java

@@ -0,0 +1,90 @@
+package com.baeldung.evrete.introduction;
+
+import com.baeldung.evrete.introduction.model.Customer;
+import com.baeldung.evrete.introduction.model.Invoice;
+import org.evrete.KnowledgeService;
+import org.evrete.api.Knowledge;
+import org.evrete.api.RuleSession;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import java.util.*;
+
+class IntroductionInlineUnitTest {
+    private static KnowledgeService service;
+
+    @BeforeAll
+    static void setUpClass() {
+        service = new KnowledgeService();
+    }
+
+    @AfterAll
+    static void shutDownClass() {
+        service.shutdown();
+    }
+
+    /**
+     * This test makes sure that each customer's actual total sales is equal to the amount
+     * computed by the rule engine
+     */
+    @ParameterizedTest
+    @ValueSource(strings = {"true", "false"})
+    void sessionTotalsTest(String type) {
+        boolean stateful = Boolean.parseBoolean(type);
+        Knowledge knowledge = service
+            .newKnowledge()
+            .newRule("Clear customer's total sales")
+            .forEach("$c", Customer.class)
+            .execute(ctx -> {
+                Customer c = ctx.get("$c");
+                c.setTotal(0.0);
+            })
+            .newRule("Compute totals")
+            .forEach(
+                    "$c", Customer.class,
+                    "$i", Invoice.class
+            )
+            .where("$i.customer == $c")
+            .execute(ctx -> {
+                Customer c = ctx.get("$c");
+                Invoice i = ctx.get("$i");
+                c.addToTotal(i.getAmount());
+            });
+
+
+        List<Customer> customers = Arrays.asList(
+            new Customer("Customer A"),
+            new Customer("Customer B"),
+            new Customer("Customer C")
+        );
+        Collection<Object> sessionData = new LinkedList<>(customers);
+
+        HashMap<Customer, Double> actualTotals = new HashMap<>();
+        Random random = new Random();
+        for (int i = 0; i < 1_000; i++) {
+            Customer randomCustomer = customers.get(random.nextInt(customers.size()));
+            Invoice invoice = new Invoice(randomCustomer, random.nextInt(100));
+            sessionData.add(invoice);
+
+            Double d = actualTotals.get(randomCustomer);
+            if(d == null) {
+                d = 0.0;
+            }
+            d = d + invoice.getAmount();
+            actualTotals.put(randomCustomer, d);
+        }
+
+        RuleSession<?> session = stateful ? knowledge.newStatefulSession() : knowledge.newStatelessSession();
+        session
+            .insert(sessionData)
+            .fire();
+
+        for(Customer c : customers) {
+            double d1 = c.getTotal();
+            double d2 = actualTotals.get(c);
+            assert d1 == d2;
+        }
+    }
+}

rule-engines-modules/jess/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Jess Rule Engine and JSR 94](https://www.baeldung.com/java-rule-engine-jess-jsr-94)

rule-engines-modules/jess/pom.xml

@@ -0,0 +1,30 @@
+<?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.baeldung.rules.jess</groupId>
+    <artifactId>jess</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <dependencies>
+        <dependency>
+            <groupId>jsr94</groupId>
+            <artifactId>jsr94</artifactId>
+            <version>1.1</version>
+        </dependency>
+        <!-- the below be available after we download and unpack jess.jar and mvn install it into our 
+            local m2, compile errors with this project would go away then <dependency> <groupId>gov.sandia</groupId> 
+            <artifactId>jess</artifactId> <version>7.1p2</version> </dependency> -->
+    </dependencies>
+
+    <!-- include repository http://dist.wso2.org/maven2 for jsr94 -->
+    <repositories>
+        <repository>
+            <id>wso2</id>
+            <name>Numerical Method's Maven Repository</name>
+            <url>http://dist.wso2.org/maven2/</url>
+        </repository>
+    </repositories>
+
+</project>

rule-engines-modules/jess/src/main/java/com/baeldung/rules/jess/JessHello.java

@@ -0,0 +1,17 @@
+package com.baeldung.rules.jess;
+
+import jess.JessException;
+import jess.Rete;
+
+public class JessHello {
+    public static final String RULES_FILE = "helloJess.clp";
+
+    public static void main(String[] args) throws JessException {
+        Rete engine = new Rete();
+        engine.reset();
+
+        engine.batch(RULES_FILE);
+
+        engine.run();
+    }
+}

rule-engines-modules/jess/src/main/java/com/baeldung/rules/jess/JessWithData.java

@@ -0,0 +1,42 @@
+package com.baeldung.rules.jess;
+
+import com.baeldung.rules.jess.model.Answer;
+import com.baeldung.rules.jess.model.Question;
+import jess.Filter;
+import jess.JessException;
+import jess.Rete;
+
+import java.util.Iterator;
+import java.util.logging.Logger;
+
+public class JessWithData {
+    public static final String RULES_BONUS_FILE = "bonus.clp";
+    private static Logger log = Logger.getLogger("JessWithData");
+
+    public static void main(String[] args) throws JessException {
+        Rete engine = new Rete();
+        engine.reset();
+
+        engine.batch(RULES_BONUS_FILE);
+
+        prepareData(engine);
+
+        engine.run();
+
+        checkResults(engine);
+    }
+
+    private static void checkResults(Rete engine) {
+        Iterator results = engine.getObjects(new Filter.ByClass(Answer.class));
+        while (results.hasNext()) {
+            Answer answer = (Answer) results.next();
+            log.info(answer.toString());
+        }
+    }
+
+    private static void prepareData(Rete engine) throws JessException {
+        Question question = new Question("Can I have a bonus?", -5);
+        log.info(question.toString());
+        engine.add(question);
+    }
+}

rule-engines-modules/jess/src/main/java/com/baeldung/rules/jess/JessWithJsr94.java

@@ -0,0 +1,98 @@
+package com.baeldung.rules.jess;
+
+import com.baeldung.rules.jess.model.Answer;
+import com.baeldung.rules.jess.model.Question;
+
+import javax.rules.*;
+import javax.rules.admin.RuleAdministrator;
+import javax.rules.admin.RuleExecutionSet;
+import javax.rules.admin.RuleExecutionSetCreateException;
+import javax.rules.admin.RuleExecutionSetRegisterException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.rmi.RemoteException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.logging.Logger;
+
+public class JessWithJsr94 {
+    public static final String RULES_BONUS_FILE = "/bonus.clp";
+    public static final String RULES_URI = "com/baeldung/rules/bonus";
+    private static final String RULE_SERVICE_PROVIDER = "jess.jsr94";
+    private static Logger log = Logger.getLogger("JessWithData");
+
+    public static void main(String[] args) throws Exception {
+        RuleServiceProvider ruleServiceProvider = instantiateJessInstance();
+
+        // load our rules and register them with the rules provider
+        registerRules(RULES_BONUS_FILE, RULES_URI, ruleServiceProvider);
+
+        runRules(RULES_URI, ruleServiceProvider);
+    }
+
+    private static RuleServiceProvider instantiateJessInstance() throws ClassNotFoundException, ConfigurationException {
+        // Load the rule service provider of the reference implementation.
+        // Loading this class will automatically register this provider with the provider manager.
+        Class.forName(RULE_SERVICE_PROVIDER + ".RuleServiceProviderImpl");
+
+        //  Get the rule service provider from the provider manager.
+        return RuleServiceProviderManager.getRuleServiceProvider(RULE_SERVICE_PROVIDER);
+    }
+
+    private static void runRules(String rulesURI, RuleServiceProvider ruleServiceProvider)
+      throws ConfigurationException, RuleSessionTypeUnsupportedException, RuleSessionCreateException, RuleExecutionSetNotFoundException, RemoteException, InvalidRuleSessionException {
+        // Get a RuleRuntime and invoke the rule engine.
+        RuleRuntime ruleRuntime = ruleServiceProvider.getRuleRuntime();
+
+        //Create a statelessRuleSession.
+        StatelessRuleSession statelessRuleSession = (StatelessRuleSession) ruleRuntime.createRuleSession(rulesURI, new HashMap(), RuleRuntime.STATELESS_SESSION_TYPE);
+
+        calculateResults(statelessRuleSession);
+
+        statelessRuleSession.release();
+    }
+
+    private static void calculateResults(StatelessRuleSession statelessRuleSession) throws InvalidRuleSessionException, RemoteException {
+        List data = prepareData();
+
+        // execute the rules
+        List results = statelessRuleSession.executeRules(data);
+
+        checkResults(results);
+    }
+
+    private static List prepareData() {
+        List data = new ArrayList();
+        data.add(new Question("Can I have a bonus?", -5));
+        return data;
+    }
+
+    private static void checkResults(List results) {
+        Iterator itr = results.iterator();
+        while (itr.hasNext()) {
+            Object obj = itr.next();
+            if (obj instanceof Answer) {
+                log.info(obj.toString());
+            }
+        }
+    }
+
+    private static void registerRules(String rulesFile, String rulesURI, RuleServiceProvider serviceProvider) throws ConfigurationException, RuleExecutionSetCreateException, IOException, RuleExecutionSetRegisterException {
+        //  Get the rule administrator.
+        RuleAdministrator ruleAdministrator = serviceProvider.getRuleAdministrator();
+
+        // load the rules
+        InputStream ruleInput = JessWithJsr94.class.getResourceAsStream(rulesFile);
+        HashMap vendorProperties = new HashMap();
+
+        // Create the RuleExecutionSet
+        RuleExecutionSet ruleExecutionSet = ruleAdministrator
+          .getLocalRuleExecutionSetProvider(vendorProperties)
+          .createRuleExecutionSet(ruleInput, vendorProperties);
+
+        // Register the rule execution set.
+        ruleAdministrator.registerRuleExecutionSet(rulesURI, ruleExecutionSet, vendorProperties);
+    }
+}

rule-engines-modules/jess/src/main/java/com/baeldung/rules/jess/model/Answer.java

@@ -0,0 +1,31 @@
+package com.baeldung.rules.jess.model;
+
+public class Answer {
+    private String answer;
+    private int newBalance;
+
+    public Answer(String answer, int newBalance) {
+        this.answer = answer;
+        this.newBalance = newBalance;
+    }
+
+    public int getNewBalance() {
+        return newBalance;
+    }
+
+    public void setNewBalance(int newBalance) {
+        this.newBalance = newBalance;
+    }
+
+    public String getAnswer() {
+        return answer;
+    }
+
+    public void setAnswer(String answer) {
+        this.answer = answer;
+    }
+
+    public String toString() {
+        return "Answer(answer=" + answer + ", newBalance=" + newBalance + ")";
+    }
+}

rule-engines-modules/jess/src/main/java/com/baeldung/rules/jess/model/Question.java

@@ -0,0 +1,32 @@
+package com.baeldung.rules.jess.model;
+
+public class Question {
+    private String question;
+    private int balance;
+
+    public Question(String question, int balance) {
+        this.question = question;
+        this.balance = balance;
+    }
+
+    public String getQuestion() {
+        return question;
+    }
+
+    public void setQuestion(String question) {
+        this.question = question;
+    }
+
+    public int getBalance() {
+        return balance;
+    }
+
+    public void setBalance(int balance) {
+        this.balance = balance;
+    }
+
+    public String toString() {
+        return "Question(question=" + question + ", balance=" + balance + ")";
+    }
+
+}

rule-engines-modules/jess/src/main/resources/bonus.clp

@@ -0,0 +1,8 @@
+(import com.baeldung.rules.jess.model.*)
+(deftemplate Question       (declare (from-class Question)))
+(deftemplate Answer       (declare (from-class Answer)))
+
+(defrule avoid-overdraft "Give $50 to anyone overdrawn"
+    ?q <- (Question { balance < 0 })
+    =>
+    (add (new Answer "Overdrawn bonus" (+ ?q.balance 50))))

rule-engines-modules/jess/src/main/resources/helloJess.clp

@@ -0,0 +1,3 @@
+;; Hello, world in Jess!
+
+(printout t "Hello from Jess!" crlf)

rule-engines-modules/openl-tablets/pom.xml

@@ -0,0 +1,34 @@
+<?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.baeldung.openltablets</groupId>
+    <artifactId>openl-tablets</artifactId>
+    <version>1.0</version>
+    <name>openl-tablets</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>rule-engines-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.openl</groupId>
+            <artifactId>org.openl.core</artifactId>
+            <version>${openl.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openl.rules</groupId>
+            <artifactId>org.openl.rules</artifactId>
+            <version>${openl.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <openl.version>5.19.4</openl.version>
+    </properties>
+
+</project>

rule-engines-modules/openl-tablets/src/main/java/com/baeldung/openltablets/model/Case.java

@@ -0,0 +1,23 @@
+package com.baeldung.openltablets.model;
+
+public class Case {
+
+    private User user;
+    private int hourOfDay;
+
+    public User getUser() {
+        return user;
+    }
+
+    public void setUser(final User user) {
+        this.user = user;
+    }
+
+    public int getHourOfDay() {
+        return hourOfDay;
+    }
+
+    public void setHourOfDay(final int hourOfDay) {
+        this.hourOfDay = hourOfDay;
+    }
+}

rule-engines-modules/openl-tablets/src/main/java/com/baeldung/openltablets/model/Greeting.java

@@ -0,0 +1,20 @@
+package com.baeldung.openltablets.model;
+
+public enum Greeting {
+
+    GOOD_MORNING("Good Morning"),
+    GOOD_AFTERNOON("Good Afternoon"),
+    GOOD_EVENING("Good Evening"),
+    GOOD_NIGHT("Good Night");
+
+    private final String literal;
+
+    private Greeting(final String literal) {
+        this.literal = literal;
+    }
+
+    public String getLiteral() {
+        return literal;
+    }
+
+}

rule-engines-modules/openl-tablets/src/main/java/com/baeldung/openltablets/model/User.java

@@ -0,0 +1,14 @@
+package com.baeldung.openltablets.model;
+
+public class User {
+
+    private String name;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(final String name) {
+        this.name = name;
+    }
+}

rule-engines-modules/openl-tablets/src/main/java/com/baeldung/openltablets/rules/IRule.java

@@ -0,0 +1,7 @@
+package com.baeldung.openltablets.rules;
+
+import com.baeldung.openltablets.model.Case;
+
+public interface IRule {
+    void helloUser(final Case aCase, final Response response);
+}

rule-engines-modules/openl-tablets/src/main/java/com/baeldung/openltablets/rules/Main.java

@@ -0,0 +1,31 @@
+package com.baeldung.openltablets.rules;
+
+
+import java.time.LocalDateTime;
+
+import org.openl.rules.runtime.RulesEngineFactory;
+import org.openl.runtime.EngineFactory;
+
+import com.baeldung.openltablets.model.Case;
+import com.baeldung.openltablets.model.User;
+
+public class Main {
+    private IRule instance;
+
+    public static void main(String[] args) {
+        Main rules = new Main();
+        User user = new User();
+        user.setName("Donald Duck");
+        Case aCase = new Case();
+        aCase.setUser(user);
+        aCase.setHourOfDay(23);
+        rules.process(aCase);
+    }
+
+    public void process(Case aCase) {
+        final EngineFactory<IRule> engineFactory = new RulesEngineFactory<IRule>(getClass().getClassLoader()
+            .getResource("openltablets/HelloUser.xls"), IRule.class);
+        instance = engineFactory.newEngineInstance();
+        instance.helloUser(aCase, new Response());
+    }
+}