BAEL-1258 Added example code for Jess and JSR94 (#9693)

* BAEL-1258 Added example code for Jess and JSR94

* BAEL-1258 Relocate to rule-modules

* BAEL-1258 Remove README as per PR review

* šBAEL-1258 Declared exceptions and replace System.out.println with log statements

* BAEL-1258 Removed Lombok

* BAEL-1258 Removed Lombok

* BAEL-1258 Rename artifactId to match directory name

rule-engines/jess/pom.xml

@@ -0,0 +1,25 @@
+<?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>
+
+    <!-- https://mvnrepository.com/artifact/jsr94/jsr94 -->
+    <dependencies>
+        <dependency>
+            <groupId>jsr94</groupId>
+            <artifactId>jsr94</artifactId>
+            <version>1.1</version>
+        </dependency>
+        <dependency>
+            <groupId>gov.sandia</groupId>
+            <artifactId>jess</artifactId>
+            <version>7.1p2</version>
+        </dependency>
+    </dependencies>
+
+</project>

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

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+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/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/jess/src/main/java/com/baeldung/rules/jess/JessWithJsr94.java

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+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/jess/src/main/java/com/baeldung/rules/jess/model/Answer.java

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+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/jess/src/main/java/com/baeldung/rules/jess/model/Question.java

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+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/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/jess/src/main/resources/helloJess.clp

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