BAEL-5143 (#11273)

* BAEL-5143

* Modified as per PR comments

* The List<> type for session data is changed to a more generic Collection<>

* Version upgrade

Co-authored-by: 0swald <andrey.bichkevskiy@gmail.com>

rule-engines/evrete/pom.xml

@@ -0,0 +1,35 @@
+<?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>
+
+    <properties>
+        <evrete.version>2.1.04</evrete.version>
+    </properties>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>rule-engines</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>
+</project>

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

@@ -0,0 +1,47 @@
+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/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/evrete/src/main/java/com/baeldung/evrete/introduction/model/Customer.java

@@ -0,0 +1,26 @@
+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/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/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/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/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/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/pom.xml

@@ -15,6 +15,7 @@
 
     <modules>
         <module>easy-rules</module>
+        <module>evrete</module>
         <module>openl-tablets</module>
         <module>rulebook</module>
         <!-- <module>jess</module> --> <!-- requires dependencies which are not publicly available -->