{"id":3795,"date":"2025-11-24T10:00:04","date_gmt":"2025-11-24T15:00:04","guid":{"rendered":"https:\/\/www.mymiller.name\/wordpress\/?p=3795"},"modified":"2025-11-24T10:00:04","modified_gmt":"2025-11-24T15:00:04","slug":"evrete-a-modern-java-rule-engine","status":"publish","type":"post","link":"https:\/\/www.mymiller.name\/wordpress\/spring_ai\/evrete-a-modern-java-rule-engine\/","title":{"rendered":"EVRete: A Modern Java Rule Engine"},"content":{"rendered":"\n<div class=\"wp-block-jetpack-markdown\"><p>EVRete is a high-performance, lightweight, and open-source rule engine designed for Java applications. It offers a flexible and expressive way to implement rule-based logic, making it a compelling alternative to traditional rule engines like Drools. This article delves into EVRete\u2019s features, focusing on its annotation-based approach to rule definition.<\/p>\n<p><strong>Why EVRete?<\/strong><\/p>\n<p>EVRete stands out due to several key characteristics:<\/p>\n<ul>\n<li><strong>Speed and Efficiency:<\/strong> EVRete boasts impressive performance, often surpassing other rule engines in benchmarks. Its optimized implementation of the Rete algorithm ensures efficient rule evaluation.<\/li>\n<li><strong>Lightweight:<\/strong> With a small footprint, EVRete is easily integrated into various applications without significant overhead.<\/li>\n<li><strong>Expressive API:<\/strong> EVRete provides a fluent API and supports both lambda expressions and annotations for defining rules, catering to different coding styles.<\/li>\n<li><strong>Java-Centric:<\/strong>  Built purely in Java, EVRete seamlessly integrates with Java projects and leverages familiar language constructs.<\/li>\n<\/ul>\n<p><strong>Rule Definition with Annotations<\/strong><\/p>\n<p>EVRete\u2019s annotation-based approach provides a structured and organized way to define rules. Here\u2019s a breakdown of the key annotations:<\/p>\n<ul>\n<li><strong>@Rule:<\/strong> This annotation marks a method as a rule. It allows you to specify the rule\u2019s name and activation mode (e.g., <code>FIRE_ONCE<\/code>, <code>FIRE_EVERY_TIME<\/code>).<\/li>\n<li><strong>@Where:<\/strong> This annotation designates a method that defines the rule\u2019s condition. It evaluates to a boolean value, determining whether the rule should fire.<\/li>\n<li><strong>@Fact:<\/strong> This annotation is used to inject facts (data objects) into the rule method.<\/li>\n<\/ul>\n<p><strong>Example: Discount Rule<\/strong><\/p>\n<p>Let\u2019s illustrate with a classic discount rule:<\/p>\n<pre><code class=\"language-java\">import org.evrete.api.ActivationMode;\nimport org.evrete.dsl.annotation.Rule;\nimport org.evrete.dsl.annotation.Where;\n\npublic class DiscountRules {\n\n    @Rule(activationMode = ActivationMode.FIRE_EVERY_TIME)\n    public void applyDiscount(Order $order) {\n        $order.applyDiscount(0.1);\n    }\n\n    @Where\n    public boolean condition(Order $order) {\n        return $order.getTotalPrice() &gt; 100;\n    }\n}\n<\/code><\/pre>\n<p>In this example:<\/p>\n<ul>\n<li><code>applyDiscount<\/code> is marked as a rule that fires every time its condition is met.<\/li>\n<li><code>condition<\/code> defines the condition: the order\u2019s total price must exceed 100.<\/li>\n<li>The <code>Order<\/code> object is implicitly injected into both methods.<\/li>\n<\/ul>\n<p><strong>Integrating with Spring Boot<\/strong><\/p>\n<p>EVRete smoothly integrates with Spring Boot. Here\u2019s a basic service example:<\/p>\n<pre><code class=\"language-java\">import org.evrete.KnowledgeService;\nimport org.evrete.api.StatelessSession;\nimport org.springframework.stereotype.Service;\n\n@Service\npublic class OrderService {\n\n    private final KnowledgeService knowledgeService = new KnowledgeService();\n    private final StatelessSession session;\n\n    public OrderService() {\n        this.session = knowledgeService\n                .newStatelessSession()\n                .add(DiscountRules.class); \n    }\n\n    public Order applyRules(Order order) {\n        session.fire(order);\n        return order;\n    }\n}\n<\/code><\/pre>\n<p>This service creates a stateless session, adds the <code>DiscountRules<\/code> class, and fires the session with the provided <code>Order<\/code> object.<\/p>\n<p><strong>Benefits of Annotations<\/strong><\/p>\n<p>Using annotations offers several advantages:<\/p>\n<ul>\n<li><strong>Improved Readability:<\/strong> Annotations clearly separate rules and conditions, enhancing code organization.<\/li>\n<li><strong>Reduced Boilerplate:<\/strong> Annotations minimize the need for manual rule registration and configuration.<\/li>\n<li><strong>Type Safety:<\/strong> Annotations provide compile-time checks for rule parameters.<\/li>\n<\/ul>\n<p><strong>Beyond the Basics<\/strong><\/p>\n<p>EVRete provides a rich set of features beyond basic rule definitions:<\/p>\n<ul>\n<li><strong>Complex Event Processing (CEP):<\/strong>  Handle streams of events and detect patterns over time.<\/li>\n<li><strong>Type Declarations:<\/strong> Define custom data types and their properties for use in rules.<\/li>\n<li><strong>Stateful Sessions:<\/strong> Maintain session state between rule executions.<\/li>\n<\/ul>\n<p><strong>Conclusion<\/strong><\/p>\n<p>EVRete is a powerful and modern rule engine that empowers Java developers to implement complex logic in a clear and efficient manner. Its annotation-based approach further enhances its usability and maintainability. Whether you\u2019re building a simple rule-based system or a sophisticated event-driven application, EVRete offers a compelling toolkit for managing your business logic.<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":3791,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[443],"tags":[],"series":[],"class_list":["post-3795","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-spring_ai"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/10\/compliance-5899194_1280-jpg.avif","jetpack-related-posts":[{"id":3786,"url":"https:\/\/www.mymiller.name\/wordpress\/spring_ai\/integrating-easy-rules-with-a-spring-boot-microservice\/","url_meta":{"origin":3795,"position":0},"title":"Integrating Easy Rules with a Spring Boot Microservice","author":"Jeffery Miller","date":"December 24, 2025","format":false,"excerpt":"This post will walk you through integrating the lightweight and straightforward Easy Rules engine with your Spring Boot microservice. We'll cover the necessary dependencies, basic setup, and an example service to demonstrate its usage. 1. Project Setup and Dependencies Start by creating a Spring Boot project. Next, add the following\u2026","rel":"","context":"In &quot;Spring AI&quot;","block_context":{"text":"Spring AI","link":"https:\/\/www.mymiller.name\/wordpress\/category\/spring_ai\/"},"img":{"alt_text":"","src":"https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/10\/office-4249395_1280-jpg.avif","width":350,"height":200,"srcset":"https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/10\/office-4249395_1280-jpg.avif 1x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/10\/office-4249395_1280-jpg.avif 1.5x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/10\/office-4249395_1280-jpg.avif 2x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/10\/office-4249395_1280-jpg.avif 3x"},"classes":[]},{"id":3782,"url":"https:\/\/www.mymiller.name\/wordpress\/spring_ai\/integrating-rulebook-with-a-spring-boot-microservice\/","url_meta":{"origin":3795,"position":1},"title":"Integrating RuleBook with a Spring Boot Microservice","author":"Jeffery Miller","date":"December 24, 2025","format":false,"excerpt":"This post guides you through integrating the RuleBook rule engine with your Spring Boot microservice. We\u2019ll cover adding the dependency, configuring RuleBook, and creating a service to utilize it. 1. Project Setup and Dependency Start by creating a Spring Boot project. Next, add the RuleBook dependency to your pom.xml (Maven)\u2026","rel":"","context":"In &quot;Spring AI&quot;","block_context":{"text":"Spring AI","link":"https:\/\/www.mymiller.name\/wordpress\/category\/spring_ai\/"},"img":{"alt_text":"","src":"https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/10\/board-3772063_1280-jpg.avif","width":350,"height":200,"srcset":"https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/10\/board-3772063_1280-jpg.avif 1x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/10\/board-3772063_1280-jpg.avif 1.5x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/10\/board-3772063_1280-jpg.avif 2x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/10\/board-3772063_1280-jpg.avif 3x"},"classes":[]},{"id":3951,"url":"https:\/\/www.mymiller.name\/wordpress\/java\/scaling-streams-mastering-virtual-threads-in-spring-boot-4-and-java-25\/","url_meta":{"origin":3795,"position":2},"title":"Scaling Streams: Mastering Virtual Threads in Spring Boot 4 and Java 25","author":"Jeffery Miller","date":"December 22, 2025","format":false,"excerpt":"As a software architect, I\u2019ve seen the industry shift from heavy platform threads to reactive streams, and finally to the \"best of both worlds\": Virtual Threads. With the recent release of Spring Boot 4.0 and Java 25 (LTS), Project Loom's innovations have officially become the bedrock of high-concurrency enterprise Java.\u2026","rel":"","context":"In &quot;JAVA&quot;","block_context":{"text":"JAVA","link":"https:\/\/www.mymiller.name\/wordpress\/category\/java\/"},"img":{"alt_text":"","src":"https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2025\/12\/Gemini_Generated_Image_wqijejwqijejwqij-scaled.avif","width":350,"height":200,"srcset":"https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2025\/12\/Gemini_Generated_Image_wqijejwqijejwqij-scaled.avif 1x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2025\/12\/Gemini_Generated_Image_wqijejwqijejwqij-scaled.avif 1.5x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2025\/12\/Gemini_Generated_Image_wqijejwqijejwqij-scaled.avif 2x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2025\/12\/Gemini_Generated_Image_wqijejwqijejwqij-scaled.avif 3x"},"classes":[]},{"id":3970,"url":"https:\/\/www.mymiller.name\/wordpress\/architecture\/vibe-coding-the-next-generation-how-we-built-aimud-using-an-ai-ensemble\/","url_meta":{"origin":3795,"position":3},"title":"Vibe Coding the Next Generation: How We Built AIMUD Using an AI Ensemble","author":"Jeffery Miller","date":"April 21, 2026","format":false,"excerpt":"In the traditional world of software engineering, building a Multi-User Dungeon (MUD) is a rite of passage. It requires handling complex state, real-time networking, concurrency, and deep game logic. Usually, this takes months of meticulous, line-by-line keyboard grinding. But for AIMUD, we didn't just code; we vibe coded. By leveraging\u2026","rel":"","context":"In &quot;AI&quot;","block_context":{"text":"AI","link":"https:\/\/www.mymiller.name\/wordpress\/category\/ai\/"},"img":{"alt_text":"","src":"https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2026\/04\/Gemini_Generated_Image_6veptk6veptk6vep-scaled.avif","width":350,"height":200,"srcset":"https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2026\/04\/Gemini_Generated_Image_6veptk6veptk6vep-scaled.avif 1x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2026\/04\/Gemini_Generated_Image_6veptk6veptk6vep-scaled.avif 1.5x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2026\/04\/Gemini_Generated_Image_6veptk6veptk6vep-scaled.avif 2x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2026\/04\/Gemini_Generated_Image_6veptk6veptk6vep-scaled.avif 3x"},"classes":[]},{"id":3569,"url":"https:\/\/www.mymiller.name\/wordpress\/spring_ai\/integrating-prolog-with-spring-boot\/","url_meta":{"origin":3795,"position":4},"title":"Integrating Prolog with Spring Boot","author":"Jeffery Miller","date":"September 22, 2025","format":false,"excerpt":"Prolog, a declarative logic programming language, shines in solving specific types of problems that require knowledge representation and logical inference. Integrating Prolog with Spring Boot can bring the power of logic programming to your Java applications. 1. Setting Up Your Environment Add JPL Dependency: Include the Java Prolog Interface (JPL)\u2026","rel":"","context":"In &quot;Spring AI&quot;","block_context":{"text":"Spring AI","link":"https:\/\/www.mymiller.name\/wordpress\/category\/spring_ai\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/06\/Gemini_Generated_Image_avkkoeavkkoeavkk.jpg?fit=1200%2C1200&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/06\/Gemini_Generated_Image_avkkoeavkkoeavkk.jpg?fit=1200%2C1200&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/06\/Gemini_Generated_Image_avkkoeavkkoeavkk.jpg?fit=1200%2C1200&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/06\/Gemini_Generated_Image_avkkoeavkkoeavkk.jpg?fit=1200%2C1200&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2024\/06\/Gemini_Generated_Image_avkkoeavkkoeavkk.jpg?fit=1200%2C1200&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":3912,"url":"https:\/\/www.mymiller.name\/wordpress\/uncategorized\/spring-boot-4-0-whats-next-for-the-modern-java-architect\/","url_meta":{"origin":3795,"position":5},"title":"Spring Boot 4.0: What&#8217;s Next for the Modern Java Architect?","author":"Jeffery Miller","date":"September 24, 2025","format":false,"excerpt":"A Forward-Looking Comparison of Spring Boot 3.x and 4.0 Staying on top of the rapidly evolving Java ecosystem is paramount for any software architect. The shift from Spring Boot 2.x to 3.x brought significant changes, notably the move to Jakarta EE. Now, with the horizon of Spring Boot 4.0 and\u2026","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2025\/09\/per-2056740_1280.avif","width":350,"height":200,"srcset":"https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2025\/09\/per-2056740_1280.avif 1x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2025\/09\/per-2056740_1280.avif 1.5x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2025\/09\/per-2056740_1280.avif 2x, https:\/\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2025\/09\/per-2056740_1280.avif 3x"},"classes":[]}],"jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/posts\/3795","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/comments?post=3795"}],"version-history":[{"count":1,"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/posts\/3795\/revisions"}],"predecessor-version":[{"id":3796,"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/posts\/3795\/revisions\/3796"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/media\/3791"}],"wp:attachment":[{"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/media?parent=3795"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/categories?post=3795"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/tags?post=3795"},{"taxonomy":"series","embeddable":true,"href":"https:\/\/www.mymiller.name\/wordpress\/wp-json\/wp\/v2\/series?post=3795"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}