Evrete

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Important!

Check out what's new in version 4.0.0 and read the migration guides at https://www.evrete.org/docs#migration-guide

Evrete is a forward-chaining Java rule engine that implements the RETE algorithm and is fully compliant with the Java Rule Engine specification (JSR 94).

Historically designed as a fast and lightweight alternative to full-scale rule management systems, the engine also brings its own mix of features:

Rule authoring

Rules can be authored both externally and inline as a plain Java 8 code.
The engine allows rules to be authored as annotated Java sources, classes, or archives.
The library itself is a flexible tool for creating custom domain-specific rule languages (DSL).

Intuitive and developer-friendly

Library's type system allows it to seamlessly process any kinds of objects, including JSON and XML.
Fluent builders, Java functional interfaces, and other best practices keep developers' code concise and clear.
Key components are exposed as Service Provider Interfaces and can be customized.

Performance and security

The engine's algorithm and memory are optimized for large-scale and labeled data.
Built-in support of Java Security Manager protects against unwanted or potentially malicious code in the rules.

Project home

The official project description, documentation, and usage examples can be found at https://www.evrete.org

Prerequisites

Evrete is Java 8+ compatible and ships with zero dependencies.

Installation

Maven:


<dependency>
    <groupId>org.evrete</groupId>
    <artifactId>evrete-core</artifactId>
    <version>4.0.3</version>
</dependency>

Gradle:

implementation 'org.evrete:evrete-core:4.0.3'

Support for annotated rules (optional)

Maven:


<dependency>
    <groupId>org.evrete</groupId>
    <artifactId>evrete-dsl-java</artifactId>
    <version>4.0.3</version>
</dependency>

Gradle:

implementation 'org.evrete:evrete-dsl-java:4.0.3'

Quick start

Below is a simple example of rule that removes from session memory every integer except prime numbers.

As inline Java code:

public class PrimeNumbersInline {
    public static void main(String[] args) {
        KnowledgeService service = new KnowledgeService();
        Knowledge knowledge = service
                .newKnowledge()
                .builder()
                .newRule("prime numbers")
                .forEach(
                        "$i1", Integer.class,
                        "$i2", Integer.class,
                        "$i3", Integer.class
                )
                .where("$i1 * $i2 == $i3")
                .execute(ctx -> ctx.deleteFact("$i3"))
                .build();

        try (StatefulSession session = knowledge.newStatefulSession()) {
            // Inject candidates
            for (int i = 2; i <= 100; i++) {
                session.insert(i);
            }

            // Execute rules
            session.fire();

            // Print current memory state
            session.forEachFact((handle, o) -> System.out.println(o));
        }
        service.shutdown();
    }
}

As annotated Java source file:

public class PrimeNumbersDSLUrl {
    public static void main(String[] args) {
        KnowledgeService service = new KnowledgeService();
        Knowledge knowledge = service
                .newKnowledge()
                .importRules(
                        "JAVA-SOURCE",
                        URI.create("https://www.evrete.org/examples/PrimeNumbersSource.java").toURL());

        try (StatefulSession session = knowledge.newStatefulSession()) {
            // Inject candidates
            for (int i = 2; i <= 100; i++) {
                session.insert(i);
            }
            // Execute rules
            session.fire();
            // Printout current memory state
            session.forEachFact((handle, o) -> System.out.println(o));
        }
    }
}

where the rule itself is stored externally as PrimeNumbersSource.java

For further details see the official documentation

License

This project uses the following license: MIT