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Graal Languages

1 Introduction

Micronaut Graal Languages is a collection of components for integration of Graal based dynamic languages with Micronaut Framework.

Note: Micronaut React server-side rendering, which is based on GraalJS, is part of Micronaut Views.

2 Release History

For this project, you can find a list of releases (with release notes) here:

https://github.com/micronaut-projects/micronaut-graal-languages/releases

3 GraalPy

Micronaut GraalPy is an annotation-based feature to expose Python modules as Java Beans.

3.1 Getting Started

To use the GraalPy integration:

1) Add the micronaut-graalpy dependency on your classpath:

implementation("io.micronaut.micronaut-graal-languages:micronaut-graalpy")

<dependency>
    <groupId>io.micronaut.micronaut-graal-languages</groupId>
    <artifactId>micronaut-graalpy</artifactId>
</dependency>

2) Add the GraalPy plugin configuration for your build tool

2a) GraalPy Maven plugin

pom.xml

<build>
 <plugins>
  <plugin>
    <groupId>org.graalvm.python</groupId>
    <artifactId>graalpy-maven-plugin</artifactId>
    <version>${graalpy.version}</version>
    <executions>
      <execution>
        <configuration>
          <packages>
            <package>termcolor==2.2</package> <!-- (1) -->
          </packages>
        </configuration>
      </execution>
    </executions>
  </plugin>
 </plugins>
 <!-- ... -->

2b) GraalPy Gradle plugin

build.gradle

plugins {
    ...
    id("org.graalvm.python") version "24.2.0"
}

graalPy {
    packages = ["termcolor==2.2"] // (1)
}

Optional list of Python Package Index (PyPI) packages to be automatically installed during the build.

3) Add the dealer.py Python script to the resources folder. The location follows the convention recognized by the GraalPy support library.

src/main/resources/org.graalvm.python.vfs/src/dealer.py

import random
def shuffle(data):
    random.shuffle(data)
    return data

4) Create a Java interface for the Python module

import io.micronaut.graal.graalpy.annotations.GraalPyModule;

@GraalPyModule("dealer")  // (1)
public interface DealerService {
    Object[] shuffle(Object[] cards); // (2)
}

Use GraalPyModule annotation to map this interface to a Python module. The value of the annotation is the name of the Python module that should be used.
Methods in the interface will be automatically mapped to Python functions of the same name. The mapping follows the polyglot type mapping rules.

5) This library will provide an injectable implementation of the interface backed by the Python module.

import io.micronaut.context.annotation.Bean;
import jakarta.inject.Inject;

@Bean
public class DocExample {
    @Inject DealerService dealerService;

    public Object[] play() {
        Object[] cards = new Object[] { 1, 2, 3 };
        cards = dealerService.shuffle(cards);
        // ...
        return cards;
    }
}

Note	See GraalPyModule documentation for more details about global state, threading, and limitations.

4 Repository

You can find the source code of this project in this repository:

https://github.com/micronaut-projects/micronaut-graal-languages