Jumper

Jumper is a scripting language for the JVM with the syntax of Java and the lightness of Lua.

import java.util.ArrayList;

dyn greet(name) { return "Hello, " + name; }

dyn names = new ArrayList();
names.add("Jumper");
names.add("Java");

dyn point = { x: 1, y: 2 };
for (dyn n : names) println(greet(n) + " " + (point.x + point.y));

• dyn for dynamic values, int, long, double, boolean, String where you want types checked
• functions, classes, lambdas, tables ({ x: 1 }), modules (import "utils.jmp";)
• Java classes used directly: import, new, method calls, fields
• an interpreter and a compiler to JVM bytecode for hot code

What it is for

Scripts inside a Java application: plugins and mods of a server, user automation, configs with logic.

• Embedding - a standard javax.script engine, the host passes its objects to scripts.
• Safety - every script runs under an access policy (.jma): which Java packages, classes and methods it may touch. Everything else is closed.
• Configs - .jmc files are a safe subset of the language: data, conditions, no loops or Java.
• Editors - IntelliJ IDEA, VS Code, Neovim.

How to add it

Requires Java 21+. Jumper is published through JitPack: Tag below is a release tag, the latest one is on the badge above.

Gradle (Kotlin)

repositories {
    mavenCentral()
    maven("https://jitpack.io")
}

dependencies {
    implementation("com.github.jumper-lang:jumper:Tag")
}

Gradle (Groovy)

repositories {
    mavenCentral()
    maven { url 'https://jitpack.io' }
}

dependencies {
    implementation 'com.github.jumper-lang:jumper:Tag'
}

Maven

<repositories>
    <repository>
        <id>jitpack.io</id>
        <url>https://jitpack.io</url>
    </repository>
</repositories>

<dependency>
    <groupId>com.github.jumper-lang</groupId>
    <artifactId>jumper</artifactId>
    <version>Tag</version>
</dependency>

Run a script from Java

ScriptEngine jumper = new ScriptEngineManager().getEngineByName("jumper");
jumper.put("name", "world");
jumper.eval("println(\"Hello, \" + name);");

Command line

Download jmp.jar from Releases:

java -jar jmp.jar script.jmp