A plugin generator and safe abstraction for making Minecraft Bukkit Server Plugins in Rust using JNI.

(early prototype)

• Create a new Cargo library project (cargo new --lib)
• Add waterjet as dependency and build dependency
• Edit the project's Cargo.toml to include to following lines:

[package]
# ...
build = "build.rs"

[lib]
crate_type = ["cdylib"]

[package.metadata.waterjet]
name = "NameOfYourPluginsMainClass"

• Create a build script (build.rs in this example) which includes the following lines:

fn main() {
    waterjet::build::build();
}

• Add these lines to your src/lib.rs

use waterjet::{
    jni::{objects::GlobalRef, JNIEnv},
    McPlugin,
};

waterjet::hook!(NameOfYourPluginsMainClass, Model);

struct Model {}

impl Default for Model {
    fn default() -> Self {
        Model {}
    }
}

impl McPlugin for Model {
    fn on_enable(&self, _plugin: &GlobalRef, jni: &JNIEnv) {
        println!("Hello, World!");
    }

    fn on_disable(&self, _plugin: &GlobalRef, _jni: &JNIEnv) {
        println!("Bye, World!");
    }
}

• Build the project using cargo build
• Copy the generated .jar file from the target/$PROFILE folder into your server's plugins directory and the .so/.dll file into plugins/lib
• Start the server and you should see Hello, World! appear after the message indicating that [NameOfYourPluginsMainClass] version x.y.z was enabled

• The function waterjet::build::build parses your packages Cargo.toml for values under package.metadata.waterjet and converts them to a plugin.yml which is included in the generated JAR file. Supported keys include:

  Key	Default value	Hint
  name	camel-cased CARGO_PKG_NAME	single-line string
  authors	(CARGO_PKG_AUTHORS)	list or string
  website	(CARGO_PKG_HOMEPAGE)	single-line string
  description	(CARGO_PKG_DESCRIPTION)	optionally multi-line string
  version	(CARGO_PKG_VERSION)	single-line string
  api-version	1.13	single-line string
  prefix		single-line string
  loadbefore		list or string
  depend		list or string
  softdepend		list or string
  extra		multi-line string containing YAML

  Note: The extra key may be used for anything which should be appended to the generated plugin.yml (eg. permissions, commands)

  Note: For info on the keys supported by Spigot: https://www.spigotmc.org/wiki/plugin-yml/

• waterjet automatically generates a NameOfYourPluginsMainClass.jar file with all the necessary FFI code (currently onEnable and onDisable) which is linked to by the JVM against functions generated in the waterjet::hook proc-macro

• NameOfYourPluginsMainClass must be consistent across the Cargo.toml's value package.metadata.waterjet.name and the first argument supplied to the waterjet::hook proc-macro

• Generation of JAR containing plugin code which calls Rust code
• Automatic loading of Rust code from the plugin
• Compatibility with /reload command: Rust code is loaded by a custom classloader which is destructed in onDisable (see todo)
• Trait providing basic plugin methods (onEnable, onDisable) providing a reference to the JavaPlugin instance and to the JNIEnv

• Event handling
• Currently, the API is not on solid ground and must be redesigned for event handling, which would include rethinking the current threaded approach of the onEnable FFI function
• onDisable uses a System.gc() call to free the ClassLoader which loaded the plugin's Rust code, which may cause performance problems (quick and dirty solution to make /reload work)