Crate javawithrust

Transfer function calls between Rust and Java in a rust-like (ish) way.

Features

• Call static java functions from rust.
• Call associated rust functions from java.
• Convert java objects to rust structs.

Limitations

• Can not call java methods from rust.
• Can not call rust methods from java.
• Can only convert the following rust types to java objects:
  • String
  • i8
  • i16
  • i32
  • i64
  • f32
  • f64

Examples

// Rust
 
use javawithrust::prelude::*;
 
#[jclass(io.example.CustomJavaClass)]
pub struct CustomRustStruct;
 
#[jfuncs]
impl CustomRustStruct {
 
    fn hello() { // Will return `Result<(), String>`
        println!("hello");
        CustomRustStruct::world()?;
        return Ok(());
    }
 
    // Will call `io.example.CustomJavaClass.world()`.
    fn world();
 
    // Callable from java.
    fn sum(a : i32, b : i32) -> i32 { // Will return `Result<i32, String>`
        return Ok(a + b);
    }
 
}

// Java
 
package io.example;
 
import org.astonbitecode.j4rs.api.Instance;
import org.astonbitecode.j4rs.api.java2rust.Java2RustUtils;
 
public class CustomJavaClass
{
    // Load the dynamic library.
    // The library is loaded from the same directory as the jar.
    static {
        String os=System.getProperty("os.name").toLowerCase();String path=J2RS.class.getProtectionDomain().getCodeSource().getLocation().getPath();path=path.substring(0,path.lastIndexOf("/")).replaceAll("%20"," ")+"/"+
        "robot"; // Name of the dynamic library file. `.so` and `.dll` are added automatically.
        if (os.contains("linux") || os.contains("unix") || os.contains("android")) {
            path += ".so";
        } else if (os.contains("win")) {
            path += ".dll";
        }
        else {throw new UnsatisfiedLinkError("Can not load dynamic library in unknown operating system `" + os + "`");}
        System.load(path);
    }
 
    public static native void hello();
 
    public static void world() {
        System.out.println("world!");
    }
 
    private static native Instance<Integer> sum(Instance<Integer> i1, Instance<Integer> i2);
    public static Integer sumFromRust(Integer a, Integer b) {
        // Convert the objects.
        return Java2RustUtils.getObjectCasted(J2RS.sum(
            Java2RustUtils.createInstance(a),
            Java2RustUtils.createInstance(b)
        ));
    }
 
}

Modules

prelude

Pulls in all required objects and types.

Attribute Macros

call_from_java_expand

INTERNAL

jclass

Define a Java class.

jfuncs

Define static Java class functions to bind.