Skip to main content

JVM

JVM binding

Status​

Planned. Development will begin after the Python binding stabilizes.

Timeline​

The JVM binding will target Java 22+ and Kotlin, following the Rust binding in priority.

Architecture​

The JVM binding will use the C FFI layer over the core crate, accessed via the Panama Foreign Function API (JEP 454, finalized in JDK 22).

Java / Kotlin application code
        |
        v
aster-jvm library             Idiomatic Java API: annotations,
                              CompletableFuture / Flow async model
        |
        | Panama Foreign Function API (JDK 22+)
        v
libaster.so / .dylib          C FFI shared library built from
                              the ffi/ crate
        |
        v
core crate (Rust)             Same backend as Python binding
        |
        v
iroh crates

Key design decisions​

  • Annotations will replace Python's decorators: @AsterService, @Rpc, @WireType("ns/Type").
  • Java records are the natural equivalent of Python dataclasses for wire types.
  • Apache Fory Java provides XLANG serialization, ensuring wire compatibility with the Python binding.
  • Async model will use CompletableFuture for unary calls and java.util.concurrent.Flow (Reactive Streams) for streaming patterns.
  • Panama FFI avoids JNI overhead and provides safer memory management for native calls.

Requirements​

  • JDK 22+ (for finalized Panama Foreign Function API).
  • The libaster native library for the target platform.

Further reading​