Java Plugin

java-plugin is a client-side implementation of go-plugin. You can use it to run plugins written in Go (or any language, but Go is best supported) from a JVM application.

Usage

Let's say you have a Java (or Kotlin, or Groovy) interface. You'd like to be able to implement that interface in Go rather than in a JVM language. You can use java-plugin!

Imagine your interface is a simple Counter:

interface Counter {
  fun put(key: String, value: Long, adder: (a: Long, b: Long) -> Long)
  fun get(key: String): Long
}

When put-ing a new value with a Counter, you can pass an adder lambda implementation that maps the old value into a new value to be stored.

If you have a binary that implements this interface, you can fetch a Counter like so:

val manager = Manager()
val client = manager.start(
  ClientConfig(
    handshakeConfig = HandshakeConfig(
      magicCookieKey = "key",
      magicCookieValue = "value",
      protocolVersion = 1
    ),
    cmd = listOf("./path/to/plugin/binary"),
    plugins = listOf(CounterPlugin())
  )
)

// This Counter looks like a normal Java interface!
val counter = client.dispense<Counter>()

counter.put("key", 10) { a, b ->
  println("adding $a + $b")
  a + b
}

For more implementation guidance, see the Examples.

Features

java-plugin implements many of go-plugin's features:

• Bidirectional communication
• Complex arguments and return values
• Protocol versioning
• Logging and stdout/stderr syncing
• Automatic mTLS

java-plugin supports plugins communicating via gRPC over Unix domain sockets. It does not support Go's net/rpc protocol or communication over localhost.

java-plugin is tested on macos-latest and ubuntu-latest.

Examples

The *-example directories contain complete, runnable plugin examples. Be sure to clone this repo with its submodules:

git clone git@github.com:danielpeach/java-plugin.git --recurse-submodules

If you're trying to run the examples from Intellij, please remember to run the buildGo gradle task beforehand.

Bugs

Automatic mTLS does not work for plugins using bidirectional communication. This is a bug in the server-side framework.