Julia for Java binding

This is initial Java binding implementation. For now there are supported only basic functions for running scripts and types converting.

See https://docs.julialang.org/en/stable/manual/embedding/

Class org.julia.jni.swig.Julia4J implements JNI calls to libjulia. See example

Classes from package class org.julia.scripting implement jsr233 scripting interface. See example

Examples

Example 1:

import org.julia.jni.swig.Julia4J;

Julia4J.jl_init();
Julia4J.jl_eval_string("dump(:(1 + 2x^2))");
Julia4J.jl_atexit_hook(0);

Example 2:

import org.julia.jni.swig.Julia4J;
import org.julia.jni.swig.SWIGTYPE_p_jl_value_t;
import org.julia.scripting.JuliaScriptEngineFactory;

ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("julia");

// evaluate Julia code
engine.eval("dump(:(x^2 + y^2))");

Object result = engine.eval("2 ^ 10");
long checkedResult = Julia4J.jl_unbox_int64((SWIGTYPE_p_jl_value_t) result);
assertEquals(1024, checkedResult);

Example 3:

import org.julia.jni.swig.Julia4J;
import org.julia.jni.swig.SWIGTYPE_p_jl_value_t;
import org.julia.scripting.JuliaScriptEngineFactory;

ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("julia");

engine.put("x", "hello");
// print global variable "x"
engine.eval("println(x);");
// the above line prints "hello"

// Now, pass a different script context
ScriptContext newContext = new SimpleScriptContext();
Bindings engineScope = newContext.getBindings(ScriptContext.ENGINE_SCOPE);

// add new variable "x" to the new engineScope
engineScope.put("x", "world");

// execute the same script - but this time pass a different script context
engine.eval("println(x);", newContext);
// the above line prints "world"

// example from https://docs.oracle.com/javase/7/docs/technotes/guides/scripting/programmer_guide/

Prerequisites

For running: julia should be installed.

For building with binaries: julia, julia-devel, Java 8, swig, gcc, make.

How to build

These sources doesn't include native binary libraries. But you can build them manually by swig/build.sh script. Also see swig/lib_src/Makefile

Next run ./gradlew build

TODO

• automate native binaries building. For now, added CMake. Mac OS works with manual copy only due to rpath issue. Linux platform might be working but with running make install after build.sh from swig/ path. And proper environment variables setup is also required both for JDK and Julia.
• fix SWIG related class names like SWIGTYPE_p_jl_value_t
• implement convenient Java<->julia_JNI types converters
• implement all methods of scripting engine/factory instead of stubs
• implement direct access to functions and variable of Julia context to avoid code parsing per call
• ...