We build the Python interpreter into a java application using the Panama project

A couple of days ago I saw Brian Goetz's tweet, but only today my hands reached around to play with examples. About this and I want to briefly tell. About the Panama project on Habré already wrote , therefore I will just show couple of simple examples of how it is possible to apply native binder .

First of all, you will need a C compiler. If you are using Linux or MacOS, then you already have it. If Windows, you have to first install Build Tools for Visual Studio 2017 . And, of course, you need OpenJDK with Panama support. You can get it either by assembling the “foreign” branch of the corresponding repository , or by downloading an Early-Access build .

Let's start with a minimal example - a simple function that adds two numbers:

adder.h

#ifndef _ADDER_H#define _ADDER_H
__declspec(dllexport) intadd(int, int);
#endif

adder.c

#include"adder.h"
__declspec(dllexport)
intadd(int a, int b){
    return a + b;
}

Example.java

// импорт jextract'нутых "заголовочных" классовimportstatic com.example.adder_h.*;
publicclassExample{
    publicstaticvoidmain(String[] args){
        System.out.println(add(3, 5));
    }
}

We compile in DLL

cl /LD adder.c

We use the utility jextractto generate a java interface based on the header file:

jextract -L . -l adder -o adder.jar -t "com.example" adder.h

And we use the resulting jar file to build and run java code:

javac -cp adder.jar Example.java
java -cp .;adder.jar Example

While not particularly impressive, but allows you to understand the principle. Now try using python37.dll.

PythonMain.java

import java.foreign.Libraries;
import java.foreign.Scope;
import java.foreign.memory.Pointer;
importstatic org.python.Python_h.*;
importstatic org.python.pylifecycle_h.*;
importstatic org.python.pythonrun_h.*;
publicclassPythonMain{
    publicstaticvoidmain(String[] args){
        Py_Initialize();
        try (Scope s = Scope.newNativeScope()) {
            PyRun_SimpleStringFlags(s.allocateCString(
                "print(sum([33, 55, 66]))\n"),
                Pointer.nullPointer());
        }
        Py_Finalize();
    }
}

We generate interfaces:

jextract -L "C:\Python37" -l python37 -o python.jar -t "org.python" --record-library-path C:\Python37\include\Python.h

Compile and run:

javac -cp python.jar PythonMain.java
java -cp .;python.jar PythonMain

Congratulations, your java-application has just loaded the Python interpreter into itself and executed the script in it!

More examples can be found in the instructions for pioneers .

Tags:

We build the Python interpreter into a java application using the Panama project

Also popular now: