JNI, The Java Native Interface
 
Standard programming interface for writing Java native methods and embedding the Java virtual machine into native applications.

Website: http://download.oracle.com/javase/6/docs/technotes/guides/jni/index.html, http://java.sun.com/docs/books/jni/
Platforms supported: Win32, Linux
Headers to include: jni.bi
Header version: from 2006
Examples: in examples/other-languages/Java/

Example


Three files:

  • mylib.bas - A DLL writting in FreeBASIC

#include "jni.bi"
    
'' Note: The mangling must be "windows-ms" or the JRE won't find any function
Extern "windows-ms"
    Function Java_MyLib_add( env As JNIEnv Ptr, obj As jobject, l As jint, r As jint ) As jint Export
        Return l + r
    End Function
End Extern


  • Mylib.java - The Java class that represents the interface to the FreeBASIC code and ensures the FreeBASIC DLL is loaded

(cpp)
class MyLib {
	public native int add( int l, int r );
	static {
		System.loadLibrary( "mylib" );
	}
}

  • Test.java - The Java main() that uses the Mylib class

(cpp)
class Test {
	public static void main(String[] args) {
		MyLib lib = new MyLib();
		System.out.println( "2+2=" + lib.add( 2, 2 ) ); 
	}
}

Steps to test it:

  • Compile the FreeBASIC DLL: fbc mylib.bas -dll
  • Compile the two Java classes: javac Mylib.java Test.java
  • Run the Test class: java Test