Using JNI method in SWIG's input file

Sometimes we've to use JNI's built in methods in SWIG's input file. Though SWIG's proxy class can do everything possible for JNI,but I prefer to use JNI's method where SWIG gets complicated. For example, I have a byte Array in my java file.If I want to retrieve the array by pinning, we can use getArrayPrimitiveCritical(

) JNI method.Here I gonna give an example that will help you a lot about using JNI's built in method in SWIG.

Let the java file is Runner.java and the code is:


public class Runner {
static {
try {
System.loadLibrary("sample");
}
catch (UnsatisfiedLinkError e) {

System.err.println("Native code library failed to load.\n" + e);
System.exit(1);
}
}



public static void main(String argv[]) {
//declaration of the array
byte array[] = new byte [10000];
for (int i = 0; i <>
array[i] = (byte)((int)i%64);

//call the native method

sample.point_accessPinArray(array);
}
}


Now the input file can be like this(sample.i)

/* File : sample.i */

%module sample
%{
#include "ByteArray.h"
#include "/usr/lib/jvm/java-6-openjdk/include/jni.h"

JNIEXPORT void JNICALL Java_sampleJNI_point_1accessPinArray(JNIEnv *jenv, jclass jcls,jbyteArray array) {

int i;int size;
size = (*jenv)->GetArrayLength(jenv, array);
//pinning process is going to be started from here if your garbage collector supports //pinning.

jbyte* body = (*jenv)->GetPrimitiveArrayCritical(jenv, array, NULL);

(*jenv)->ReleasePrimitiveArrayCritical(jenv, array, body, 0);
}
%}
%native(point_accessPinArray) void *point_accessPinArray(jbyteArray array);



Commands to compile and run:

$swig -java sample.i
$gcc -c -fpic sample_wrap.cxx -I/usr/lib/jvm/java-6-openjdk/include/ -I/usr/lib/jvm/java-6-openjdk/include/linux/
$gcc -shared sample_wrap.o -o libexample.so
$export LD_LIBRARY_PATH=.:$LD_LIBRARY_PATH
$javac Runner.java
$java Runner

Using SWIG to cooperate Java with C++

Courtesy : SWIG Tutorial

Let the main file where my functions and variables are located is example.cxx
Write that source.

Then create an interface file .let example.i
where the previous module's variables and functions have to be declared.

Sample:


/* example.i */
%module example
%{
/* Put header files here or function declarations like below */
extern type variableName;
extern type functionName(parameters);
%}

extern type variableName;
extern type functionName(parameters);
//end of file



Then create main java file.Let Its name is main.java


//main.java
public class main {
public static void main(String argv[]) {
System.loadLibrary("exampl

e");
System.out.println(example.getvariableName());
System.out.println(example.functionName(parameters));

}
}



commands:
$swig -c++ -java example.i
$g++ -c -fpic example.cxx
$g++ -c -fpic example_wrap.cxx -I/usr/lib/jvm/java-6-sun-1.6.0.06/include/ -I/usr/lib/jvm/java-6-sun-1.6.0.06/include/linux
$g++ -shared example.o example_wrap.o -o libexample.so
$export LD_LIBRARY_PATH=.:$LD_LIBRARY_PATH
$javac main.java
$java main


You can make a shell script to automate the commands.