Best way to return an array of values from c++?

Question

I have a a group of structs made of a mix of primitive types in c++. I need to return these to Java but Im not sure the best way to return them quickly.
Should I create a class corresponding to the structure in Java then create the class in C++ and set its fields and return that? Or should I create arrays of different primitive types and return those? Can I even do that? Say, store a group of arrays of different types in a jobjectArray and return that? If I can, what would be the return type? Object[][]?

Answer 1

Java side:
package jni;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
* @author Ian Schneider
public class Struct {
    static {
        System.loadLibrary("struct");
    public static void doit() {
        ByteBuffer bytes = ByteBuffer.allocateDirect(structSize());
        bytes.order(ByteOrder.nativeOrder());
        getData(bytes);
        System.out.println("int : " + bytes.getInt());
        System.out.println("double : " + bytes.getDouble());
    private static native void getData(ByteBuffer bytes);
    private static native int structSize();
    public static void main(String[] args) throws Exception {
        doit();
}C side (I'm not a C programmer, so be nice):
#include "jni_Struct.h"
struct foo {
  int x;
  double y;
} foo;
JNIEXPORT void JNICALL Java_jni_Struct_getData
  (JNIEnv * env, jobject obj, jobject buf) {
  struct foo * f = (void*) malloc(sizeof(foo));
  f->x = 123;
  f->y = 456.;
  void * data = (void *) (*env)->GetDirectBufferAddress(env,buf);
  memcpy(data,f,sizeof(foo));
  free(f);
JNIEXPORT jint JNICALL Java_jni_Struct_structSize
  (JNIEnv * env, jobject obj) {
  return sizeof(foo);
}This is a bit simplistic as foo is static in size (no pointers), but hopefully you get the point.