CODEWITHSUNDEEP
javac++java-native-interface
İbrahim
İbrahim

Reputation: 1021

JNI: Class not found or FindClass returns NULL

I'm trying JNI with C++. But I get this error: Class not found!. I searched other solved, but not working for me.
Code.java:

package com.xxx;

public class Code
{
  public void getMessage()
  {
    System.out.println("Hello World!");
  }
}

main.cpp:

#include <jni.h>
#include <iostream>
using namespace std;

int main(int argc, char* argv[])
{
  JavaVM* jvm;
  JNIEnv* env;
  JavaVMInitArgs jvm_args;
  JavaVMOption options[1];

  options[0].optionString = "-Djava.class.path=myclasses";
  jvm_args.version = JNI_VERSION_1_2;
  jvm_args.options = options;
  jvm_args.nOptions = 1;
  jvm_args.ignoreUnrecognized = JNI_TRUE;

  jint res = JNI_CreateJavaVM(&jvm, (void**)&env, &jvm_args);
  if (res < 0)
  {
    cout << "Cannot create JVM!\n";
    exit(1);
  }

  jclass class_ = env->FindClass("com/xxx/Code");
  if (class_ == 0)
  {
    cout << "Code class not found!\n";
    exit(1);
  }

  jmethodID method_id = env->GetMethodID(class_, "getMessage", "()V");
  if (method_id == 0)
  {
    cout << "getMessage() method not found!\n";
    exit(1);
  }

  env->CallVoidMethod(class_, method_id);

  return 0;
}

Directory for my files:
Directory

I tried -Djava.class.path=myclasses/com/xxx and env->FindClass("Code");. Also I tried -Djava.class.path=myclasses and env->FindClass("com/xxx/Code");. But both not working. What is reason of Code class not found! message?

Upvotes: 2

Views: 4263

Answers (1)

Wheezil
Wheezil

Reputation: 3462

I initially put this in a comment, but poster indicates it is the solution.

Your code assumes that "myclasses" is a folder under the CWD of your C++ program. While the directory structure looks correct, this won't work unless the CWD is the parent of "myclasses". Try printing the return of getcwd() and see where you are

Upvotes: 2

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