Function JNI_OnLoad

src/java/jni/convert.cpp:114–156

Called by JVM when it loads our library.

// Called by JVM when it loads our library.
JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* jvm, void* reserved)
{
  // Grab the context ClassLoader of the current thread, if any.
  JNIEnv* env;
  if (jvm->GetEnv(JNIENV_CAST(&env), JNI_VERSION_1_2) != JNI_OK) {
    return JNI_ERR; // JNI version not supported.
  }

  // Find thread's context class loader.
  jclass javaLangThread = env->FindClass("java/lang/Thread");
  assert(javaLangThread != nullptr);

  jclass javaLangClassLoader = env->FindClass("java/lang/ClassLoader");
  assert(javaLangClassLoader != nullptr);

  jmethodID currentThread = env->GetStaticMethodID(
      javaLangThread, "currentThread", "()Ljava/lang/Thread;");
  assert(currentThread != nullptr);

  jmethodID getContextClassLoader = env->GetMethodID(
      javaLangThread, "getContextClassLoader", "()Ljava/lang/ClassLoader;");
  assert(getContextClassLoader != nullptr);

  jobject thread = env->CallStaticObjectMethod(javaLangThread, currentThread);
  assert(thread != nullptr);

  jobject classLoader = env->CallObjectMethod(thread, getContextClassLoader);

  if (classLoader != nullptr) {
    mesosClassLoader = env->NewWeakGlobalRef(classLoader);
  }

  // Set the 'loaded' property so we don't try and load it again. This
  // is necessary because a native library can be loaded either with
  // 'System.load' or 'System.loadLibrary' and while redundant calls
  // to 'System.loadLibrary' will be ignored one call of each could
  // cause an error.
  jclass clazz = FindMesosClass(env, "org/apache/mesos/MesosNativeLibrary");
  jfieldID loaded = env->GetStaticFieldID(clazz, "loaded", "Z");
  env->SetStaticBooleanField(clazz, loaded, (jboolean) true);

  return JNI_VERSION_1_2;
}


// Called by JVM when it unloads our library.