java - JNI: NoSuchFieldError

Question

Output of: javap -s SomeClass

public org.someapp.SomeClass$_data data;
  Signature: Lorg/someapp/SomeClass$_data;

Definition of SomeClass in Java:

class SomeClass
{
    private class _data {
        byte[] something = new byte[1234];
    }

    public _data data;
}

Definition of native function in Java:

public static native int NativeFunction(SomeClass something);

Java implementation:

SomeClass x = new SomeClass();
NativeInterface.NativeFunction(x);

However, when the following code is executed:

JNIEXPORT jint JNICALL Java_org_someapp_NativeInterface_NativeFunction(JNIEnv* env, jobject obj, jobject someobject) {
    jclass some_class = (*env)->GetObjectClass(env, someobject);
    jfieldID data = (*env)->GetFieldID(env, some_class, "data", "Lorg/someapp/SomeClass$_data"); 
}

Java throws a "NoSuchFieldError;: data" exception on the GetFieldID call. I don't get it.. The signature is just fine (copied straight from javap).

Note that getting the field ID for a simpler variable, like an unsigned short (with signature "S") works just fine.

Answer 1

I have a feeling that "Lorg/someapp/SomeClass$_data" should be "Lorg/someapp/SomeClass$_data;". Note the semicolon.