Java HotSpot Virtual Machine

I have a jar that I can execute normally using java.exe Trying to execute this jar from a JNI-using C++ project I hit error after error.

Configuration:

WIndows 8
Visual Studio 2017
Netbeans 8.2
JRE/JDK: jdk1.8.0_102
JVM dll path: C:/Program Files/Java/jdk1.8.0_102/jre/bin/server/jvm.dll

In the C project I load the java project as a binary stream, then loop each class entry and use DefineClass( name, null, bytes, size ), five classes fail.

Upon retryng the five, four pass ( so, dependency problem ), one class never passes.

failing class:

import javax.mail.Authenticator;
import javax.mail.PasswordAuthentication;
public class MyAuthenticator extends Authenticator
{
    String username;
    String password;
    public MyAuthenticator( String u , String p )
    {
        this.username = u;
        this.password = p;
    }
    @Override
    public PasswordAuthentication getPasswordAuthentication()
    {
        return new PasswordAuthentication( username, password );
    }
}

If I use FindClass in the C project for Authenticator and PasswordAuthentication, they pass. Java project still get class not found.

If I use class for name in the java project it fails, it passes if I also send the system class loader (default loader is null), but the java project still cant find the class once it gets to the code that calls new.

I also have five custom threads started on the main of the java project, they also complain about class not found (for every thread) eg for Thread1 extends Thread, if I do new Thread1() and Thread1.run() it will not be able to. These Thread classes pass the DefineClass loop so they should exist on the jvm.

Im gtting frustrated, but what am I doing wrong? or is JNI too simple to do this?