C++ ClassLoader implementation via JNI??

Question

Ok, I've gotten so far that I can read a .jar file into memory (as a .zip file), I've implemented my own FindClass that extracts the .class from .zip (in memory) and passes the code bytes to JNI's DefineClass . So far so good. That works. BUT: If I in a class (in the jar) want to access another class in the same jar, it will not work as the system default class loader is invoked and the class is of course not found (as the jar is only in memory and not on the HD). I've noticed that DefineClass can be passed a class loader reference (jobject), but how do I make a C++ class loader to be passed as such an object??
TIA
/Rob

Answer 1

Hi,
why exactly are you implementing a classloader in C++ ?
Is this some prototype for securely loading classes which can't be decompiled because it's in native code ?
Here's my theory anyways... could be wrong but worth a shot...
I think you're probably trying to do too much on the C++ side.
At best I think the C++ should load the class definition and return an array of bytes representing the class file.
You call this within your Java implementation of FindClass(), and call defineClass() on the Java side.... eg.
public MyCPPClassLoader extends ClassLoader
      static
              // load your native C++ library ( .dll or .so )
              System.loadLibrary ( "cppLoader" );
     private native byte[] cppLoadClass ( String name );
     protected  Class findClass(String name) 
          // call native library to load the class from an arbitrary source
          byte[] classDef = cppLoadClass ( name );
          // let the normal class loader functionality do the work for us
          return ( defineClass ( name, classDef, 0, classDef.length ) );
}regards,
Owen