cython 0.19 fixes, jlong was interpreted as a number, not as a pointer value anymore.
add a better repr for LocalRef class (ie, indicate the source reference we came from.)
Add __javacontext__ for proxy class, which can be either "system" or "app". Default goes to system if non existent.
Also check the exception before trying to convert the returned value, as i've experienced, sometimes the value returned is not NULL, but is not valid at all, cause an exception happen.