Java HotSpot Virtual Machine

I encountered great difficulties in JNI.

I have a java class,
public class GeneralName
{
public int nametype = 0;
public Object namevalue = null;

public GeneralName() {}
public GeneralName(GeneralName gname)
{
setGeneralName(gname.nametype, gname.namevalue);
}
public void setGeneralName(int nType, Object valueobj)
{
nametype = nType;
if ( nType == 0 )
{
String strname = (String)valueobj
namevalue = new String(strname);
}
if ( nType == 1 )
{
LV lvname = (LV)valueobj;
namevalue = new LV(lvname);
}
}
}
and I have a c/c++ structure,
typedef struct GeneralName {
int ntype;
void *pnamevalue;
} GeneralName;

In JNI, I don't know how to convert void pointer to java Object?
Is there anyone can help me?
thanks in advance, and best regards.