public Class<?> getFunctionClass() {
    if (isGenericUDF()) {
      if (genericUDF instanceof GenericUDFBridge) {
        return ((GenericUDFBridge) genericUDF).getUdfClass();
      } else {
        return genericUDF.getClass();
      }
    } else if (isGenericUDAF()) {
      if (genericUDAFResolver instanceof GenericUDAFBridge) {
        return ((GenericUDAFBridge) genericUDAFResolver).getUDAFClass();
      } else {
        return genericUDAFResolver.getClass();
      }
    } else if (isGenericUDTF()) {
      return genericUDTF.getClass();
    }
    if(isTableFunction()) {
      return this.tableFunctionResolver;
    }
    return null;
  }
Get the Class of the UDF.
ql/src/java/org/apache/hadoop/hive/ql/exec/FunctionInfo.java