code: protected Deserializer getDefaultDeserializer(Class cl) {
          if (InputStream.class.equals(cl))
              return InputStreamDeserializer.DESER;
  
          if (_isEnableUnsafeSerializer) {
              return new UnsafeDeserializer(cl);
          } else
              return new JavaDeserializer(cl);
      }
docs: Returns the default serializer for a class that isn't matched
  directly.  Application can override this method to produce
  bean-style serialization instead of field serialization.
  
  @param cl the class of the object that needs to be serialized.
  @return a serializer object for the serialization.