public String build() {
      StringBuilder result = new StringBuilder();

      if (maxBodyBytesLength == null) {
        maxBodyBytesLength = MAX_BODY_BYTES_LENGTH;
      }
      if (maxBodyCharsLength == null) {
        maxBodyCharsLength = MAX_BODY_CHARS_LENGTH;
      }
      if (response.reason() != null) {
        result.append(format("[%d %s]", response.status(), response.reason()));
      } else {
        result.append(format("[%d]", response.status()));
      }
      result.append(
          format(
              " during [%s] to [%s] [%s]",
              response.request().httpMethod(), response.request().url(), methodKey));

      result.append(format(": [%s]", getBodyAsString(body, response.headers())));

      return result.toString();
    }
The Response body.

@return an Optional wrapping the response body.
core/src/main/java/feign/FeignException.java