code: public static Object getFieldValue(Field field, Object obj) {
          if (field == null) {
              throw new IllegalArgumentException("field cannot be null.");
          }
          try {
              return field.get(obj);
          } catch (IllegalArgumentException e) {
              throw new Siren4JRuntimeException(e);
          } catch (IllegalAccessException e) {
              throw new Siren4JRuntimeException(e);
          }
      }
docs: Convenience method to retrieve the field value for the specified object wrapped to
  catch exceptions and re throw as <code>Siren4JRuntimeException</code>.
  
  @param field cannot be <code>null</code>.
  @param obj may be <code>null</code>.
  @return the value, may be <code>null</code>.