IllegalArgumentException thrown from ParamConverter#fromString is converted into a default value by SingleValueExtractor

[bobtiernay-okta]

From ParamConverter#fromString

IllegalArgumentException - if the supplied string cannot be parsed or is null.

And from SingleValueExtractor#extract:

    /**
     * {@inheritDoc}
     * <p/>
     * This implementation extracts the value of the parameter applying the underlying
     * {@link ParamConverter param converter} to the first value found in the list of potential multiple
     * parameter values. Any other values in the multi-value list will be ignored.
     *
     * @param parameters map of parameters.
     * @return extracted single parameter value.
     */
    @Override
    public T extract(final MultivaluedMap<String, String> parameters) {
        final String value = parameters.getFirst(getName());
        try {
            return fromString((value == null && isDefaultValueRegistered()) ? getDefaultValueString() : value);
        } catch (final WebApplicationException | ProcessingException ex) {
            throw ex;
        } catch (final IllegalArgumentException ex) {
            return defaultValue();
        } catch (final Exception ex) {
            throw new ExtractorException(ex);
        }

I'm trying to understand if this is a bug or expected behavior. I was expecting that this would get mapped to a 400 by default, but instead it silently gets converted to the default value.

Either way, I think both sets of JavaDoc should be enhanced to clarify this case as it seems to violate the principle of least surprise.

[chrisolson443]

And you don't have a @DefaultValue annotation for the param, right? Assuming that's true, I agree that this is confusing. As it is...throwing an IllegalArgumentException has no affect, i.e., the incoming request passes right through to the resource class for normal processing

[bobtiernay-okta]

I can't recall anymore, but the code stands on it's own :)