Using a “Please select” f:selectItem with null/empty value inside a p:selectOneMenu

Question

I\'m populating a from database as follows.

Answer 1

In addition to incompleteness, this answer was deprecated, since I was using Spring at the time of this post :

I have modified the converter's getAsString() method to return an empty string instead of returning null, when no Country object is found like (in addition to some other changes),

@Controller
@Scope("request")
public final class CountryConverter implements Converter {

    @Autowired
    private final transient Service service = null;

    @Override
    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        try {
            long parsedValue = Long.parseLong(value);

            if (parsedValue <= 0) {
                throw new ConverterException(new FacesMessage(FacesMessage.SEVERITY_ERROR, "", "The id cannot be zero or negative."));
            }

            Country country = service.findCountryById(parsedValue);

            if (country == null) {
                throw new ConverterException(new FacesMessage(FacesMessage.SEVERITY_WARN, "", "The supplied id doesn't exist."));
            }

            return country;
        } catch (NumberFormatException e) {
            throw new ConverterException(new FacesMessage(FacesMessage.SEVERITY_ERROR, "", "Conversion error : Incorrect id."), e);
        }
    }

    @Override
    public String getAsString(FacesContext context, UIComponent component, Object value) {
        return value instanceof Country ? ((Country) value).getCountryId().toString() : ""; //<--- Returns an empty string, when no Country is found.
    }
}

And 's itemValue to accept a null value as follows.

This generates the following HTML.

    Select
    Country1
    Country2

Earlier, the generated HTML looked like,

    Select
    Country1
    Country2

Notice the first with no value attribute.

This works as expected bypassing the converter when the first option is selected (even though require is set to false). When itemValue is changed to other than null, then it behaves unpredictably (I don't understand this).

No other items in the list can be selected, if it is set to a non-null value and the item received in the converter is always an empty string (even though another option is selected).

Additionally, when this empty string is parsed to Long in the converter, the ConverterException which is caused after the NumberFormatException is thrown doesn't report the error in the UIViewRoot (at least this should happen). The full exception stacktrace can be seen on the server console instead.

If someone could expose some light on this, I would accept the answer, if it is given.