b:selectOneMenu null itemValue

[chongma]

consider the following h:selectOneMenu code snippet:

<h:selectOneMenu value="#{myBean.value}">
	<f:selectItem itemValue="#{null}" itemLabel="Not selected" />
	<f:selectItem itemValue="choice1" itemLabel="choice1" />
	<f:selectItem itemValue="choice2" itemLabel="choice2" />
</h:selectOneMenu>

when Not selected is selected then myBean.value equals null

<b:selectOneMenu label="Nice formatting" value="#{myBean.value}">
	<f:selectItem itemValue="#{null}" itemLabel="Not selected" />
	<f:selectItem itemValue="choice1" itemLabel="choice1" />
	<f:selectItem itemValue="choice2" itemLabel="choice2" />
</b:selectOneMenu>

whereas with b:selectOneMenu when Not selected is selected then myBean.value equals Not selected

[dguna]

I am not sure this is the correct way to do. Selectonemenu does not support null value. If it is empty then the bean has to convert as null.

[stephanrauh]

It was a deliberate choice to use the label if the value is missing, but probably it wasn't a wise choice. I've removed it because we've never documented the feature. Still, it's a breaking change.

Passing null values to the bean is difficult. During my test the null value has always been replaced by an empty string. To avoid that, you probably have to set the parameter javax.faces.INTERPRET_EMPTY_STRING_SUBMITTED_VALUES_AS_NULL to true.

@chongma Can you review and test my changes, please?

[dguna]

Null is not an value. It means empty. JSF treats everything as string and the converters to the rest of the work to convert it to objects. There is no "null" object. This will fail always.

[chongma]

I have been passing nulls for a long time with (usually) no problem. But looking at this answer by @BalusC it seems that @dguna is correct and that the preferred method is to pass an empty string. Not sure why null always worked for me before https://stackoverflow.com/questions/17052503/using-a-please-select-fselectitem-with-null-empty-value-inside-a-pselectonem?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa

[stephanrauh]

@dguna You are right... mostly. Have a look at Bauke's well-researched article.

[stephanrauh]

I'll close this ticket. If anyone of your finds a bug in my bugfix, don't hesitate to re-open the ticket.

[dguna]

Don"t close it yet. You have to give an option as f:selectitems noSelectionOption="true", it means empty string and if required=true, it should not be submitted. JSF automatically converts empty as null, if I am correct. Please look at the Primefaces selectonemenu.

[stephanrauh]

There are several references to noSelectionOption in our source code, so I assume we've already implemented it. For example, have a look at this one:

private SelectItemAndComponent determineSelectedItem(FacesContext context, SelectOneMenu menu, List<SelectItemAndComponent> items, Converter converter) {
		Object submittedValue = menu.getSubmittedValue();
		Object selectedOption;
		if (submittedValue != null) {
			selectedOption = submittedValue;
		} else {
			selectedOption = menu.getValue();
		}

		for (int index = 0; index < items.size(); index++) {
			SelectItemAndComponent option = items.get(index);

                        
			if (option.getSelectItem().isNoSelectionOption()) continue;


			
			Object itemValue = option.getSelectItem().getValue();
			String itemValueAsString = getOptionAsString(context, menu, itemValue, converter);

			Object optionValue;
			if (submittedValue != null) {
				optionValue = itemValueAsString;
			} else {
				optionValue = itemValue;
			}

			if (itemValue != null) {
				if (isSelected(context, menu, selectedOption, optionValue, converter)) {
					return option;
				}
			} 
		}
		return null;
	}