Question

I’m trying to create a dynamic survey application in Prime Faces. I have a list of Question Objects that each contains a list of AnswerChoices. These are given to the f:selectItems value attribute. This is fine. The question object also contains a List of selectedValues which is given to the relevant selectOne/many component.

Because I’m looking to be generic, there will be questions that have multiple selected values and also some that have only one selected value. I wanted to be able to point the selectOne and selectMany components to the List of strings within the relevant Question object that represents the selectedValues.

This works ok for the selectMany component, but not for the selectOne component which needs to be pointed at a singular object rather than a list. Is there an easy way around this that I’m missing – as I’d like to only have one object representing the selectedValues if possible

Answer 1

You can use brace notation to bind the value to a list/array item at a specific index. The below example binds the value to the 1st item of the list/array.

<h:selectOneMenu value="#{bean.selectedAnswers[0]}" />

There’s however a caveat: you need to prepare the list/array with the single item yourself during bean’s (post)construction. JSF/EL won’t do that in case of a <h:selectOneMenu>.

E.g.

@PostConstruct
public void init() {
    selectedAnswers = new ArrayList<Answer>();
    selectedAnswers.add(null);
}

It doesn’t harm to reuse this preinitializated property for UISelectMany components by the way.