JSF 1.2空 <h:selectManyListbox /> 验证问题

Question

I'm kind of new to JSF and I'm having trouble to understand what values JSF renders in a form after its validation fails. Im using WebSphere 7 and its default implementation of JSF, MyFaces (I think 2.0).

My xhtml looks like this:

<h:form id="form">
    <h:inputText id="text" value="#{backing.text}" required="true"/>
    <h:message for="text" />

    <h:selectManyListbox id="options" value="#{backing.options}" required="true">
        <f:selectItem itemLabel="1" itemValue="1" />
        <f:selectItem itemLabel="2" itemValue="2" />
        <f:selectItem itemLabel="3" itemValue="3" />
    </h:selectManyListbox>
    <h:message for="options" />

    <h:commandButton value="Save" />
</h:form>

And my backing bean like this:

public class Backing {

    private String text;

    private String[] options;

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

    public String[] getOptions() {
        return options;
    }

    public void setOptions(String[] options) {
        this.options = options;
    }
}

1. I fill the <h:inputText /> with some text.
2. I select two options from the <h:selectManyListbox />
3. I press the 'Save' button
4. The form is rendered with the value I entered for <h:inputText /> and with the options I selected on the <h:selectManyListbox /> (no validation messages are shown, as expected)
5. Now ...
6. I empty the <h:inputText />
7. I deselect the two options from the <h:selectManyListbox />
8. I press the 'Save' button
9. The form renders the <h:inputText /> empty and the <h:selectManyListbox /> with the previous options I had selected (both validation messages are shown, as expected)

As you can see, the behaviour when rendering the <h:inputText /> and the <h:selectManyListbox /> is different:

• <h:inputText /> renders component's submitted value
• <h:selectManyListbox /> renders bean's value

I've been trying to render <h:selectManyListbox /> with no options selected without hacking or messing my code, but had no luck.

¿Is this some bug? ¿Am I missing something?

Answer 1

The less hacky solution I found is to copy and re-implement the method renderOption , overriding the default MenuRenderer .

The original source is something like this as I had to decompile (version 1.2_13). Notice that I'm pasting only the lines that actually need to be changed. If you need to use this solution you will have to copy the full contents of the method :

public class MenuRenderer extends HtmlBasicInputRenderer {
    protected void renderOption(FacesContext context, UIComponent component, Converter converter, SelectItem curItem, Object currentSelections, Object[] submittedValues, HtmlBasicRenderer.OptionComponentInfo optionInfo) throws IOException {
        (...)
        Object valuesArray;
        Object itemValue;
        if (submittedValues != null) {
            boolean containsValue = containsaValue(submittedValues);
            if (containsValue) {
                valuesArray = submittedValues;
                itemValue = valueString;
            } else {
                valuesArray = currentSelections;
                itemValue = curItem.getValue();
            }
        } else {
            valuesArray = currentSelections;
            itemValue = curItem.getValue();
        }
        (...)
    }
}

I created CustomListboxRenderer ( ListboxRenderer extends MenuRenderer ) like this:

public class CustomListboxRenderer extends ListboxRenderer {
    @Override
    protected void renderOption(FacesContext context, UIComponent component, Converter converter, SelectItem curItem, Object currentSelections, Object[] submittedValues, HtmlBasicRenderer.OptionComponentInfo optionInfo) throws IOException {
        (...)
        Object valuesArray;
        Object itemValue;
        if (submittedValues != null) {
            valuesArray = submittedValues;
            itemValue = valueString;
        } else {
            valuesArray = currentSelections;
            itemValue = curItem.getValue();
        }
        (...)
    }
}

and then added in faces-config the next lines:

<render-kit>
    <renderer>
        <component-family>javax.faces.SelectMany</component-family>
        <renderer-type>javax.faces.Listbox</renderer-type>
        <renderer-class>CustomListboxRenderer</renderer-class>
    </renderer>
</render-kit>