How to pass a parameter along with h:commandButton

Question

One of the most common approaches to change locale in JSF+Seam - with <h:selectOneMenu>:

<h:form  action="#{localeSelector.select}" rendered="false">
    <h:selectOneMenu value="#{localeSelector.language}" onchange="submit()">
        <f:selectItem itemLabel="English" itemValue="en" />
        <f:selectItem itemLabel="Francais" itemValue="fr" />
    </h:selectOneMenu>
</h:form>

I want to implement locale changes with buttons. So, the question is - how to pass the parameter (en, fr, etc.) to update the bean with <h:commandButton>? Maybe <h:inputHidden> would help?

Solution

Either pass as method argument (only if your environment supports EL 2.2),

<h:commandButton value="English" action="#{localeSelector.change('en')}" />
<h:commandButton value="Deutsch" action="#{localeSelector.change('de')}" />
<h:commandButton value="Français" action="#{localeSelector.change('fr')}" />

with

public void change(String language) {
    locale = new Locale(language);
    // ...
}

---

Or use <f:setPropertyActionListener>

<h:commandButton value="English" action="#{localeSelector.change}">
    <f:setPropertyActionListener target="#{localeSelector.language}" value="en" />
</h:commandButton>
<h:commandButton value="Deutsch" action="#{localeSelector.change}">
    <f:setPropertyActionListener target="#{localeSelector.language}" value="de" />
</h:commandButton>
<h:commandButton value="Français" action="#{localeSelector.change}">
    <f:setPropertyActionListener target="#{localeSelector.language}" value="fr" />
</h:commandButton>

with

private String language;

public void change() {
    locale = new Locale(language);
    // ...
}

---

Or use <f:param>

<h:commandButton value="English" action="#{localeSelector.change}">
    <f:param name="language" value="en" />
</h:commandButton>
<h:commandButton value="Deutsch" action="#{localeSelector.change}">
    <f:param name="language" value="de" />
</h:commandButton>
<h:commandButton value="Français" action="#{localeSelector.change}">
    <f:param name="language" value="fr" />
</h:commandButton>

with

public void change() {
    locale = new Locale(FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("language"));
    // ...
}

(you can also let JSF automatically set it by a @ManagedProperty("#{param.language}"), but this requires the bean to be request scoped, or a <f:viewParam>, see also ViewParam vs @ManagedProperty(value = "#{param.id}"))

---

Enough ways to pass a parameter from view to controller. Take your pick. The <h:inputHidden> serves in JSF context a somewhat different purpose and it can only be manipulated by JavaScript in the onclick which is ugly.

Comments

[Serga]

Thank you for complete answer! I didn't took advantage of EL 2.2 because there seem to be no method in Seam LocaleSelector class that takes locale as a parameter. I've also tried <f:param>, but it didn't work because the parameter was not bind with localeSelector.language (or maybe I am missing something in these cases?). Anyway <f:setPropertyActionListener> solved my problem

[BalusC]

You're welcome. I didn't expect #{localeSelector} to be a Seam-proprietary bean (I don't do Seam). I just assumed outright standard JSF with full control over own code.

[Serga]

Yes, I got that - I should make it clear in my post. I just wanted to clarify. Thanks again)