Supplying parameters through p:remoteCommand to a

问题:

The following XHTML sets a selected value in <p:selectOneMenu> to a request scoped bean through <p:remoteCommand>.

<h:form id="languageForm" prependId="true">

    <pe:blockUI target=":body" widgetVar="blockBodyUIWidget">
        <h:panelGrid columns="2">
            <h:graphicImage library="default" name="images/ajax-loader1.gif" class="block-ui-image"/>
            <h:outputText value="#{messages['blockui.panel.message']}" class="block-ui-text"/>
        </h:panelGrid>
    </pe:blockUI>

    <p:selectOneMenu id="languages" value="#{localeBean.language}" onchange="changeLanguage([{name:'language', value:this.value}]);">
        <f:selectItem itemValue="en" itemLabel="#{messages['languages.english']}" />
        <f:selectItem itemValue="hi" itemLabel="#{messages['languages.hindi']}" />
    </p:selectOneMenu>

    <p:remoteCommand name="changeLanguage" process="@this" update="@none" onstart="PF('blockBodyUIWidget').block();" oncomplete="PF('blockBodyUIWidget').unblock();" action="#{intermediateLocaleBean.localeAction}"/>
</h:form>

The corresponding JSF managed bean:

@ManagedBean
@RequestScoped
public final class IntermediateLocaleBean
{
    @ManagedProperty("#{param.language}")
    private String language;
    @ManagedProperty("#{localeBean}")
    private LocaleBean localeBean;  //Injecting another session scoped bean here.

    public IntermediateLocaleBean() {}

    public void setLanguage(String language) {
        this.language = language;
    }

    public void setLocaleBean(LocaleBean localeBean) {
        this.localeBean = localeBean;
    }

    public String localeAction()
    {
        localeBean.setLocale(language.equals("hi")?new Locale(language, "IN"):new Locale(language));
        return FacesContext.getCurrentInstance().getViewRoot().getViewId() + "?faces-redirect=true";
    }
}

The language property is initialized to the selected language in <p:selectOneMenu>. This is all done as it is a JSF managed bean.

---

What if, the bean is maintained by Spring like as follows?

@Controller
@Scope("request")
public final class IntermediateLocaleBean
{
    //Do something to initialize the property - language.
    //@ManagedProperty would not work as this bean is managed by Spring.
    //It is not initialized to the selected language in <p:selectOneMenu>.
    //It is null.

    private String language;

    //The session scoped bean is injected using the @Autowired annotation as follows.

    @Autowired
    private final transient LocaleBean localeBean=null;

    public IntermediateLocaleBean() {}

    public void setLanguage(String language) {
        this.language = language;
    }

    public String localeAction()
    {
        localeBean.setLocale(language.equals("hi")?new Locale(language, "IN"):new Locale(language));
        return FacesContext.getCurrentInstance().getViewRoot().getViewId() + "?faces-redirect=true";
    }
}

How to initialize the language property to the selected language in <p:selectOneMenu> in this bean?

回答1:

Traditionally, the parameter value of language - a request parameter, could be made available using

FacesContext context = FacesContext.getCurrentInstance();
String language = context.getExternalContext().getRequestParameterMap().get("language");

like the following,

@Controller
@Scope("request")
public final class IntermediateLocaleBean
{
    @Autowired
    private final transient LocaleBean localeBean=null;

    public IntermediateLocaleBean() {}

    public void setLanguage(String language) {
        this.language = language;
    }

    public String localeAction()
    {
        String language = FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("language");
        localeBean.setLocale(language.equals("hi")?new Locale(language, "IN"):new Locale(language));

        return FacesContext.getCurrentInstance().getViewRoot().getViewId() + "?faces-redirect=true";
    }
}

But I personally dislike exposing the entire request using FacesContext unless it is absolutely necessary.

---

There is an org.springframework.beans.factory.annotation.Value annotation in Spring that can be used with the Spring expression language to obtain request parameters as follows.

@Controller
@Scope("request")
public final class IntermediateLocaleBean
{
    @Value("#{request.getParameter('language')}") //Exposing the value of language.
    private String language;

    @Autowired
    private final transient LocaleBean localeBean=null;

    public IntermediateLocaleBean() {}

    public void setLanguage(String language) {
        this.language = language;
    }

    public String localeAction()
    {
        localeBean.setLocale(language.equals("hi")?new Locale(language, "IN"):new Locale(language));
        return FacesContext.getCurrentInstance().getViewRoot().getViewId() + "?faces-redirect=true";
    }
}

The value of language supplied by <p:remoteCommand> as a request parameter is now available in this bean using the @Value annotation (the getter method for language is not required in my case).

_{Please suggest or add another answer, if something else is available!}