Save state of ViewScoped bean

Question

I'm building a JSF application using Mojarra 2.1.6 implementation. My application screens are @ViewScoped and each bean is being destroyed from one view to another one. Also I want to have a kind of navigation bar or breadcrumb, so the user can go back from page to page using it. To achieve that I'm using Primefaces p:button , in this way:

<h:panelGroup
      rendered="#{!navigationManager._DisableNavigationButtons}">
<p:toolbar>
    <p:toolbarGroup>
        <ui:repeat value="#{navigationManagerSystem._Navegables}"
                                        var="item">
            <p:button value="#{item._Title}" outcome="#{item._IncludePath}">
                <f:param name="params" value="#{item._NavigationParams}" />
            </p:button>
        </ui:repeat>
        <p:button disabled="true"
            value="#{navigationManagerSystem._Navegable._Title}" />
    </p:toolbarGroup>
</p:toolbar>

As you can see in this code, it's basically a toolbar with buttons, this buttons are saving old url's, so when user clicks one of them he can go back.

However, my problem is that I have some pages which are receiving view parameters and I want to do something generic, so the best idea would be to save parameters in a java.util.List ( navigationManagerSystem is a @SessionScoped bean) in order to recover them when user clicks a button to go back, to achieve the old bean state.

But the example above is not working, even the destination page is written in that way

<ui:composition xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:c="http://java.sun.com/jsp/jstl/core"
xmlns:p="http://primefaces.org/ui"
template="/templates/general_template.xhtml">

<ui:define name="metadata">
    <f:metadata>
        <f:viewParam id="user" name="user"
            value="#{navegableUserData._ParamUser}" required="true"
            requiredMessage="User is required" />
        <f:viewParam id="params" name="params"
            value="#{navegableUserData._NavigationParams}" />
        <f:event type="preRenderView"
            listener="#{navegableUserData.initialize}" />
    </f:metadata>
    <h:message for="user" />
</ui:define>

<ui:define name="general_content">
    <p:outputPanel autoUpdate="false" id="Datos_Loged" name="Datos_Loged"
        layout="block">
        <h:form id="SystemUserForm">
            <ui:include
                src="/system/manage_user/content/edit_user/system_user_data/system_user.xhtml" />
        </h:form>
    </p:outputPanel>
</ui:define>

_NavigationParams setter is not being invoked and I have a conversion exception. I don't know if there is a better way to do this in JSF, maybe maintaining the @ViewScoped beans...

Answer 1

The f:viewParam, f:param manages the setting, conversion and validation of GET parameters. Therefore the url will be something like newPage.jsf?param=10. If you try to put aa list of classes in the get parametter there will be an error because the get parameter must be a string.

Answer 2

I think the solution can be not to pass the parameters directly through the view. Just host them into navigationManager bean which is @SessionScoped and controls the queue of buttons. Anyway, I need to know which button is clicked in order to recover the params from my @ViewScoped bean, an index value through the view would be enough, wouldn't it?

That way I can also remove buttons that are after the one clicked in order to maintain the breadcrumb updated.

Anyway, other ideas are welcome.