PrettyFaces error with required attribute

I'm developing a web application using JSF 2 and prettyfaces. I annotated one of my @ViewScoped beans with pretty annotations. That's what I have:

@ManagedBean
@ViewScoped
@URLMapping(parentId = "app-list", id = "app-view", pattern = "/detail/#{appId}",
    viewId = "/system/manage_app/content/app_detail/app_detail.xhtml")
public class NavegableAppView extends SystemNavegable {

/**

Basically that shows the details of an application which is installed in my system. This bean can be instanced in two ways, passing #{appId} param, which indicates the id of the application which I want to load, or without that param, in this case the bean will recover this id from a @SessionScoped bean.

That's how the page /system/manage_app/content/app_detail/app_detail.xhtml is managing the parameter:

<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="appId" name="appId"
            value="#{navegableAppView._ParamApp}" required="false" />
        <f:event type="preRenderView"
            listener="#{navegableAppView.initialize}" />
    </f:metadata>
</ui:define>

<ui:define name="general_content">
    <p:panel>
<!--More stuff-->

The problem here is I want NavegableAppView bean to be created, with or without param. I have tried this way <p:button value="prueba" outcome="pretty:app-view" /> which works but limits me to do nothing more than outcome and also <p:commandButton value="prueba2" action="pretty:app-view" ajax="false" />, which is the equivalent to call an action method and return the navigation case (that's what really I want).

First choice creates the bean properly and loads the value from the session. Second case, is giving me this error:

 HTTP 500 - PrettyFaces: Exception occurred while building URL 
 for MappingId < app-view >, Required value < #{appId} > was null

So my target bean is not getting constructed. I have tried adding the parameter manually to the navigation case: return pretty:app-view?appId=1 and it works, but I want the target bean to recover it from the session itself. Do I have to call a redirect or something like that in my action method?

Pool your ideas.

So you are actually running into one of the "edge" effects of PrettyFaces. The "appId" parameter you have defined is actually treated both a parameter name, and also an EL bean value location for building links.

@URLMapping(parentId = "app-list", id = "app-view", pattern = "/detail/#{appId}",
viewId = "/system/manage_app/content/app_detail/app_detail.xhtml")

When you use the postback-action navigation functionality of PrettyFaces, it requires an EL bean name. Now, it just so happens that since you have not provided one in your @URLMapping annotation, that PrettyFaces is going to try to use the parameter name anyway, and hope that it can find what you want. In this case, obviously, there is no bean value called #{appId}.

You're really mixing two types of functionality that attempt to solve the same problem. Your <f:metadata> and <f:viewParam> definitions are doing the same thing that PrettyFaces does with its path-parameters and action methods. You should use one or the other mechanism. If you really want to mix them, then as you said, you should be invoking actual navigation from your <h:commandButton>, like so:

<p:commandButton value="prueba2" action="#{navegableAppView.goToAppId}" ajax="false" />

Then, you'll need to make sure you return a valid JSF2 navigation string WITH the appId parameter, such as:

public String goToAppId() {
    return "/system/manage_app/content/app_detail/app_detail.xhtml?faces-redirect=true&appId=" + appId";
}

PrettyFaces will then understand that you are redirecting to a URL that has been mapped, and will perform outbound rewriting on the URL, and send you to the proper, /detail/#{addId} instead. This is all in the docs.

The final option would simply to remove the <f:metadata> and <f:viewParam>, and use the built-in PrettyFaces functionality for managing view parameters instead. Simply removing the metadata and updating your @URLMapping to this, would solve your problem:

@ManagedBean
@ViewScoped
@URLMapping(parentId = "app-list", id = "app-view", pattern = "/detail/#{appId : navegableAppView._ParamApp}",
viewId = "/system/manage_app/content/app_detail/app_detail.xhtml")
public class NavegableAppView extends SystemNavegable {

@URLAction
public String initialize() {
if ( appId != null ) {
      this.item = appsDB.findById(appId);
      return null;
    }

    // Add a message here, "The item {..} could not be found."
    return "pretty:app-list";
}

This is how you initialize pages using PrettyFaces. When it comes down to it, if you are using pretty:mappingId navigation, you should only use PrettyFaces features. If you are going to use normal JSF2-style navigation where you specify the view-id and all the parameters of the URL, then you can mix-and match (as long as you are using named path-parameters in your URL mappings.

I hope this helps.