Q:

 XML shown as plain text after ajax redirect on security constraint in WildFly

I've got this weird problem with ajax redirect on a security constraint:
When an ajax call is made (by clicking on a sortable p:dataTable column or when a p:poll triggers) on a role-secured page after my session timed out, a <partial-response><redirect-url=... XML from OmniFaces is shown on the screen.
When I remove OmniFaces, the ajax calls seem to fail silently and I don't get the XML shown.
Security is configured as following in web.xml:
<security-constraint>
    <web-resource-collection>
        <web-resource-name>Pages</web-resource-name>
        <url-pattern>/*</url-pattern>
    </web-resource-collection>
    <auth-constraint>
        <role-name>user</role-name>
    </auth-constraint>
</security-constraint>

<security-constraint>
    <web-resource-collection>
        <web-resource-name>Resources</web-resource-name>
        <url-pattern>/javax.faces.resource/*</url-pattern>
    </web-resource-collection>
</security-constraint>

<login-config>
    <auth-method>FORM</auth-method>
    <realm-name>myRealm</realm-name>
    <form-login-config>
        <form-login-page>/login.xhtml</form-login-page>
        <form-error-page>/login.xhtml?error=true</form-error-page>
    </form-login-config>
</login-config>

<security-role>
    <role-name>user</role-name>
</security-role>

A:

I reproduced it. This is a strange quirk/bug in WildFly itself.
What's happening here?
By default, without OmniFaces, when a request is fired on a constrained page while the session is expired, the server by default returns the entire HTML page identified by <form-login-page> as response, regardless of the source of the request. This obviously fails with JSF ajax requests as the JavaScript responsible for processing ajax requests couldn't deal with a whole HTML page as response where it expected a special XML response. The user is left with no form of feedback. This is since OmniFaces 1.2 fixed in its OmniPartialViewContext, triggered by this related question: ViewExpiredException not thrown on ajax request if JSF page is protected by j_security_check.
With OmniFaces, a special JSF ajax redirect response in form of <partial-response><redirect url="originalURL"> is returned instead of the entire login page, and the security constraint is triggered once again, but this time with a real synchronous request instead of an JSF ajax request. When the server returns the entire <form-login-page>, it would work just fine this way.
WildFly (tested only 10.0.0 as of now), however, appears to cache the entire <form-login-page> response of the 1st security constraint hit in the session (whereas it is expected to cache only the associated request) and return exactly that response on every hit of a constrained request. That's why you see the initial <partial-response> XML response every time.
As per this commit I have bypassed it by explicitly invalidating the session once again before generating the ajax redirect in OmniPartialViewContext. The fix is available in OmniFaces 2.3.

