CDI Addon + WebSphere + web.xml

I am trying to deploy an CDI App to a WebSphere Server! When I deploy the war without the deployment descriptor, everything works fine.

But when I try to deploy the Application with a web.xml deployment descriptor, no Injection will work ...
Unfortunately I have to use a dep. desc., because I need to add a Servlet filter to my Application...

My deployment descriptor looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<web-app
        id="LohnzettelOnline" version="2.4"
        xmlns="http://java.sun.com/xml/ns/j2ee"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
     http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

    <servlet>
        <servlet-name>LohnzettelOnline</servlet-name>
        <servlet-class>at.sozvers.pva.lohnzettelonline.ui.Servlet</servlet-class>

        <init-param>
            <description>Vaadin UI provider to use.</description>
            <param-name>UIProvider</param-name>
            <param-value>com.vaadin.cdi.CDIUIProvider</param-value>
        </init-param>
    </servlet>

    <servlet-mapping>
        <servlet-name>LohnzettelOnline</servlet-name>
        <url-pattern>/lohnzettelonline/*</url-pattern>
    </servlet-mapping>

    <servlet-mapping>
        <servlet-name>LohnzettelOnline</servlet-name>
        <url-pattern>/VAADIN/*</url-pattern>
    </servlet-mapping>

    <filter>
        <filter-name>LoginFilter</filter-name>
        <filter-class>ui.util.LoginFilter</filter-class>
        <init-param>
            <param-name>dropurl.0</param-name>
            <param-value>/VAADIN/</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>LoginFilter</filter-name>
        <url-pattern>/lohnzettelonline/*</url-pattern>
    </filter-mapping>
</web-app>

Where I have to mention, that my Servlet class is extending the VaadinCDIServlet and has some ServletConfiguration:

@VaadinServletConfiguration(ui = MainUI.class, closeIdleSessions = false, productionMode = false)
public class Servlet extends VaadinCDIServlet {

    @Override
    protected VaadinServletService createServletService(DeploymentConfiguration deploymentConfiguration) throws ServiceException {
        LogManager.getLogger().debug("Vaadin Servlet initialized.");
        return super.createServletService(deploymentConfiguration);
    }

The CDI add-on uses its own servlet. You should remove your servlet from the code and the web.xml.

From https://vaadin.com/wiki/-/wiki/Main/Vaadin+CDI

Remove any existing VaadinServlet from your project (look for servlets with @WebServlet or defined in web.xml). Vaadin CDI has its own VaadinCDIServlet that will be deployed automatically as long as no other Vaadin servlets are present.

As I said, my own Servlet extends the VaadinCDIServlet... So I thought it should work properly, but it didn't.
After a weekend of googling, I realized I am using Servlet API 3.1.0 and can implement the Filter simply with annotating it with @WebFilter!

Thank you for your reply anyway!