Vaadin 7.4 , Spring, Tomcat 7 , Change context root using @WebServlet

I'm using Vaadin 7.4 with Spring using the "spring4vaadin" - Project. I'm deploying the Application on a Tomcat 7.0.29 with Servlet API 3.0.

I deploy the Application under the Root-Context of Tomcat ("/") and I'm using the @WebServlet-Annotation to set the actual context of the App to "/esb/*":

@WebServlet( value = "/esb/*"  , asyncSupported = true )
public static class Servlet extends SpringVaadinServlet {

}

But every time when I navigate to the App-URL "http://localhost:8080/esb/" I get the error message: "Failed to load the bootstrap javascript ./../VAADIN/vaadinBootstrap.js?v=7.4.0" in a Browser-Pop-Up from Vaadin.

By web.xml looks like this:

<web-app id="ESAB_Cutting_Prototyping" version="3.0"
     xmlns="http://ift.tt/nSRXKP"
     xmlns:xsi="http://ift.tt/ra1lAU"
     xsi:schemaLocation="http://ift.tt/nSRXKP
     http://ift.tt/1u51vgk"
     metadata-complete="false">
</web-app>

If I set the context in the Tomcat Deployment-Configuration of my Intellij IDE it works without any problems.

I have no idea what to do - any help is greatly appreciated.