java:64: error: cannot find symbol

I'm new to the Mendix platform and developing an App to learn more. I upgraded from 6.10.4 to 7.1.0 and when running I get the error below listed.

Buildfile: C:\Users\Max\Documents\Mendix\DBapp-main_2\deployment\build_core.xml

compile:
    [javac] Compiling 41 source files to C:\Users\Max\Documents\Mendix\DBapp-main_2\deployment\run\bin
    [javac] C:\Users\Max\Documents\Mendix\DBapp-main_2\javasource\appcloudservices\OpenIDHandler.java:350: error: cannot find symbol
    [javac]    resp.addCookie(RequestHandler.XAS_SESSION_ID, "", "/", "", 0, true);
    [javac]                                 ^
    [javac]   symbol:   variable XAS_SESSION_ID
    [javac]   location: class RequestHandler
    [javac] C:\Users\Max\Documents\Mendix\DBapp-main_2\javasource\appcloudservices\SessionInitializer.java:46: error: cannot find symbol
    [javac]   String sessionid = req.getCookie(RequestHandler.XAS_SESSION_ID);
    [javac]                                                  ^
    [javac]   symbol:   variable XAS_SESSION_ID
    [javac]   location: class RequestHandler
    [javac] C:\Users\Max\Documents\Mendix\DBapp-main_2\javasource\appcloudservices\SessionInitializer.java:64: error: cannot find symbol
    [javac]   resp.addCookie(RequestHandler.XAS_SESSION_ID, session.getId().toString(),"/" ,"" ,-1, true );
    [javac]                                ^
    [javac]   symbol:   variable XAS_SESSION_ID
    [javac]   location: class RequestHandler
    [javac] Note: Some input files use or override a deprecated API.
    [javac] Note: Recompile with -Xlint:deprecation for details.
    [javac] 3 errors