After log out of my user, on back button of browser previous logged in user data is leaking in java

Question

At signout of user, this method is hit. But on pressing back button user data is getting leaked (not getting logged in again).

@RequestMapping(value = {"signout"})
public String signout(HttpServletRequest req, ModelMap map) {
    this.objSession = req.getSession(false);
    if (this.objSession.getAttribute("userid") != null) {
        this.objSession.removeAttribute("userid");
        this.objSession.removeAttribute("usertype");
        // this.objSession.invalidate();

        Cookie c = new Cookie("JSESSIONID", null);
    }
    return "redirect:/home.htm";
}