public static boolean isAllowBackslash() {
        return isAllowBackslash;
    }
Redirects the to the request url from a previously
{@link #saveRequest(javax.servlet.ServletRequest) saved} request, or if there is no saved request, redirects the
end user to the specified {@code fallbackUrl}.  If there is no saved request or fallback url, this method
throws an {@link IllegalStateException}.
<p/>
This method is primarily used to support a common login scenario - if an unauthenticated user accesses a
page that requires authentication, it is expected that request is
{@link #saveRequest(javax.servlet.ServletRequest) saved} first and then redirected to the login page. Then,
after a successful login, this method can be called to redirect them back to their originally requested URL, a
nice usability feature.

@param request     the incoming request
@param response    the outgoing response
@param fallbackUrl the fallback url to redirect to if there is no saved request available.
@throws IllegalStateException if there is no saved request and the {@code fallbackUrl} is {@code null}.
@throws IOException           if there is an error redirecting
@since 1.0
web/src/main/java/org/apache/shiro/web/util/WebUtils.java