Heroku - filter to redirect http requests to https

HttpsFilter.java

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class HttpsFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest httpReq = (HttpServletRequest) request;
        HttpServletResponse httpResp = (HttpServletResponse) response;
        if ("http".equalsIgnoreCase(httpReq.getHeader("x-forwarded-proto"))) {
            StringBuffer requestURL = httpReq.getRequestURL();
            httpResp.sendRedirect("https" + requestURL.substring(requestURL.indexOf(":")));
        } else {
            chain.doFilter(request, response);
        }
    }

    @Override
    public void destroy() {
    }
}