Allow Turbolinks to update the browser address bar correctly after an ajax request is redirected

TurboLinksUrlFilter.java

/**
 * Provide the correct response URL to turbolinks in the 'X-XHR-Current-Location' header. Used to update the browser 
 * history after an ajax request is redirected.
 *
 * @author barry
 * @since 2013/01/24 11:46 AM
 */
public class TurboLinksUrlFilter implements Filter {

    /**
     * turbolinks checks for this header by default
     */
    private static final String RESPONSE_HEADER = "X-XHR-Current-Location";
    private static final String REQUEST_HEADER = "X-XHR-Referer";

    public void init(FilterConfig config) throws ServletException {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        HttpServletResponse response = (HttpServletResponse) resp;
        HttpServletRequest request = (HttpServletRequest) req;
        if (!response.isCommitted() && request.getHeader(REQUEST_HEADER) != null) {
            response.setHeader(RESPONSE_HEADER, getFullURL(request));
        }
        chain.doFilter(req, resp);
    }

    public void destroy() {
    }

    private String getFullURL(HttpServletRequest request) {
        StringBuffer url = request.getRequestURL();
        if (request.getQueryString() != null) {
            url.append('?');
            url.append(request.getQueryString());
        }
        return url.toString();
    }
}