src/main/java/js/servlet/AppServlet.java
private static boolean isEmptyUriRequest(HttpServletRequest httpRequest) {
		if (!"GET".equals(httpRequest.getMethod())) {
			return false;
		}
		String acceptValue = httpRequest.getHeader(HttpHeader.ACCEPT);
		if (acceptValue != null && acceptValue.contains(ContentType.TEXT_HTML.getMIME())) {
			return false;
		}

		String referer = httpRequest.getHeader(HttpHeader.REFERER);
		if (referer == null) {
			return false;
		}

		StringBuilder uri = new StringBuilder(httpRequest.getRequestURI());
		String query = httpRequest.getQueryString();
		if (query != null) {
			if (query.charAt(0) != '?') {
				uri.append('?');
			}
			uri.append(query);
		}
		return referer.toLowerCase().endsWith(uri.toString().toLowerCase());
	}
private static boolean isEmptyUriRequest(HttpServletRequest httpRequest) {
		if (!"GET".equals(httpRequest.getMethod())) {
			return false;
		}
		String acceptValue = httpRequest.getHeader(HttpHeader.ACCEPT);
		if (acceptValue != null && acceptValue.contains(ContentType.TEXT_HTML.getMIME())) {
			return false;
		}

		String referer = httpRequest.getHeader(HttpHeader.REFERER);
		if (referer == null) {
			return false;
		}

		StringBuilder uri = new StringBuilder(httpRequest.getRequestURI());
		String query = httpRequest.getQueryString();
		if (query != null) {
			if (query.charAt(0) != '?') {
				uri.append('?');
			}
			uri.append(query);
		}
		return referer.toLowerCase().endsWith(uri.toString().toLowerCase());
	}
Detect self-referenced request URI. It seems there are browsers considering empty string as valid URL pointing to current
loaded page. If we have an <code>img</code> element with empty <code>src</code> attribute browser will try to load that
image from current URL, that is, the content of current page. This means is possible to invoke a controller many times
for a single page request.
<p>
To avoid such condition check if this request comes from the same page, i.e. referrer is current request. Note that this
is also true for <code>link</code> and <code>script</code> with empty <code>href</code>. Finally worthy to mention is
that this check is not performed on request accepting <code>text/html</code>.

@param httpRequest HTTP request.
@return true only this request is a <code>GET</code> and referrer is request itself.