@Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {

        HttpServletResponse httpResponse = (HttpServletResponse) response;
        httpResponse.addHeader("Cache-Control", "no-cache");
        httpResponse.addHeader("Pragma", "no-cache");
        
        chain.doFilter(request, response);
        
    }
Filter that sets the HTTP response headers necessary to request that the
browser always revalidate its cached copy of the response before using that
cached copy.
guacamole/src/main/java/org/apache/guacamole/CacheRevalidationFilter.java