package org.kuali.student.common.util.filter;

 import java.io.IOException;

 import java.util.Date;

 import javax.servlet.Filter;

 import javax.servlet.FilterChain;

 import javax.servlet.FilterConfig;

 import javax.servlet.ServletException;

 import javax.servlet.ServletRequest;

 import javax.servlet.ServletResponse;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 /**

  * 

  * This class ensures that the nochache.js files are in fact, not cached. It seems that the file was getting 

  * cached and this was causing odd UI errors to appear. 

  *

  */

 public class GWTCacheControlFilter implements Filter {

         public void destroy() {

         }

         public void init(FilterConfig config) throws ServletException {

         }

         public void doFilter(ServletRequest request, ServletResponse response,

                         FilterChain filterChain) throws IOException, ServletException {

                 HttpServletRequest httpRequest = (HttpServletRequest) request;

                 String requestURI = httpRequest.getRequestURI();

                 if (requestURI.contains(".nocache.")) {

                         Date now = new Date();

                         HttpServletResponse httpResponse = (HttpServletResponse) response;

                         httpResponse.setDateHeader("Date", now.getTime());

                         // one day old

                         httpResponse.setDateHeader("Expires", now.getTime() - 86400000L);

                         httpResponse.setHeader("Pragma", "no-cache");

                         httpResponse.setHeader("Cache-control", "no-cache, no-store, must-revalidate");

                 }

                 filterChain.doFilter(request, response);

         }

 }