Java Tips - How to write a servlet filter which doesn't allow caching

This J2EE tip explains a method of implementing a servlet filter that do not allow caching. This may forbid the browser and any intervening cache from caching the results of the request.


import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.ServletResponse;

import javax.servlet.ServletRequest;

import javax.servlet.Filter;

import javax.servlet.FilterConfig;

import javax.servlet.FilterChain;

import javax.servlet.http.HttpServletResponse;



public class NoCacheFilter implements Filter {

  private FilterConfig filterConfig = null;

  

  public void init(FilterConfig filterConfig) {

    this.filterConfig = filterConfig;

  }

  

  public void destroy() {

    this.filterConfig = null;

  }



  /*The real work happens in doFilter(). 

  The reference to the response object is of type ServletResponse,

  so we need to cast it to HttpServletResponse:

  */



  public void doFilter(ServletRequest request, ServletResponse response,

      FilterChain chain)

      throws IOException, ServletException {

    HttpServletResponse httpResponse = (HttpServletResponse) response;



    /*Then we just set the appropriate headers

    and invoke the next filter in the chain:

    */

    httpResponse.setHeader("Cache-Control", "no-cache");

    httpResponse.setDateHeader("Expires", 0);

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

    chain.doFilter(request, response);

    /* this method calls other filters in the order they are 

    written in web.xml

    */

  }

}

Related Tips