Enable Cache Filter

This is a simple filter which sets the HTTP headers so that cacheing is enabled. I use this on all the static pages served by my system.

package uk.org.codex.filter;

import java.io.*;
import java.util.*;
import javax.servlet.http.*;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/*******************************************************************************
 * Simple filter which adds headers to the response so that the response is 
 * cached for upto 1 hour.
 * @author  iann
 * @version
 ******************************************************************************/
public class EnableCacheFilter implements Filter {
    
    
    /***************************************************************************
     * Adds appropriate headers to the response to enable cacheing on the client
     * @param req 
     * @param res 
     * @param chain 
     * @throws java.io.IOException 
     * @throws javax.servlet.ServletException 
     **************************************************************************/
    public void doFilter(ServletRequest req, ServletResponse res,FilterChain chain) throws IOException,ServletException {
        
        HttpServletResponse response = (HttpServletResponse) res;
        response.addHeader("Cache-Control", "max-age=3600,public");
        response.addDateHeader("Expires",System.currentTimeMillis() + 1000 * 60 * 60);
        chain.doFilter(req, response);
    }
    
    /***************************************************************************
     * 
     * @param filterConfig 
     **************************************************************************/
    public void init(FilterConfig filterConfig) {
    }
    
    /***************************************************************************
     *
     **************************************************************************/
    public void destroy() {
    }
}

The relavent sections of the web xml file are below. This will enable caching of png, jpg, gif and css files.

<filter>
    <filter-name>EnableCacheFilter</filter-name>
    <filter-class>uk.org.codex.filter.EnableCacheFilter</filter-class>
</filter>
<filter-mapping>
   <filter-name>EnableCacheFilter</filter-name>
   <url-pattern>*.css</url-pattern>
</filter-mapping>
<filter-mapping>
    <filter-name>EnableCacheFilter</filter-name>
    <url-pattern>*.png</url-pattern>
</filter-mapping>
<filter-mapping>
    <filter-name>EnableCacheFilter</filter-name>
    <url-pattern>*.gif</url-pattern>
</filter-mapping>
<filter-mapping>
    <filter-name>EnableCacheFilter</filter-name>
    <url-pattern>*.jpg</url-pattern>
</filter-mapping>

Last updated: 12 Mar 2008 20:15:56

Codex.org.uk

Enable Cache Filter