generic java response header filter

ResponseHeaderFilter.java

package mo.nkeyco.de;

import java.io.IOException;
import java.util.Enumeration;

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.HttpServletResponse;

/* http://www.symphonious.net/2007/06/19/caching-in-tomcat/ */

public class ResponseHeaderFilter implements Filter {

	private FilterConfig config;

	@Override
	public void init(FilterConfig config) throws ServletException {
		this.config = config;
	}	

	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
			throws IOException, ServletException {
		
		HttpServletResponse httpResp = (HttpServletResponse) response;
		Enumeration e = config.getInitParameterNames();

		while (e.hasMoreElements()) {
			String name = (String) e.nextElement();
			String value = config.getInitParameter(name);
			httpResp.addHeader(name, value);
		}
		
		chain.doFilter(request, response);
	}
	
	@Override
	public void destroy() {
		/* im not sure if there is anything we need to do on destroy -dL */
	}

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0" metadata-complete="true">
	
	<!-- some WEB.XML goodness -->

	<filter>
	<!-- http://www.symphonious.net/2007/06/19/caching-in-tomcat/ -->
		<filter-name>NoCache</filter-name>
		<filter-class>mo.nkeyco.de.ResponseHeaderFilter</filter-class>
		<init-param>
		<!-- this is preferred for the 1.1 spec and is used by CLIENT BROWSERS -->
			<param-name>Cache-Control</param-name>
			<param-value>no-cache, must-revalidate</param-value>
		</init-param>
		<init-param>
		<!-- this is for devices between server and client, like VIP, F5, load-balancers, caches and proxies
				also some 1.0 clients respect this -->
			<param-name>Pragma</param-name>
			<param-value>no-cache</param-value>
		</init-param>
		<init-param>
		<!-- older browsers may not honor the Cache-Control from v1.1, Expires existed in 1.0 spec -->
			<param-name>Expires</param-name>
			<param-value>0</param-value>
		</init-param>
	</filter>

	<filter>
		<filter-name>CacheOneDay</filter-name>
		<filter-class>mo.nkeyco.de.ResponseHeaderFilter</filter-class>
		<init-param>
			<param-name>Cache-Control</param-name>
			<param-value>max-age=86400, public</param-value>
			<!-- a week would be '604800' -->
		</init-param>
		<!-- dont know if 'Pragma' has/needs any age optione -->
		<!-- to use 'Expires' you would need to tweek the Java to calculate the time for you-->
	</filter>


	
	<!-- this will prevent some files from being cached. -->
	<filter-mapping>
		<filter-name>NoCache</filter-name>
		<!-- i also made a CacheOneDay filter you can try, you can tweek it for a CacheOneWeek or whatever you want -->
		<url-pattern>/scripts/lib/no-cache/*</url-pattern>
	</filter-mapping>


	<!-- other WEB.XML goodness -->

</web-app>