How to set Expires HTTP header on a single JS file in Apache Tomcat?

Question

I have a js file which is cached between 5-10 minutes, depending on whether I\'m using tomcat from the eclipse (via GWT plugin) or starting tomcat as standalone

Answer 1

Using a javax.servlet.Filter

One way to do this in a portable way (across different app servers), is using Filters. In your web.xml add the following:

  <filter>
    <filter-name>headersFilter</filter-name>
    <filter-class>MyHeadersFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>headersFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

Then implement your MyHeadersFilter like:

public class MyHeadersFilter implements Filter {

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

      final HttpServletRequest httpRequest = (HttpServletRequest) request;
      final String requestUri = httpRequest.getRequestURI();

      final HttpServletResponse httpResponse = (HttpServletResponse) response;


      if (requestUri.contains(".nocache.")) {
        httpResponse.addHeader("Cache-Control", "no-cache");
        ...

      } else if (...) {
        ...
      }

      chain.doFilter(request, response);
  }
}

---

Optional: Configurable Filters

You can also make your filter configurable from your web.xml, by using <init-param>s:

  <filter>
    <filter-name>headersFilter</filter-name>
    <filter-class>MyHeadersFilter</filter-class>
    <init-param>
        <param-name>myParam</param-name>
        <param-value>myValue</param-value>
    </init-param>
  </filter>

Add the following to MyHeadersFilter:

    private FilterConfig filterConfig;

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

    @Override
    public void destroy() {
        this.filterConfig = null;
    }

That makes it possible to access your init-param(s) using:

filterConfig.getInitParameter("myParam")

Answer 2

There is a Filter available in tomcat 7

<filter>
<filter-name>ExpiresFilter</filter-name>
<filter-class>org.apache.catalina.filters.ExpiresFilter</filter-class>
<init-param>
<param-name>ExpiresByType image</param-name>
<param-value>access plus 10 days</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>ExpiresFilter</filter-name>
<url-pattern>/*</url-pattern>
<dispatcher>REQUEST</dispatcher>
</filter-mapping>

You can find more details here

https://tomcat.apache.org/tomcat-7.0-doc/api/org/apache/catalina/filters/ExpiresFilter.html