How to disable ETag headers in Tomcat

Question

Tomcat seems to send an ETag header with each response by default. I'd like to disable these for reasons outlined here. I know I can strip them out in my Apache configuration, but is there any way to disable them on the Tomcat side?

Answer 1

No way disable out of the box. But ETags are set by the DefaultServlet via request.setHeader(). So an easy workaround to disable them is to create a filter for DefaultServlet which swallows the tag. For example:

void doFilter(ServletRequest request, ServletRequest reponse) {
  chain.doFilter(request, new HttpServletResponseWrapper(response) {
      public void setHeader(String name, String value) {
          if (!"etag".equalsIgnoreCase(name)) {
              super.setHeader(name, value);
          }
      }
  });
}

And in web.xml:

  <filter>
    <filter-name>noetag</filter-name>
    <filter-class>foo.NoEtagFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>noetag</filter-name>
    <servlet-name>default</servlet-name>
    <dispatcher>REQUEST</dispatcher>
    <dispatcher>FORWARD</dispatcher>
  </filter-mapping>