title: ShallowEtagHeaderFilter does not work under WAS8 app server
body: <p><code>org.springframework.web.filter.ShallowEtagHeaderFilter</code> is unable to set response header under WAS8 application server stating "<strong><em>WARNING: Cannot set header. Response already committed</em></strong>". However this works fine when tested under Tomcat server. <code>ShallowEtagHeaderFilter</code> is indeed wrapping the original response to delay the writing of response body, but still the response comes as committed after the filter chain's execution. Is this a possible websphere bug? Any suggestion / workaround to overcome this issue is welcome.</p>