How to optimize with Last-Modified and Cache-Control?
Last Modified header
Section 14.29 of RFC2616|http://www.w3.org/Protocols/rfc2616/rfc2616.html] describes the last-modified header. If this header is sent with a response containing content, then the client is able to cache that content and check that it is up to date with a request containing a If-Modified-Since header.
If the content has not been modified, then a simple 304 response may be sent and the server can avoid resending the content.
Jetty will put a last-modified-header on all static content served and implements support for the if-modified-since header in the default servlet that serves that static content. For dynamic content generated by servlets, last-modified and if-modified-since may be supported by implementing the getLastModified(request) method on the servlet.