question: public static void markCacheableForever ( HttpServletResponse response ) { long expiresAfterMillis = System . currentTimeMillis ( ) + ONE_YEAR_MILLIS ; response . setHeader ( ServletConstants . HTTP_PRAGMA , "" ) ; response . setDateHeader ( ServletConstants . HTTP_EXPIRES , expiresAfterMillis ) ; response . setHeader ( ServletConstants . HTTP_CACHE_CONTROL , ServletConstants . HTTP_CACHE_CONTROL_PRIVATE ) ; response . addHeader ( ServletConstants . HTTP_CACHE_CONTROL , ServletConstants . HTTP_CACHE_CONTROL_MAX_AGE + ONE_YEAR_MILLIS ) ; }
target:  Marks the resource returned to a web client to be stored in cache for a very long time. The resource is marked to be cached privately, i.e. on the client only, not in intermediate caches like proxies.