uPortal supports all of the JSR-168 and JSR-286 caching features.
Expiration Based Caching
Portlets can specify an expiration timeout, in seconds, in their portlet.xml or via a response property or via the CacheControl API. When an expiration time is set the portal will return the cached content for the portlet until the expiration time passes OR until the user directly interacts with the portlet.
Validation (ETag) Caching
Portlets can specify an ETag along with expiration time on render and resource responses which are used to represent the state of the response. Subsequent requests with the ETag and the portlet can simply respond that the cached content is still good. Validation caching also allows the portlet to mark specific responses as public or private scoped, publicly scoped data may be shared between multiple users.
uPortal takes these ETag related features as far as possible to improve performance with resource responses getting the biggest benefit.
- When a portlet sets an ETag on any response with an expiration time the portal caches the content using the ETag, until the expiration time passes any subsequent request for the same ETag results in immediate replay from cache
- One the expiration time for an ETagged response has passed the portlet is consulted to see if the ETag is still valid for the request, if the portlet returns true the content is replayed and the cache expiration updated.
- On resource responses the ETag is passed to the browser as the ETag HTTP header and the expiration time is passed as the
More Information
For a complete description of how portlet caching works it is recommended to read section PLT.22 of the JSR-286 specification.