Tracks the usage of a page instance, allowing a last access property to be associated with the page. CachedPage instances are only accessed from within a {@link org.apache.tapestry5.internal.services.PagePoolCache}, which handles synchronization concerns.
An earlier version of this code used
soft references, but those seem to be problematic (the test suite started behaving erratically and response time suffered). Perhaps that could be addressed via tuning of the VM, but for the meantime, we use hard references and rely more on the soft and hard limits and the culling of unused pages periodically.