Apple WebObjects 3.5 - Manual (Page 135)

Controlling Component State
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At times, a user’s choice signals the end of a session (such as when the Yes
button is clicked in response to the query, “Do you really want to leave the
Intergalactic Web Mall?”). If you are sure a session has ended, you can send
a
terminate message to the session object, marking it (and the resources it
holds) for release.
A session marked for release won’t actually be released until the end of the
current request-response loop. Other objects may need to know whether a
particular request-response loop is their last, so they can close files or do
other clean up. They can learn their fate by sending the session object an
isTerminating message.
Using awake and sleep
Another strategy for managing session state is to create it at the beginning
of the request-response loop and then release it at the end. The session
object’s
awake and sleep methods provide the hooks you need to implement
this strategy. A session object receives an awake message at the beginning of
the request-response loop (where you can reinitialize the session state) and
a
sleep message at the end (where you can release it).
Controlling Component State
Component objects exist within a particular session and are stored along
with the session object between each cycle of the request-response loop.
Since a user can visit many pages during a session, managing component
state can be crucial to reducing your application’s storage requirements.
Managing Component Resources
Typically, page caching occurs both on the client machine and on the
WebObjects application server. WOApplication provides methods to
control caching on either end of a web connection. This section discusses
server-side caching and the section “Client-Side Page Caching” (page 139)
looks at the consequences of page caching on the client.
There are three common techniques for controlling component resources:
• Adjusting the page cache size
• Using awake and sleep to initialize and release resources
• Controlling page instantiation by implementing pageWithName: