FTP Session Caching

Starting with Spring Integration 3.0, sessions are no longer cached by default. The cache-sessions attribute is no longer supported on endpoints. You must use a CachingSessionFactory (shown in the next example) if you wish to cache sessions.

In versions prior to 3.0, the sessions were automatically cached by default. A cache-sessions attribute was available for disabling the auto caching, but that solution did not provide a way to configure other session caching attributes. For example, you could not limit the number of sessions created. To support that requirement and other configuration options, a CachingSessionFactory was added. It provides sessionCacheSize and sessionWaitTimeout properties. The sessionCacheSize property controls how many active sessions the factory maintains in its cache (the default is unbounded). If the sessionCacheSize threshold has been reached, any attempt to acquire another session blocks until either one of the cached sessions becomes available or until the wait time for a session expires (the default wait time is Integer.MAX_VALUE). The sessionWaitTimeout property configures that value.

If you want your sessions to be cached, configure your default session factory as described earlier and then wrap it in an instance of CachingSessionFactory, where you can provide those additional properties. The following example shows how to do so:

<bean id="ftpSessionFactory" class="o.s.i.ftp.session.DefaultFtpSessionFactory">
    <property name="host" value="localhost"/>
</bean>

<bean id="cachingSessionFactory" class="o.s.i.file.remote.session.CachingSessionFactory">
    <constructor-arg ref="ftpSessionFactory"/>
    <constructor-arg value="10"/>
    <property name="sessionWaitTimeout" value="1000"/>
</bean>

The preceding example shows a CachingSessionFactory created with the sessionCacheSize set to 10 and the sessionWaitTimeout set to one second (its value is in milliseconds).

Starting with Spring Integration 3.0, the CachingConnectionFactory provides a resetCache() method. When invoked, all idle sessions are immediately closed and in-use sessions are closed when they are returned to the cache. New requests for sessions establish new sessions as necessary.

Starting with version 5.1, the CachingSessionFactory has a new property testSession. When true, the session will be tested by sending a NOOP command to ensure it is still active; if not, it will be removed from the cache; a new session is created if no active sessions are in the cache.