Delegating Session Factory

Version 4.2 introduced the DelegatingSessionFactory, which allows the selection of the actual session factory at runtime. Prior to invoking the SFTP endpoint, you can call setThreadKey() on the factory to associate a key with the current thread. That key is then used to look up the actual session factory to be used. You can clear the key by calling clearThreadKey() after use.

We added convenience methods so that you can more easily do so from a message flow, as the following example shows:

<bean id="dsf" class="org.springframework.integration.file.remote.session.DelegatingSessionFactory">
    <constructor-arg>
        <bean class="o.s.i.file.remote.session.DefaultSessionFactoryLocator">
            <!-- delegate factories here -->
        </bean>
    </constructor-arg>
</bean>

<int:service-activator input-channel="in" output-channel="c1"
        expression="@dsf.setThreadKey(#root, headers['factoryToUse'])" />

<int-sftp:outbound-gateway request-channel="c1" reply-channel="c2" ... />

<int:service-activator input-channel="c2" output-channel="out"
        expression="@dsf.clearThreadKey(#root)" />

When using session caching (see SFTP Session Caching), each of the delegates should be cached. You cannot cache the DelegatingSessionFactory itself.

Starting with version 5.0.7, the DelegatingSessionFactory can be used in conjunction with a RotatingServerAdvice to poll multiple servers; see Inbound Channel Adapters: Polling Multiple Servers and Directories.