FTP Session Caching

从 Spring Integration 3.0 开始，不再默认缓存会话。端点上不再支持 cache-sessions 特性。如果您希望缓存会话，您必须使用 CachingSessionFactory（在随后的示例中展示）。

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.

在 3.0之前的版本中，会话默认情况下会自动缓存。cache-sessions 属性可用于禁用自动缓存，但该解决方案并没有提供一种配置其他会话缓存属性的方法。例如，你无法限制创建的会话数。为了支持该要求和其他配置选项，添加了 CachingSessionFactory。它提供 sessionCacheSize 和 sessionWaitTimeout 属性。sessionCacheSize 属性控制工厂在其缓存中维护多少个活动会话（默认情况下无限制）。如果已达到 sessionCacheSize 阈值，则获取另一个会话的任何尝试都将阻塞，直到其中一个缓存会话变为可用或会话等待时间到期（默认等待时间为 Integer.MAX_VALUE）。sessionWaitTimeout 属性配置该值。

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.

如果希望缓存会话，请按前面所述配置你的默认会话工厂，然后将其包装在 CachingSessionFactory 实例中，你可以在其中提供这些附加属性。以下示例演示如何执行此操作：

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>

前一个示例显示了创建一个 CachingSessionFactory，其中 sessionCacheSize 设置为 10，sessionWaitTimeout 设置为一秒（其值为毫秒）。

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).

从 Spring Integration 3.0 开始，CachingConnectionFactory 提供了 resetCache() 方法。调用时，所有空闲会话都会立即关闭，而正在使用的会话会在返回到缓存时关闭。对会话的新请求将根据需要建立新的会话。

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.

自版本 5.1 起，CachingSessionFactory 有一个新特性 testSession。为 true 时，会话会通过发送 NOOP 命令来经过测试，以确保它依然活跃；如果不活跃，它会从缓存中移除；如果没有活跃会话存在于缓存中，将会创建一个新会话。

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.