INT-1664, INT-1665 added isOpen() method to the Session strategy, added check for stale connection to the CachingSessionFactory which will ensure that it only returns valid (non-stale) Session

spring-integration-sftp/src/main/java/org/springframework/integration/sftp/session/SftpSession.java

@@ -39,6 +39,7 @@ import com.jcraft.jsch.SftpException;
  * @author Josh Long
  * @author Mario Gray
  * @author Mark Fisher
+ * @author Oleg Zhurakousky
  * @since 2.0
  */
 class SftpSession implements Session {
@@ -136,4 +137,8 @@ class SftpSession implements Session {
 		}
 	}
 
+	public boolean isOpen() {
+		return this.channel.isConnected() && this.jschSession.isConnected();
+	}
+
 }