Custom Session dirty logic

Fixes #2687

Allows any session to implement its dirty logic.

* License year was not updated

**Cherry-pick to 5.0.x**

Author: alturkovic

spring-integration-file/src/main/java/org/springframework/integration/file/remote/RemoteFileTemplate.java

@@ -56,6 +56,7 @@
  * @author David Turanski
  * @author Gary Russell
  * @author Artem Bilan
+ * @author Alen Turkovic
  *
  * @since 3.0
  *
@@ -442,9 +443,7 @@ public <T> T execute(SessionCallback<F, T> callback) {
 			return callback.doInSession(session);
 		}
 		catch (Exception e) {
-			if (session instanceof CachingSessionFactory<?>.CachedSession) {
-				((CachingSessionFactory.CachedSession) session).dirty();
-			}
+			session.dirty();
 			if (e instanceof MessagingException) {
 				throw (MessagingException) e;
 			}

spring-integration-file/src/main/java/org/springframework/integration/file/remote/session/CachingSessionFactory.java

@@ -36,6 +36,7 @@
  * @author Oleg Zhurakousky
  * @author Mark Fisher
  * @author Gary Russell
+ * @author Alen Turkovic
  * @since 2.0
  */
 public class CachingSessionFactory<F> implements SessionFactory<F>, DisposableBean {
@@ -284,6 +285,7 @@ public boolean finalizeRaw() throws IOException {
 			return this.targetSession.finalizeRaw();
 		}
 
+		@Override
 		public void dirty() {
 			this.dirty = true;
 		}

spring-integration-file/src/main/java/org/springframework/integration/file/remote/session/Session.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,6 +29,7 @@
  * @author Mark Fisher
  * @author Oleg Zhurakousky
  * @author Gary Russell
+ * @author Alen Turkovic
  * @since 2.0
  */
 public interface Session<F> extends Closeable {
@@ -117,4 +118,14 @@ default boolean test() {
 		return this.isOpen();
 	}
 
+	/**
+	 * Mark this session as dirty, indicating that it should not be reused and any
+	 * delegated sessions should be taken care of before closing.
+	 * @see CachingSessionFactory.CachedSession#close()
+	 * @since 5.1.2
+	 */
+	default void dirty() {
+		// NOOP
+	}
+
 }