Add Apache MINA SftpEventListener

- republish certain events as `ApplicationEvent`s.

* * Add ApacheMinaFtplet to provide the same functionality with FTP
* Fix typo

* * Polishing javadocs and event toString() methods

src/reference/asciidoc/event.adoc

@@ -55,6 +55,51 @@ In the preceding example, all application context events that match one of the t
 If a downstream component throws an exception, a `MessagingException` that contains the failed message and exception is sent to the channel named 'eventErrorChannel'.
 If no `error-channel` is specified and the downstream channels are synchronous, the exception is propagated to the caller.
 
+Using Java to configure the same adapter:
+
+====
+[source, java]
+----
+@Bean
+public ApplicationEventListeningMessageProducer eventsAdapter(
+            MessageChannel eventChannel, MessageChannel eventErrorChannel) {
+
+    ApplicationEventListeningMessageProducer producer =
+        new ApplicationEventListeningMessageProducer();
+    producer.setEventTypes(example.FooEvent.class, example.BarEvent.class, java.util.Date.class);
+    producer.setOutputChannel(eventChannel);
+    producer.setErrorChannel(eventErrorChannel);
+    return producer;
+}
+----
+====
+
+With the Java DSL:
+
+====
+[source, java]
+----
+@Bean
+public ApplicationEventListeningMessageProducer eventsAdapter() {
+
+    ApplicationEventListeningMessageProducer producer =
+        new ApplicationEventListeningMessageProducer();
+    producer.setEventTypes(example.FooEvent.class, example.BarEvent.class, java.util.Date.class);
+    return producer;
+}
+
+@Bean
+public IntegrationFlow eventFlow(ApplicationEventListeningMessageProducer eventsAdapter,
+        MessageChannel eventErrorChannel) {
+
+    return IntegrationFlows.from(eventsAdapter, e -> e.errorChannel(eventErrorChannel))
+        .handle(...)
+        ...
+        .get();
+}
+----
+====
+
 [[appevent-outbound]]
 === Sending Spring Application Events
 
@@ -72,7 +117,7 @@ For convenience, namespace support is provided to configure an `ApplicationEven
 ----
 ====
 
-If you use a `PollableChannel` (such as a `Queue`), you can also provide `poller` as a child element of the `outbound-channel-adapter` element.
+If you use a `PollableChannel` (such as a `QueueChannel`), you can also provide a `poller` child element of the `outbound-channel-adapter` element.
 You can also optionally provide a `task-executor` reference for that poller.
 The following example demonstrates both:
 
@@ -96,3 +141,40 @@ If the payload of the message is an `ApplicationEvent`, it is passed as-is.
 Otherwise, the message itself is wrapped in a `MessagingEvent` instance.
 
 Starting with version 4.2, you can configure the `ApplicationEventPublishingMessageHandler` (`<int-event:outbound-channel-adapter>`) with the `publish-payload` boolean attribute to publish to the application context `payload` as is, instead of wrapping it to a `MessagingEvent` instance.
+
+To configure the adapter using Java configuration:
+
+====
+[source, java]
+----
+@Bean
+@ServiceActivator(inputChannel = "eventChannel")
+public ApplicationEventPublishingMessageHandler eventHandler() {
+    ApplicationEventPublishingMessageHandler handler =
+            new ApplicationEventPublishingMessageHandler();
+    handler.setPublishPayload(true);
+    return handler;
+}
+----
+====
+
+With the Java DSL:
+
+====
+[source, java]
+----
+@Bean
+public ApplicationEventPublishingMessageHandler eventHandler() {
+    ApplicationEventPublishingMessageHandler handler =
+            new ApplicationEventPublishingMessageHandler();
+    handler.setPublishPayload(true);
+    return handler;
+}
+
+@Bean
+// MessageChannel is "eventsFlow.input"
+public IntegrationFlow eventsOutFlow(ApplicationEventPublishingMessageHandler eventHandler) {
+    return f -> f.handle(eventHandler);
+}
+----
+====

src/reference/asciidoc/ftp.adoc

@@ -1508,3 +1508,54 @@ When using XML configuration, the `<int-ftp:outbound-gateway/>` provides a `sess
 
 NOTE: The `session-callback` is mutually exclusive with the `command` and `expression` attributes.
 When configuring with Java, different constructors are available in the https://docs.spring.io/spring-integration/api/org/springframework/integration/ftp/gateway/FtpOutboundGateway.html[`FtpOutboundGateway`] class.
+
+[[ftp-server-events]]
+=== Apache Mina FTP Server Events
+
+The `ApacheMinaFtplet`, added in version 5.2, listens for certain Apache Mina FTP server events and publishes them as `ApplicationEvent` s which can be received by any `ApplicationListener` bean, `@EventListener` bean method, or <<./event.adoc#appevent-inbound, Event Inbound Channel Adapter>>.
+
+Currently supported events are:
+
+* `SessionOpenedEvent` - a client session was opened
+* `DirectoryCreatedEvent` - a directory was created
+* `FileWrittenEvent` - a file was written to
+* `PathMovedEvent` - a file or directory was renamed
+* `PathRemovedEvent` - a file or directory was removed
+* `SessionClosedEvent` - the client has disconnected
+
+Each of these is a subclass of `ApacheMinaFtpEvent`; you can configure a single listener to receive all of the event types.
+The `source` property of each event is a `FtpSession`, from which you can obtain information such as the client address; a convenient `getSession()` method is provided on the abstract event.
+
+Events other than session open/close have another property `FtpRequest` which has properties such as the command and arguments.
+
+To configure the server with the listener (which must be a Spring bean), add it to the server factory:
+
+====
+[source, java]
+----
+FtpServerFactory serverFactory = new FtpServerFactory();
+...
+ListenerFactory factory = new ListenerFactory();
+...
+serverFactory.addListener("default", factory.createListener());
+serverFactory.setFtplets(new HashMap<>(Collections.singletonMap("springFtplet", apacheMinaFtpletBean)));
+server = serverFactory.createServer();
+server.start();
+----
+====
+
+To consume these events using a Spring Integration event adapter:
+
+====
+[source, java]
+----
+@Bean
+public ApplicationEventListeningMessageProducer eventsAdapter() {
+    ApplicationEventListeningMessageProducer producer =
+        new ApplicationEventListeningMessageProducer();
+    producer.setEventTypes(ApacheMinaFtpEvent.class);
+    producer.setOutputChannel(eventChannel());
+    return producer;
+}
+----
+====

src/reference/asciidoc/sftp.adoc

@@ -1387,3 +1387,49 @@ When using XML configuration, the `<int-sftp:outbound-gateway/>` provides a `ses
 
 NOTE: The `session-callback` is mutually exclusive with the `command` and `expression` attributes.
 When configuring with Java, the `SftpOutboundGateway` class offers different constructors.
+
+[[sftp-server-events]]
+=== Apache Mina SFTP Server Events
+
+The `ApacheMinaSftpEventListener`, added in version 5.2, listens for certain Apache Mina SFTP server events and publishes them as `ApplicationEvent` s which can be received by any `ApplicationListener` bean, `@EventListener` bean method, or <<./event.adoc#appevent-inbound, Event Inbound Channel Adapter>>.
+
+Currently supported events are:
+
+* `SessionOpenedEvent` - a client session was opened
+* `DirectoryCreatedEvent` - a directory was created
+* `FileWrittenEvent` - a file was written to
+* `PathMovedEvent` - a file or directory was renamed
+* `PathRemovedEvent` - a file or directory was removed
+* `SessionClosedEvent` - the client has disconnected
+
+Each of these is a subclass of `ApacheMinaSftpEvent`; you can configure a single listener to receive all of the event types.
+The `source` property of each event is a `ServerSession`, from which you can obtain information such as the client address; a convenient `getSession()` method is provided on the abstract event.
+
+To configure the server with the listener (which must be a Spring bean), simply add it to the `SftpSubsystemFactory`:
+
+====
+[source, java]
+----
+server = SshServer.setUpDefaultServer();
+...
+SftpSubsystemFactory sftpFactory = new SftpSubsystemFactory();
+sftpFactory.addSftpEventListener(apacheMinaSftpEventListenerBean);
+...
+----
+====
+
+To consume these events using a Spring Integration event adapter:
+
+====
+[source, java]
+----
+@Bean
+public ApplicationEventListeningMessageProducer eventsAdapter() {
+    ApplicationEventListeningMessageProducer producer =
+        new ApplicationEventListeningMessageProducer();
+    producer.setEventTypes(ApacheMinaSftpEvent.class);
+    producer.setOutputChannel(eventChannel());
+    return producer;
+}
+----
+====

src/reference/asciidoc/whats-new.adoc

@@ -49,6 +49,12 @@ See <<./scripting.adoc#scripting,Scripting Support>> for more information.
 The `FluxAggregatorMessageHandler` is now available for grouping and windowing messages logic based on the Project Reactor `Flux` operators.
 See <<./aggregator.adoc#flux-aggregator,Flux Aggregator>> for more information.
 
+[[x5.2-sftp-events]]
+==== FTP/SFTP Event Publisher
+
+The FTP and SFTP modules now provide an event listener for certain Apache Mina FTP/SFTP server events.
+See <<./ftp.adoc#ftp-server-events, Apache Mina FTP Server Events>> and <<./sftp.adoc#sftp-server-events, Apache Mina SFTP Server Events>> for more information.
+
 [[x5.2-general]]
 === General Changes