INT-3737: (S)FTP Outbound Gateway Streaming GET

JIRA: https://jira.spring.io/browse/INT-3737

Support returning an `InputStream` from a GET operation.

This can be used in conjuction with a `<file:splitter/>` to stream a text file.

The user is responsible for releasing the session when the download is complete.

The session object is stored in the message header and `RemoteFileUtils.closeSession()` should be called
to clean up and close the session.

INT-3737: Polishing and Docs

Fix `CachedSession.close()` bug

Preventing `Caused by: java.io.IOException: Previous raw read was not finalized`
when `Session` is returned to the pool, but `readingRaw` hasn't been finalized
because the real `close()` isn't invoked in case of normal return to pool.

spring-integration-file/src/main/java/org/springframework/integration/file/FileHeaders.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -35,6 +35,8 @@ public abstract class FileHeaders {
 
 	public static final String REMOTE_FILE = PREFIX + "remoteFile";
 
+	public static final String REMOTE_SESSION = PREFIX + "remoteSession";
+
 	public static final String RENAME_TO = PREFIX + "renameTo";
 
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2014 the original author or authors.
+ * Copyright 2013-2015 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.
@@ -98,6 +98,14 @@ public class RemoteFileTemplate<F> implements RemoteFileOperations<F>, Initializ
 		this.sessionFactory = sessionFactory;
 	}
 
+	/**
+	 * @return this template's {@link SessionFactory}.
+	 * @since 4.2
+	 */
+	public SessionFactory<F> getSessionFactory() {
+		return sessionFactory;
+	}
+
 	/**
 	 * Determine whether the remote directory should automatically be created when
 	 * sending files to the remote system.

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

@@ -40,12 +40,14 @@ import org.springframework.integration.file.FileHeaders;
 import org.springframework.integration.file.filters.FileListFilter;
 import org.springframework.integration.file.remote.AbstractFileInfo;
 import org.springframework.integration.file.remote.RemoteFileTemplate;
+import org.springframework.integration.file.remote.RemoteFileUtils;
 import org.springframework.integration.file.remote.SessionCallback;
 import org.springframework.integration.file.remote.session.Session;
 import org.springframework.integration.file.remote.session.SessionFactory;
 import org.springframework.integration.file.support.FileExistsMode;
 import org.springframework.integration.handler.AbstractReplyProducingMessageHandler;
 import org.springframework.integration.handler.ExpressionEvaluatingMessageProcessor;
+import org.springframework.integration.support.AbstractIntegrationMessageBuilder;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHandlingException;
 import org.springframework.messaging.MessagingException;
@@ -170,7 +172,12 @@ public abstract class AbstractRemoteFileOutboundGateway<F> extends AbstractReply
 		/**
 		 * Recursive (ls, mget)
 		 */
-		RECURSIVE("-R");
+		RECURSIVE("-R"),
+
+		/**
+		 * Streaming 'get' (returns InputStream); user must call {@link RemoteFileUtils#closeSession(Session)}.
+		 */
+		STREAM("-stream");
 
 		private String option;
 
@@ -364,7 +371,7 @@ public abstract class AbstractRemoteFileOutboundGateway<F> extends AbstractReply
 				Command.GET.equals(this.command)) {
 			Assert.isNull(this.filter, "Filters are not supported with the rm and get commands");
 		}
-		if (Command.GET.equals(this.command)
+		if ((Command.GET.equals(this.command) && !options.contains(Option.STREAM))
 				|| Command.MGET.equals(this.command)) {
 			Assert.notNull(this.localDirectoryExpression, "localDirectory must not be null");
 			if (this.localDirectoryExpression instanceof LiteralExpression) {
@@ -449,19 +456,37 @@ public abstract class AbstractRemoteFileOutboundGateway<F> extends AbstractReply
 		final String remoteFilePath =  this.fileNameProcessor.processMessage(requestMessage);
 		final String remoteFilename = this.getRemoteFilename(remoteFilePath);
 		final String remoteDir = this.getRemoteDirectory(remoteFilePath, remoteFilename);
-		File payload = this.remoteFileTemplate.execute(new SessionCallback<F, File>() {
-
-			@Override
-			public File doInSession(Session<F> session) throws IOException {
-				return AbstractRemoteFileOutboundGateway.this.get(requestMessage, session, remoteDir, remoteFilePath,
-						remoteFilename, true);
-
+		Session<F> session = null;
+		Object payload;
+		if (this.options.contains(Option.STREAM)) {
+			session = this.remoteFileTemplate.getSessionFactory().getSession();
+			try {
+				payload = session.readRaw(remoteFilePath);
 			}
-		});
-		return this.getMessageBuilderFactory().withPayload(payload)
+			catch (IOException e) {
+				throw new MessageHandlingException(requestMessage, "Failed to get the remote file ["
+						+ remoteFilePath
+						+ "] as a stream", e);
+			}
+		}
+		else {
+			payload = this.remoteFileTemplate.execute(new SessionCallback<F, File>() {
+
+				@Override
+				public File doInSession(Session<F> session) throws IOException {
+					return AbstractRemoteFileOutboundGateway.this.get(requestMessage, session, remoteDir, remoteFilePath,
+							remoteFilename, true);
+
+				}
+			});
+		}
+		AbstractIntegrationMessageBuilder<Object> builder = this.getMessageBuilderFactory().withPayload(payload)
 			.setHeader(FileHeaders.REMOTE_DIRECTORY, remoteDir)
-			.setHeader(FileHeaders.REMOTE_FILE, remoteFilename)
-			.build();
+			.setHeader(FileHeaders.REMOTE_FILE, remoteFilename);
+		if (session != null) {
+			builder.setHeader(FileHeaders.REMOTE_SESSION, session);
+		}
+		return builder.build();
 	}
 
 	private Object doMget(final Message<?> requestMessage) {

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

@@ -190,7 +190,15 @@ public class CachingSessionFactory<F> implements SessionFactory<F>, DisposableBe
 				else if (this.dirty) {
 					this.targetSession.close();
 				}
-				pool.releaseItem(targetSession);
+				if (this.targetSession.isOpen()) {
+					try {
+						this.targetSession.finalizeRaw();
+					}
+					catch (IOException e) {
+						//No-op in this context
+					}
+				}
+				pool.releaseItem(this.targetSession);
 				released = true;
 			}
 		}

spring-integration-file/src/main/java/org/springframework/integration/file/splitter/FileSplitter.java

@@ -38,6 +38,7 @@ import org.springframework.integration.file.splitter.FileSplitter.FileMarker.Mar
 import org.springframework.integration.splitter.AbstractMessageSplitter;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHandlingException;
+import org.springframework.util.StringUtils;
 
 /**
  * The {@link AbstractMessageSplitter} implementation to split the {@link File}
@@ -147,11 +148,11 @@ public class FileSplitter extends AbstractMessageSplitter {
 			else {
 				reader = new InputStreamReader((InputStream) payload, this.charset);
 			}
-			filePath = ":stream:";
+			filePath = buildPathFromMessage(message, ":stream:");
 		}
 		else if (payload instanceof Reader) {
 			reader = (Reader) payload;
-			filePath = ":reader:";
+			filePath = buildPathFromMessage(message, ":reader:");
 		}
 		else {
 			return message;
@@ -242,7 +243,6 @@ public class FileSplitter extends AbstractMessageSplitter {
 		}
 	}
 
-
 	@Override
 	protected boolean willAddHeaders(Message<?> message) {
 		Object payload = message.getPayload();
@@ -268,6 +268,17 @@ public class FileSplitter extends AbstractMessageSplitter {
 		}
 	}
 
+	private String buildPathFromMessage(Message<?> message, String defaultPath) {
+		String remoteDir = (String) message.getHeaders().get(FileHeaders.REMOTE_DIRECTORY);
+		String remoteFile = (String) message.getHeaders().get(FileHeaders.REMOTE_FILE);
+		if (StringUtils.hasText(remoteDir) && StringUtils.hasText(remoteFile)) {
+			return remoteDir + remoteFile;
+		}
+		else {
+			return defaultPath;
+		}
+	}
+
 	public static class FileMarker implements Serializable {
 
 		private static final long serialVersionUID = 8514605438145748406L;

spring-integration-ftp/src/main/java/org/springframework/integration/ftp/session/FtpSession.java

@@ -144,6 +144,9 @@ public class FtpSession implements Session<FTPFile> {
 	@Override
 	public void close() {
 		try {
+			if (this.readingRaw.get()) {
+				finalizeRaw();
+			}
 			this.client.disconnect();
 		}
 		catch (Exception e) {

spring-integration-ftp/src/test/java/org/springframework/integration/ftp/TestFtpServer.java

@@ -24,6 +24,7 @@ import java.util.Arrays;
 import javax.annotation.PostConstruct;
 import javax.annotation.PreDestroy;
 
+import org.apache.commons.net.ftp.FTPFile;
 import org.apache.ftpserver.FtpServer;
 import org.apache.ftpserver.FtpServerFactory;
 import org.apache.ftpserver.ftplet.Authentication;
@@ -40,6 +41,8 @@ import org.junit.rules.TemporaryFolder;
 
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.integration.file.remote.session.CachingSessionFactory;
+import org.springframework.integration.file.remote.session.SessionFactory;
 import org.springframework.integration.ftp.session.DefaultFtpSessionFactory;
 import org.springframework.integration.test.util.SocketUtils;
 
@@ -149,13 +152,14 @@ public class TestFtpServer {
 	}
 
 	@Bean
-	public DefaultFtpSessionFactory ftpSessionFactory() {
+	public SessionFactory<FTPFile> ftpSessionFactory() {
 		DefaultFtpSessionFactory factory = new DefaultFtpSessionFactory();
 		factory.setHost("localhost");
 		factory.setPort(this.ftpPort);
 		factory.setUsername("foo");
 		factory.setPassword("foo");
-		return factory;
+
+		return new CachingSessionFactory<FTPFile>(factory);
 	}
 
 	@PostConstruct

spring-integration-ftp/src/test/java/org/springframework/integration/ftp/outbound/FtpServerOutboundTests-context.xml

@@ -1,12 +1,13 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <beans xmlns="http://www.springframework.org/schema/beans"
-	   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-	   xmlns:int-ftp="http://www.springframework.org/schema/integration/ftp"
-	   xmlns:int="http://www.springframework.org/schema/integration"
-	   xsi:schemaLocation="http://www.springframework.org/schema/integration/ftp
-	 http://www.springframework.org/schema/integration/ftp/spring-integration-ftp.xsd
-		http://www.springframework.org/schema/integration http://www.springframework.org/schema/integration/spring-integration.xsd
-		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:int-ftp="http://www.springframework.org/schema/integration/ftp"
+	xmlns:int="http://www.springframework.org/schema/integration"
+	xmlns:int-file="http://www.springframework.org/schema/integration/file"
+	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
+		http://www.springframework.org/schema/integration/file http://www.springframework.org/schema/integration/file/spring-integration-file.xsd
+		http://www.springframework.org/schema/integration/ftp http://www.springframework.org/schema/integration/ftp/spring-integration-ftp.xsd
+		http://www.springframework.org/schema/integration http://www.springframework.org/schema/integration/spring-integration.xsd">
 
 	<bean id="ftpServer" class="org.springframework.integration.ftp.TestFtpServer">
 		<constructor-arg value="FtpServerOutboundTests"/>
@@ -104,6 +105,25 @@
 							  remote-directory="ftpTarget"
 							  reply-channel="output"/>
 
+	<int-ftp:outbound-gateway session-factory="ftpSessionFactory"
+							  request-channel="inboundGetStream"
+							  command="get"
+							  command-options="-stream"
+							  expression="payload"
+							  remote-directory="ftpTarget"
+							  reply-channel="stream" />
+
+	<int:chain input-channel="stream">
+		<int-file:splitter markers="true" />
+		<int:payload-type-router resolution-required="false" default-output-channel="output">
+			<int:mapping type="org.springframework.integration.file.splitter.FileSplitter$FileMarker"
+						 channel="markers" />
+		</int:payload-type-router>
+	</int:chain>
+
+	<int:service-activator input-channel="markers"
+	  expression="payload.mark.toString().equals('END') ? headers['file_remoteSession'].close() : null"/>
+
 	<int:channel id="appending" />
 
 	<int-ftp:outbound-channel-adapter id="appender"

spring-integration-ftp/src/test/java/org/springframework/integration/ftp/outbound/FtpServerOutboundTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 the original author or authors.
+ * Copyright 2013-2015 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.
@@ -21,7 +21,9 @@ import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.not;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
@@ -32,6 +34,7 @@ import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.apache.commons.net.ftp.FTPFile;
 import org.hamcrest.Matchers;
@@ -48,10 +51,11 @@ import org.springframework.integration.file.remote.InputStreamCallback;
 import org.springframework.integration.file.remote.RemoteFileTemplate;
 import org.springframework.integration.file.remote.SessionCallback;
 import org.springframework.integration.file.remote.session.Session;
+import org.springframework.integration.file.remote.session.SessionFactory;
 import org.springframework.integration.ftp.TestFtpServer;
-import org.springframework.integration.ftp.session.DefaultFtpSessionFactory;
 import org.springframework.integration.ftp.session.FtpRemoteFileTemplate;
 import org.springframework.integration.support.MessageBuilder;
+import org.springframework.integration.test.util.TestUtils;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessagingException;
 import org.springframework.messaging.PollableChannel;
@@ -74,7 +78,7 @@ public class FtpServerOutboundTests {
 	private TestFtpServer ftpServer;
 
 	@Autowired
-	private DefaultFtpSessionFactory ftpSessionFactory;
+	private SessionFactory<FTPFile> ftpSessionFactory;
 
 	@Autowired
 	private PollableChannel output;
@@ -112,6 +116,9 @@ public class FtpServerOutboundTests {
 	@Autowired
 	private DirectChannel failing;
 
+	@Autowired
+	private DirectChannel inboundGetStream;
+
 	@Before
 	public void setup() {
 		this.ftpServer.recursiveDelete(ftpServer.getTargetLocalDirectory());
@@ -342,6 +349,33 @@ public class FtpServerOutboundTests {
 
 	}
 
+	@Test
+	public void testStream() {
+		String dir = "ftpSource/";
+		this.inboundGetStream.send(new GenericMessage<Object>(dir + "ftpSource1.txt"));
+		Message<?> result = this.output.receive(1000);
+		assertNotNull(result);
+		assertEquals("source1", result.getPayload());
+		assertEquals("ftpSource/", result.getHeaders().get(FileHeaders.REMOTE_DIRECTORY));
+		assertEquals("ftpSource1.txt", result.getHeaders().get(FileHeaders.REMOTE_FILE));
+
+		Session<?> session = (Session<?>) result.getHeaders().get(FileHeaders.REMOTE_SESSION);
+		// Returned to cache
+		assertTrue(session.isOpen());
+		// Raw reading is finished
+		assertFalse(TestUtils.getPropertyValue(session, "targetSession.readingRaw", AtomicBoolean.class).get());
+
+		// Check that we can use the same session from cache to read another remote InputStream
+		this.inboundGetStream.send(new GenericMessage<Object>(dir + "ftpSource2.txt"));
+		result = this.output.receive(1000);
+		assertNotNull(result);
+		assertEquals("source2", result.getPayload());
+		assertEquals("ftpSource/", result.getHeaders().get(FileHeaders.REMOTE_DIRECTORY));
+		assertEquals("ftpSource2.txt", result.getHeaders().get(FileHeaders.REMOTE_FILE));
+		assertSame(TestUtils.getPropertyValue(session, "targetSession"),
+				TestUtils.getPropertyValue(result.getHeaders().get(FileHeaders.REMOTE_SESSION), "targetSession"));
+	}
+
 	private void assertLength6(FtpRemoteFileTemplate template) {
 		FTPFile[] files = template.execute(new SessionCallback<FTPFile, FTPFile[]>() {
 

spring-integration-ftp/src/test/java/org/springframework/integration/ftp/session/FtpRemoteFileTemplateTests.java

@@ -61,7 +61,7 @@ public class FtpRemoteFileTemplateTests {
 	private TestFtpServer ftpServer;
 
 	@Autowired
-	private DefaultFtpSessionFactory sessionFactory;
+	private SessionFactory<FTPFile> sessionFactory;
 
 	@Before
 	@After

spring-integration-sftp/src/test/java/org/springframework/integration/sftp/outbound/SftpServerOutboundTests-context.xml

@@ -1,12 +1,13 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <beans xmlns="http://www.springframework.org/schema/beans"
-	   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-	   xmlns:int-sftp="http://www.springframework.org/schema/integration/sftp"
-	   xmlns:int="http://www.springframework.org/schema/integration"
-	   xsi:schemaLocation="http://www.springframework.org/schema/integration/sftp
-	 http://www.springframework.org/schema/integration/sftp/spring-integration-sftp.xsd
-		http://www.springframework.org/schema/integration http://www.springframework.org/schema/integration/spring-integration.xsd
-		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:int-sftp="http://www.springframework.org/schema/integration/sftp"
+	xmlns:int="http://www.springframework.org/schema/integration"
+	xmlns:int-file="http://www.springframework.org/schema/integration/file"
+	xsi:schemaLocation="http://www.springframework.org/schema/integration/sftp http://www.springframework.org/schema/integration/sftp/spring-integration-sftp.xsd
+		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
+		http://www.springframework.org/schema/integration/file http://www.springframework.org/schema/integration/file/spring-integration-file.xsd
+		http://www.springframework.org/schema/integration http://www.springframework.org/schema/integration/spring-integration.xsd">
 
 	<int:channel id="output">
 		<int:queue/>
@@ -133,4 +134,23 @@
 							  auto-create-directory="true"
 							  remote-file-separator="/"	/>
 
+	<int-sftp:outbound-gateway session-factory="sftpSessionFactory"
+							  request-channel="inboundGetStream"
+							  command="get"
+							  command-options="-stream"
+							  expression="payload"
+							  remote-directory="ftpTarget"
+							  reply-channel="stream" />
+
+	<int:chain input-channel="stream">
+		<int-file:splitter markers="true" />
+		<int:payload-type-router resolution-required="false" default-output-channel="output">
+			<int:mapping type="org.springframework.integration.file.splitter.FileSplitter$FileMarker"
+						 channel="markers" />
+		</int:payload-type-router>
+	</int:chain>
+
+	<int:service-activator input-channel="markers"
+	  expression="payload.mark.toString().equals('END') ? headers['file_remoteSession'].close() : null"/>
+
 </beans>

spring-integration-sftp/src/test/java/org/springframework/integration/sftp/outbound/SftpServerOutboundTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2014 the original author or authors.
+ * Copyright 2013-2015 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.
@@ -21,6 +21,7 @@ import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.not;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertThat;
@@ -125,6 +126,9 @@ public class SftpServerOutboundTests {
 	@Autowired
 	private TestSftpServer sftpServer;
 
+	@Autowired
+	private DirectChannel inboundGetStream;
+
 	@Before
 	@After
 	public void setup() {
@@ -404,6 +408,18 @@ public class SftpServerOutboundTests {
 
 	}
 
+	@Test
+	public void testStream() {
+		String dir = "sftpSource/";
+		this.inboundGetStream.send(new GenericMessage<Object>(dir + "sftpSource1.txt"));
+		Message<?> result = this.output.receive(1000);
+		assertNotNull(result);
+		assertEquals("source1", result.getPayload());
+		assertEquals("sftpSource/", result.getHeaders().get(FileHeaders.REMOTE_DIRECTORY));
+		assertEquals("sftpSource1.txt", result.getHeaders().get(FileHeaders.REMOTE_FILE));
+		assertFalse(((Session<?>) result.getHeaders().get(FileHeaders.REMOTE_SESSION)).isOpen());
+	}
+
 	private void assertLength6(SftpRemoteFileTemplate template) {
 		LsEntry[] files = template.execute(new SessionCallback<LsEntry, LsEntry[]>() {
 

src/reference/asciidoc/ftp.adoc

@@ -328,10 +328,44 @@ _get_ retrieves a remote file and supports the following option:
 
 * -P - preserve the timestamp of the remote file
 
-The message payload resulting from a _get_ operation is a `File` object representing the retrieved file.
+* -stream - retrieve the remote file as a stream.
 
 The remote directory is provided in the `file_remoteDirectory` header, and the filename is provided in the `file_remoteFile` header.
 
+The message payload resulting from a _get_ operation is a `File` object representing the retrieved file, or
+an `InputStream` when the `-stream` option is provided.
+This option allows retrieving the file as a stream.
+For text files, a common use case is to combine this operation with a <<file-splitter>>.
+When consuming remote files as streams, the user is responsible for closing the `Session` after the stream is
+consumed.
+For convenience, the `Session` is provided in the `file_remoteSession` header.
+
+The following shows an example of consuming a file as a stream:
+
+[source, xml]
+----
+<int-ftp:outbound-gateway session-factory="ftpSessionFactory"
+							request-channel="inboundGetStream"
+							command="get"
+							command-options="-stream"
+							expression="payload"
+							remote-directory="ftpTarget"
+							reply-channel="stream" />
+
+<int:chain input-channel="stream">
+	<int-file:splitter markers="true" />
+	<int:payload-type-router resolution-required="false" default-output-channel="output">
+		<int:mapping type="org.springframework.integration.file.splitter.FileSplitter$FileMarker"
+					channel="markers" />
+	</int:payload-type-router>
+</int:chain>
+
+<int:service-activator input-channel="markers"
+	expression="payload.mark.toString().equals('END') ? headers['file_remoteSession'].close() : null"/>
+----
+
+The file lines are sent to the channel `output`.
+
 *mget*
 
 _mget_ retrieves multiple remote files based on a pattern and supports the following option:

src/reference/asciidoc/sftp.adoc

@@ -391,10 +391,44 @@ _get_ retrieves a remote file and supports the following option:
 
 * -P - preserve the timestamp of the remote file
 
-The message payload resulting from a _get_ operation is a `File` object representing the retrieved file.
+* -stream - retrieve the remote file as a stream.
 
 The remote directory is provided in the `file_remoteDirectory` header, and the filename is provided in the `file_remoteFile` header.
 
+The message payload resulting from a _get_ operation is a `File` object representing the retrieved file, or
+an `InputStream` when the `-stream` option is provided.
+This option allows retrieving the file as a stream.
+For text files, a common use case is to combine this operation with a <<file-splitter>>.
+When consuming remote files as streams, the user is responsible for closing the `Session` after the stream is
+consumed.
+For convenience, the `Session` is provided in the `file_remoteSession` header.
+
+The following shows an example of consuming a file as a stream:
+
+[source, xml]
+----
+<int-sftp:outbound-gateway session-factory="sftpSessionFactory"
+              request-channel="inboundGetStream"
+              command="get"
+              command-options="-stream"
+              expression="payload"
+              remote-directory="ftpTarget"
+              reply-channel="stream" />
+
+<int:chain input-channel="stream">
+  <int-file:splitter markers="true" />
+  <int:payload-type-router resolution-required="false" default-output-channel="output">
+    <int:mapping type="org.springframework.integration.file.splitter.FileSplitter$FileMarker"
+           channel="markers" />
+  </int:payload-type-router>
+</int:chain>
+
+<int:service-activator input-channel="markers"
+  expression="payload.mark.toString().equals('END') ? headers['file_remoteSession'].close() : null"/>
+----
+
+The file lines are sent to the channel `output`.
+
 *mget*
 
 _mget_ retrieves multiple remote files based on a pattern and supports the following option:

src/reference/asciidoc/whats-new.adoc

@@ -160,3 +160,9 @@ metadata store if it implements `Flushable` (e.g. the `PropertiesPersistenMetada
 
 When using Java 8, gateway methods can now return `CompletableFuture<?>`.
 See <<gw-completable-future>> for more information.
+
+[[x4.2-ftp-changes]]
+==== (S)FTP Changes
+
+The SFTP/FTP outbound gateway `get` operations now support the `-stream` option, allowing files to be retrieved as
+a stream. See <<ftp-outbound-gateway>> and <<sftp-outbound-gateway>> for more information.