INT-4303: (S)FTP MGET with FileExistsMode.IGNORE

JIRA: https://jira.spring.io/browse/INT-4303

Don't emit ignored files in the output message payload.

Also, always preserve the timestamp when using `FileExistsMode.REPLACE_IF_MODIFIED`.

Some code style polishing

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

@@ -1039,12 +1039,18 @@ public abstract class AbstractRemoteFileOutboundGateway<F> extends AbstractReply
 			if (!appending && !tempFile.renameTo(localFile)) {
 				throw new MessagingException("Failed to rename local file");
 			}
-			if (this.options.contains(Option.PRESERVE_TIMESTAMP)) {
+			if (this.options.contains(Option.PRESERVE_TIMESTAMP)
+					|| FileExistsMode.REPLACE_IF_MODIFIED.equals(fileExistsMode)) {
 				localFile.setLastModified(getModified(fileInfo));
 			}
 		}
 		else if (FileExistsMode.REPLACE_IF_MODIFIED.equals(fileExistsMode)) {
-			logger.debug("Local file '" + localFile + "' has the same modified timestamp, ignored");
+			if (logger.isDebugEnabled()) {
+				logger.debug("Local file '" + localFile + "' has the same modified timestamp, ignored");
+			}
+			if (this.command.equals(Command.MGET)) {
+				localFile = null;
+			}
 		}
 		else if (!FileExistsMode.IGNORE.equals(fileExistsMode)) {
 			throw new MessageHandlingException(message, "Local file " + localFile + " already exists");
@@ -1053,6 +1059,9 @@ public abstract class AbstractRemoteFileOutboundGateway<F> extends AbstractReply
 			if (logger.isDebugEnabled()) {
 				logger.debug("Existing file skipped: " + localFile);
 			}
+			if (this.command.equals(Command.MGET)) {
+				localFile = null;
+			}
 		}
 		return localFile;
 	}
@@ -1098,9 +1107,10 @@ public abstract class AbstractRemoteFileOutboundGateway<F> extends AbstractReply
 				 */
 				String fileName = this.getRemoteFilename(fullFileName);
 				String actualRemoteDirectory = this.getRemoteDirectory(fullFileName, fileName);
-				File file = get(message, session, actualRemoteDirectory,
-						fullFileName, fileName, lsEntry.getFileInfo());
-				files.add(file);
+				File file = get(message, session, actualRemoteDirectory, fullFileName, fileName, lsEntry.getFileInfo());
+				if (file != null) {
+					files.add(file);
+				}
 			}
 		}
 		catch (Exception e) {
@@ -1141,9 +1151,10 @@ public abstract class AbstractRemoteFileOutboundGateway<F> extends AbstractReply
 				 */
 				String fileName = this.getRemoteFilename(fullFileName);
 				String actualRemoteDirectory = this.getRemoteDirectory(fullFileName, fileName);
-				File file = get(message, session, actualRemoteDirectory,
-						fullFileName, fileName, lsEntry.getFileInfo());
-				files.add(file);
+				File file = get(message, session, actualRemoteDirectory, fullFileName, fileName, lsEntry.getFileInfo());
+				if (file != null) {
+					files.add(file);
+				}
 			}
 		}
 		catch (Exception e) {

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

@@ -42,6 +42,7 @@
 							  command="mget"
 							  command-options="-f -P"
 							  expression="payload"
+							  mode="IGNORE"
 							  local-directory-expression="@extraConfig.targetLocalDirectoryName + (#remoteDirectory ?: '')"
 							  local-filename-generator-expression="#remoteFileName.replaceFirst('ftpSource', 'localTarget')"
 							  reply-channel="output"/>

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

@@ -228,6 +228,11 @@ public class FtpServerOutboundTests extends FtpTestSupport {
 		for (File file : localFiles) {
 			assertThat(file.getPath().replaceAll(Matcher.quoteReplacement(File.separator), "/"), containsString(dir));
 		}
+		this.inboundMGet.send(new GenericMessage<Object>(dir + "*.txt"));
+		result = this.output.receive(1000);
+		assertNotNull(result);
+		localFiles = (List<File>) result.getPayload();
+		assertThat(localFiles.size(), equalTo(0));
 	}
 
 	@Test

src/reference/asciidoc/ftp.adoc

@@ -886,7 +886,7 @@ You can either do that in your custom code, or route a copy of the message to a
 
 *mget*
 
-_mget_ retrieves multiple remote files based on a pattern and supports the following option:
+_mget_ retrieves multiple remote files based on a pattern and supports the following options:
 
 * -P - preserve the timestamps of the remote files
 
@@ -896,9 +896,13 @@ _mget_ retrieves multiple remote files based on a pattern and supports the follo
 
 The message payload resulting from an _mget_ operation is a `List<File>` object - a List of File objects, each representing a retrieved file.
 
+IMPORTANT: Startng with _version 5.0_, if the `FileExistsMode` is `IGNORE`, the payload of the output message will no longer contain files that were not fetched due to the file already existing.
+Previously, the array contained all files, including those that already existed.
+
 The expression used to determine the remote path should produce a result that ends with `*` - e.g. `foo/*` will fetch the complete tree under `foo`.
 
 Starting with _version 5.0_, a recursive `MGET`, combined with the new `FileExistsMode.REPLACE_IF_MODIFIED` mode, can be used to periodically synchronize an entire remote directory tree locally.
+This mode will set the local file last modified timestamp with the remote timestamp, regardless of the `-P` (preserve timestamp) option.
 
 .Notes for when using recursion (`-R`)
 [IMPORTANT]

src/reference/asciidoc/sftp.adoc

@@ -908,7 +908,7 @@ You can either do that in your custom code, or route a copy of the message to a
 
 *mget*
 
-_mget_ retrieves multiple remote files based on a pattern and supports the following option:
+_mget_ retrieves multiple remote files based on a pattern and supports the following options:
 
 * -P - preserve the timestamps of the remote files
 
@@ -918,9 +918,14 @@ _mget_ retrieves multiple remote files based on a pattern and supports the follo
 
 The message payload resulting from an _mget_ operation is a `List<File>` object - a List of File objects, each representing a retrieved file.
 
+IMPORTANT: Startng with _version 5.0_, if the `FileExistsMode` is `IGNORE`, the payload of the output message will no longer contain files that were not fetched due to the file already existing.
+Previously, the array contained all files, including those that already existed.
+
+
 The expression used to determine the remote path should produce a result that ends with `*` - e.g. `foo/*` will fetch the complete tree under `foo`.
 
 Starting with _version 5.0_, a recursive `MGET`, combined with the new `FileExistsMode.REPLACE_IF_MODIFIED` mode, can be used to periodically synchronize an entire remote directory tree locally.
+This mode will set the local file last modified timestamp to the remote file timestamp, regardless of the `-P` (preserve timestamp) option.
 
 .Notes for when using recursion (`-R`)
 [IMPORTANT]