Some code clean up for RemoteFileOutboundGateway

* Also apply suggested by IDE refactoring to `FtpServerOutboundTests`

Author: artembilan

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

@@ -151,8 +151,8 @@ public AbstractRemoteFileOutboundGateway(RemoteFileTemplate<F> remoteFileTemplat
 	}
 
 	/**
-	 * Construct an instance with the supplied session factory, a command ('ls', 'get'
-	 * etc), and an expression to determine the filename.
+	 * Construct an instance with the supplied session factory,
+	 * a command ('ls', 'get' etc.), and an expression to determine the filename.
 	 * @param sessionFactory the session factory.
 	 * @param command the command.
 	 * @param expression the filename expression.
@@ -164,8 +164,8 @@ public AbstractRemoteFileOutboundGateway(SessionFactory<F> sessionFactory, Strin
 	}
 
 	/**
-	 * Construct an instance with the supplied session factory, a command ('ls', 'get'
-	 * etc), and an expression to determine the filename.
+	 * Construct an instance with the supplied session factory,
+	 * a command ('ls', 'get' etc.), and an expression to determine the filename.
 	 * @param sessionFactory the session factory.
 	 * @param command the command.
 	 * @param expression the filename expression.
@@ -178,8 +178,8 @@ public AbstractRemoteFileOutboundGateway(SessionFactory<F> sessionFactory, Comma
 	}
 
 	/**
-	 * Construct an instance with the supplied remote file template, a command ('ls',
-	 * 'get' etc), and an expression to determine the filename.
+	 * Construct an instance with the supplied remote file template,
+	 * a command ('ls', 'get' etc.), and an expression to determine the filename.
 	 * @param remoteFileTemplate the remote file template.
 	 * @param command the command.
 	 * @param expression the filename expression.
@@ -191,8 +191,8 @@ public AbstractRemoteFileOutboundGateway(RemoteFileTemplate<F> remoteFileTemplat
 	}
 
 	/**
-	 * Construct an instance with the supplied remote file template, a command ('ls',
-	 * 'get' etc), and an expression to determine the filename.
+	 * Construct an instance with the supplied remote file template,
+	 * a command ('ls', 'get' etc.), and an expression to determine the filename.
 	 * @param remoteFileTemplate the remote file template.
 	 * @param command the command.
 	 * @param expressionArg the filename expression.
@@ -823,7 +823,7 @@ private String doPut(Message<?> requestMessage, String subDirectory) {
 	 * The session argument isn't used in the default implementation.
 	 * @param message the request message related to this put command
 	 * @param session the remote protocol session related to this invocation context
-	 * @param subDirectory the target sub directory to put
+	 * @param subDirectory the target sub-directory to put
 	 * @return The remote path, or null if no local file was found.
 	 * @since 5.0
 	 */
@@ -854,19 +854,19 @@ protected void doChmod(RemoteFileOperations<F> remoteFileOperations, String path
 	private Object doMput(Message<?> requestMessage) {
 		File file = null;
 		Object payload = requestMessage.getPayload();
-		if (payload instanceof File) {
-			file = (File) payload;
+		if (payload instanceof File filePayload) {
+			file = filePayload;
 		}
-		else if (payload instanceof String) {
-			file = new File((String) payload);
+		else if (payload instanceof String fileName) {
+			file = new File(fileName);
 		}
 		else if (!(payload instanceof Collection)) {
 			throw new IllegalArgumentException(
 					"Only File or String payloads (or Collection of File/String) allowed for 'mput', received: "
 							+ payload.getClass());
 		}
-		if ((payload instanceof Collection)) {
-			return ((Collection<?>) payload).stream()
+		if (payload instanceof Collection<?> files) {
+			return files.stream()
 					.map(p -> doMput(new MutableMessage<>(p, requestMessage.getHeaders())))
 					.collect(Collectors.toList());
 		}
@@ -926,7 +926,7 @@ else if (this.options.contains(Option.RECURSIVE)) {
 	private RuntimeException handlePutException(Message<?> requestMessage, String subDirectory,
 			List<File> filteredFiles, List<String> replies, RuntimeException ex) {
 
-		if (replies.size() > 0 || ex instanceof PartialSuccessException) {
+		if (!replies.isEmpty() || ex instanceof PartialSuccessException) {
 			return new PartialSuccessException(requestMessage,
 					"Partially successful 'mput' operation" +
 							(subDirectory == null ? "" : (" on " + subDirectory)), ex, replies, filteredFiles);
@@ -1124,7 +1124,7 @@ protected File get(Message<?> message, Session<F> session, String remoteDir, //
 				session.read(remoteFilePath, outputStream);
 			}
 			catch (Exception ex) {
-				/* Some operation systems acquire exclusive file-lock during file processing
+				/* Some operational systems acquire exclusive file-lock during file processing
 				   and the file can't be deleted without closing streams before.
 				*/
 				outputStream.close();
@@ -1223,17 +1223,17 @@ private List<File> mGetWithoutRecursion(Message<?> message, Session<F> session,
 	private RuntimeException processMgetException(Message<?> message, String remoteDirectory, List<File> files,
 			List<AbstractFileInfo<F>> remoteFiles, Exception ex) {
 
-		if (files.size() > 0) {
+		if (!files.isEmpty()) {
 			return new PartialSuccessException(message,
 					"Partially successful recursive 'mget' operation on "
 							+ (remoteDirectory != null ? remoteDirectory : "Client Working Directory"),
 					ex, files, remoteFiles);
 		}
-		else if (ex instanceof MessagingException) {
-			return (MessagingException) ex;
+		else if (ex instanceof MessagingException messagingException) {
+			return messagingException;
 		}
-		else if (ex instanceof IOException) {
-			throw new UncheckedIOException((IOException) ex);
+		else if (ex instanceof IOException ioException) {
+			throw new UncheckedIOException(ioException);
 		}
 		else {
 			return new MessagingException("Failed to process MGET", ex);
@@ -1265,7 +1265,7 @@ private List<AbstractFileInfo<F>> lsRemoteFilesForMget(Message<?> message, Sessi
 
 		@SuppressWarnings("unchecked")
 		List<AbstractFileInfo<F>> remoteFiles = (List<AbstractFileInfo<F>>) ls(message, session, remotePath);
-		if (remoteFiles.size() == 0 && this.options.contains(Option.EXCEPTION_WHEN_EMPTY)) {
+		if (remoteFiles.isEmpty() && this.options.contains(Option.EXCEPTION_WHEN_EMPTY)) {
 			throw new MessagingException("No files found at "
 					+ (remoteDirectory != null ? remoteDirectory : "Client Working Directory")
 					+ " with pattern " + remoteFilename);
@@ -1291,7 +1291,7 @@ private File getRemoteFileForMget(Message<?> message, Session<F> session, String
 
 	private String getRemoteDirectory(String remoteFilePath, String remoteFilename) {
 		String remoteDir = remoteFilePath.substring(0, remoteFilePath.lastIndexOf(remoteFilename));
-		if (remoteDir.length() == 0) {
+		if (remoteDir.isEmpty()) {
 			return null;
 		}
 		return remoteDir;

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2022 the original author or authors.
+ * Copyright 2013-2023 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.
@@ -303,8 +303,8 @@ public void testInt3172LocalDirectoryExpressionMGETRecursive() throws IOExceptio
 		ByteArrayOutputStream localContents = new ByteArrayOutputStream();
 		FileUtils.copyFile(secondRemote, remoteContents);
 		FileUtils.copyFile(secondTarget, localContents);
-		String localAsString = new String(localContents.toByteArray());
-		assertThat(localAsString).isEqualTo(new String(remoteContents.toByteArray()));
+		String localAsString = localContents.toString();
+		assertThat(localAsString).isEqualTo(remoteContents.toString());
 		long oldLastModified = secondRemote.lastModified();
 		FileUtils.copyInputStreamToFile(new ByteArrayInputStream("junk".getBytes()), secondRemote);
 		long newLastModified = secondRemote.lastModified();
@@ -313,13 +313,13 @@ public void testInt3172LocalDirectoryExpressionMGETRecursive() throws IOExceptio
 		this.output.receive(0);
 		localContents = new ByteArrayOutputStream();
 		FileUtils.copyFile(secondTarget, localContents);
-		assertThat(new String(localContents.toByteArray())).isEqualTo(localAsString);
+		assertThat(localContents.toString()).isEqualTo(localAsString);
 		secondRemote.setLastModified(newLastModified);
 		this.inboundMGetRecursive.send(new GenericMessage<Object>("*"));
 		this.output.receive(0);
 		localContents = new ByteArrayOutputStream();
 		FileUtils.copyFile(secondTarget, localContents);
-		assertThat(new String(localContents.toByteArray())).isEqualTo("junk");
+		assertThat(localContents.toString()).isEqualTo("junk");
 		// restore the remote file contents
 		FileUtils.copyInputStreamToFile(new ByteArrayInputStream(localAsString.getBytes()), secondRemote);
 	}
@@ -364,12 +364,12 @@ public void testInt3100RawGET() throws Exception {
 		ByteArrayOutputStream baos = new ByteArrayOutputStream();
 		FileCopyUtils.copy(session.readRaw("ftpSource/ ftpSource1.txt"), baos);
 		assertThat(session.finalizeRaw()).isTrue();
-		assertThat(new String(baos.toByteArray())).isEqualTo("source1");
+		assertThat(baos.toString()).isEqualTo("source1");
 
 		baos = new ByteArrayOutputStream();
 		FileCopyUtils.copy(session.readRaw("ftpSource/ftpSource2.txt"), baos);
 		assertThat(session.finalizeRaw()).isTrue();
-		assertThat(new String(baos.toByteArray())).isEqualTo("source2");
+		assertThat(baos.toString()).isEqualTo("source2");
 
 		session.close();
 	}
@@ -383,12 +383,12 @@ public void testRawGETWithTemplate() {
 		final ByteArrayOutputStream baos1 = new ByteArrayOutputStream();
 		assertThat(template.get(new GenericMessage<>("ftpSource/ ftpSource1.txt"),
 				stream -> FileCopyUtils.copy(stream, baos1))).isTrue();
-		assertThat(new String(baos1.toByteArray())).isEqualTo("source1");
+		assertThat(baos1.toString()).isEqualTo("source1");
 
 		final ByteArrayOutputStream baos2 = new ByteArrayOutputStream();
 		assertThat(template.get(new GenericMessage<>("ftpSource/ftpSource2.txt"),
 				stream -> FileCopyUtils.copy(stream, baos2))).isTrue();
-		assertThat(new String(baos2.toByteArray())).isEqualTo("source2");
+		assertThat(baos2.toString()).isEqualTo("source2");
 	}
 
 	@Test
@@ -817,7 +817,7 @@ public FtpRemoteFileTemplate template(SessionFactory<FTPFile> sf) {
 		@EventListener
 		public void handleEvent(ApacheMinaFtpEvent event) {
 			if (this.latch != null) {
-				if (this.events.size() > 0 || event instanceof SessionOpenedEvent) {
+				if (!this.events.isEmpty() || event instanceof SessionOpenedEvent) {
 					if (event instanceof SessionOpenedEvent) {
 						this.clientAddress = event.getSession().getClientAddress();
 						this.events.add(event);