GH-9821: SFTP: Use STAT command to follow symlinks

Fixes: #9821
Issue link: #9821

Previously, Spring Integration used JSch library for SFTP protocol,
and that one was able to follow symlinks.
Currently, the `SftpSession` uses `LSTAT` command which does not follow symlinks

* Fix `SftpSession` to call `sftpClient.stat()` instead of `lstat()`
to mitigate migration pain from JSch

**Auto-cherry-pick to `6.4.x` & `6.3.x`**

Author: artembilan

spring-integration-sftp/src/main/java/org/springframework/integration/sftp/session/SftpSession.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -101,7 +101,7 @@ public Stream<SftpClient.DirEntry> doList(String path) throws IOException {
 		boolean isPattern = remoteFile != null && remoteFile.contains("*");
 
 		if (!isPattern && remoteFile != null) {
-			SftpClient.Attributes attributes = this.sftpClient.lstat(path);
+			SftpClient.Attributes attributes = this.sftpClient.stat(path);
 			if (!attributes.isDirectory()) {
 				return Stream.of(new SftpClient.DirEntry(remoteFile, path, attributes));
 			}
@@ -201,7 +201,7 @@ public boolean rmdir(String remoteDirectory) throws IOException {
 	@Override
 	public boolean exists(String path) {
 		try {
-			this.sftpClient.lstat(normalizePath(path));
+			this.sftpClient.stat(normalizePath(path));
 			return true;
 		}
 		catch (SftpException ex) {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -279,15 +279,15 @@ public void testExists() throws IOException {
 
 		willReturn(new SftpClient.Attributes())
 				.given(sftpClient)
-				.lstat("/exist");
+				.stat("/exist");
 
 		willThrow(new SftpException(SftpConstants.SSH_FX_NO_SUCH_FILE, "notExist"))
 				.given(sftpClient)
-				.lstat("/notExist");
+				.stat("/notExist");
 
 		willThrow(new SshException(SshConstants.SSH_OPEN_CONNECT_FAILED, "Connection lost."))
 				.given(sftpClient)
-				.lstat(and(not(eq("/exist")), not(eq("/notExist"))));
+				.stat(and(not(eq("/exist")), not(eq("/notExist"))));
 
 		SftpSession sftpSession = new SftpSession(sftpClient);
 

spring-integration-sftp/src/test/java/org/springframework/integration/sftp/session/SftpRemoteFileTemplateTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2024 the original author or authors.
+ * Copyright 2014-2025 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.
@@ -86,7 +86,7 @@ public void testINT3412AppendStatRmdir() {
 		assertThat(template.exists("foo/foobar.txt")).isTrue();
 		template.executeWithClient((ClientCallbackWithoutResult<SftpClient>) client -> {
 			try {
-				SftpClient.Attributes file = client.lstat("foo/foobar.txt");
+				SftpClient.Attributes file = client.stat("foo/foobar.txt");
 				assertThat(file.getSize()).isEqualTo(6);
 			}
 			catch (IOException e) {