sftputility

A simple java utility which provides a wrapper over JSCH library to perform some useful sftp operations.

Note:

• Uses JSCH version 0.1.54
• Uses commons-logging version 1.2
• Uses lombok with builder pattern

Requirements

• Java 8
• Lombok plugin installed as per your IDE (Check Install section of lombok)

Usage with spring boot

Read the mandatory properties into a bean:

@Getter
@Setter
@ToString
@Configuration
public class SftpParams {
	
	@Value("${sftp.host}")
	private String host;
	
	@Value("${sftp.username}")
	private String userName;
	
	@Value("${sftp.password}")
	private String password;
	
	@Value("${sftp.port}")
	private int port;
	
	@Value("${sftp.homepath}")
	private String homePath;

}

Initialize the SftpService bean using spring's @Configuration :

@Configuration
public class SftpConfigurator {

	@Autowired
	private SftpParams sftpParams;

	@Bean
	public SftpService getSftpService() throws SftpConfigException {
		SftpConfig sftpConfig = SftpConfig.builder().host(sftpParams.getHost()).userName(sftpParams.getUserName())
				.password(sftpParams.getPassword()).port(22).homePath(sftpParams.getHomePath()).build();
		SftpService sftpService = new SftpServiceImpl();
		sftpService.initialize(sftpConfig);
		return sftpService;
	}

}

Now you can use the SftpService interface methods to perform sftp operations.

Currently, the library supports the following functions on remote server:

1. Create a single directory
2. Create multiple directories like Java's Files.createDirectories(Path) method if the given path contains directories not created till terminal directory.
3. cd into home directory(explained in the next section).
4. Upload a single file using File object or local file path.
5. Upload a list of Files (List<String> fileList but not List<File> fileList).
6. Upload multiple folderwise files i.e.
   • Folder A - abc.txt, bcd.txt
   • Folder B - def.txt, xyz.txt
7. Download all files from specified remote folder to given local path.
8. Delete a single file with given absolute remote path.
9. Delete multiple files with given list of absolute remote file path.
10. Move multiple files with their absolute file path to a given remote path.

Points to keep in mind while using this utility:

• homepath property should follow sftp protocol file separator i.e. / and should not end in /
  i.e. /home/user
• If the destRelativePath variable is passed as null, then it will default to homepath in all the functions.
• After being connected to remote by sftp, each operation will be performed relative to the homepath. Hence, you should pass relative paths to functions with destRelativePath arguments.
• All remote paths should always contain sftp file separator i.e. / since sftp protocol is independent of remote operating system.
• Local file paths can use their operating system dependent file separator i.e. \ for Windows and / for Linux/Mac based operating system since internally Java's NIO Path has been used to handle local file paths which makes this library perform operations to and from Windows/Linux Operating systems.

Improvements / Suggestions

Due to time constraints, I could not avoid the duplication of creating session and channel code across all functions. This might be refactored in one way such as:
Call a common method say doSftpOperation(OperationType, RequiredArguments) which internally
creates session and channel once, then call the specific method based on operation type with the required arguments along with the ChannelSftp. But this will create either lot's of if/switch-case statements which will create a lot of mess if the functions performed by SftpService increase overtime in future. Hence, any suggestions to improve/tackle this challenge are welcome.

Currently, in some functions, Session and Channel are created at most twice due to the above mentioned logic. If the suggested refactoring is done, then this will be avoided.

The SftpService interface currently throws exceptions which are tied to JSCH library. This can be generalized by throwing some common SftpException from the interface methods. While the implementation should take care of catching internal library specific exceptions and throwing the common SftpException instead to hide underlying library.

Also, I'm a big fan of Java 7's try-with-resource but unfortunately JSCH objects do not implement AutoCloseable interface hence had to try/finally blocks to close resources. While searching for alternatives, I found an awesome library Apache MINA SSHD which supports try-with-resource. I struggled a lot even to find a simple code to connect to remote server using this library. But this might be mostly due to my lacking experience or time. Another implementation or library using Apache Mina would be welcome!

Feel free to tinker around this code and improve this further!