Spring Integration: How to dynamically create subdir on sftp using IntegrationFlow - spring-integration

Question

I have a use case for transfering files to sftp under certain subdirs that are created dynamically.
I got this working using custom SftpMessageHandler method and a Gateway. But the issue with this approach was, it was not deleting local temp files after successful upload.
To solve that, now I am using IntegrationFlow along with expression Advice (as below), this does remove local files, but I don't know how to create remote subDirs dynamically. I read about remote directory expression, but not sure how to use/implement it.
Any one resolved this issue? Any help is appreciated!
#Bean
public IntegrationFlow sftpOutboundFlow() {
return IntegrationFlows.from("toSftpChannel")
.handle(Sftp.outboundAdapter(this.sftpSessionFactory())
.remoteFileSeparator("/")
.useTemporaryFileName(false)
.remoteDirectory("/temp"), c -> c.advice(expressionAdvice(c)))
.get();
}
#Bean
public Advice expressionAdvice(GenericEndpointSpec<FileTransferringMessageHandler<ChannelSftp.LsEntry>> c) {
ExpressionEvaluatingRequestHandlerAdvice advice = new ExpressionEvaluatingRequestHandlerAdvice();
advice.setOnSuccessExpressionString("payload.delete()");
advice.setOnFailureExpressionString("payload + ' failed to upload'");
advice.setTrapException(true);
return advice;
}
#MessagingGateway
public interface UploadGateway {
#Gateway(requestChannel = "toSftpChannel")
void upload(File file);
}

Answer 1

The Sftp.outboundAdapter() has these options for the remote directory:
/**
* Specify a remote directory path.
* #param remoteDirectory the remote directory path.
* #return the current Spec
*/
public S remoteDirectory(String remoteDirectory) {
}
/**
* Specify a remote directory path SpEL expression.
* #param remoteDirectoryExpression the remote directory expression
* #return the current Spec
*/
public S remoteDirectoryExpression(String remoteDirectoryExpression) {
}
/**
* Specify a remote directory path {#link Function}.
* #param remoteDirectoryFunction the remote directory {#link Function}
* #param <P> the expected payload type.
* #return the current Spec
*/
public <P> S remoteDirectory(Function<Message<P>, String> remoteDirectoryFunction) {
}
So, if the story is about a dynamic sub-directory, you can choose a remoteDirectoryExpression or remoteDirectory(Function) and calculate a target path against message or some bean in the application context.
For example:
.remoteDirectoryExpression("'rootDir/' + headers.subDir")
Also bear in mind that for not existing directories you need to configure an .autoCreateDirectory(true), too.