Spring SFTP Outbound Adapter - determining when files have been sent

Question

I have a Spring SFTP output adapter that I start via "adapter.start()" in my main program. Once started, the adapter transfers and uploads all the files in the specified directory as expected. But I want to stop the adapter after all the files have been transferred. How do I detect if all the files have been transferred so I can issue an adapter.stop()?

@Bean
public IntegrationFlow sftpOutboundFlow() {
    return IntegrationFlows.from(Files.inboundAdapter(new File(sftpOutboundDirectory))
                    .filterExpression("name.endsWith('.pdf') OR name.endsWith('.PDF')")
                    .preventDuplicates(true),
            e -> e.id("sftpOutboundAdapter")
                    .autoStartup(false)
                    .poller(Pollers.trigger(new FireOnceTrigger())
                            .maxMessagesPerPoll(-1)))
            .log(LoggingHandler.Level.INFO, "sftp.outbound", m -> m.getPayload())
            .log(LoggingHandler.Level.INFO, "sftp.outbound", m -> m.getHeaders())
            .handle(Sftp.outboundAdapter(outboundSftpSessionFactory())
                    .useTemporaryFileName(false)
                    .remoteDirectory(sftpRemoteDirectory))
            .get();
}

Answer 1

@Artem Bilan has already given the answer. But here's kind of a concrete implementation of what he said - for those who are a Spring Integration noob like me:

1. Define a service to get the PDF files on demand:

@Service
public class MyFileService {
    public List<File> getPdfFiles(final String srcDir) {
        File[] files = new File(srcDir).listFiles((dir, name) -> name.toLowerCase().endsWith(".pdf"));
        return Arrays.asList(files == null ? new File[]{} : files);
    }
}

2. Define a Gateway to start the SFTP upload flow on demand:

@MessagingGateway
public interface SFtpOutboundGateway {
    @Gateway(requestChannel = "sftpOutboundFlow.input")
    void uploadFiles(List<File> files);
}

3. Define the Integration Flow to upload the files to the SFTP server via Sftp.outboundGateway:

@Configuration
@EnableIntegration
public class FtpFlowIntegrationConfig {
    // could be also bound via @Value 
    private String sftpRemoteDirectory = "/path/to/remote/dir";

    @Bean
    public SessionFactory<ChannelSftp.LsEntry> outboundSftpSessionFactory() {
        DefaultSftpSessionFactory factory = new DefaultSftpSessionFactory(true);
        factory.setHost("localhost");
        factory.setPort(22222);
        factory.setUser("client1");
        factory.setPassword("password123");
        factory.setAllowUnknownKeys(true);
        return new CachingSessionFactory<>(factory);
    }

    @Bean
    public IntegrationFlow sftpOutboundFlow(RemoteFileTemplate<ChannelSftp.LsEntry> remoteFileTemplate) {
        return e -> e
                .log(LoggingHandler.Level.INFO, "sftp.outbound", Message::getPayload)
                .log(LoggingHandler.Level.INFO, "sftp.outbound", Message::getHeaders)
                .handle(
                    Sftp.outboundGateway(remoteFileTemplate, AbstractRemoteFileOutboundGateway.Command.MPUT, "payload")
                );
    }

    @Bean
    public RemoteFileTemplate<ChannelSftp.LsEntry> remoteFileTemplate(SessionFactory<ChannelSftp.LsEntry> outboundSftpSessionFactory) {
        RemoteFileTemplate<ChannelSftp.LsEntry> template = new SftpRemoteFileTemplate(outboundSftpSessionFactory);
        template.setRemoteDirectoryExpression(new LiteralExpression(sftpRemoteDirectory));
        template.setAutoCreateDirectory(true);
        template.afterPropertiesSet();
        template.setUseTemporaryFileName(false);
        return template;
    }
}

Wiring up:

public class SpringApp {
    public static void main(String[] args) {
        final MyFileService fileService = ctx.getBean(MyFileService.class);
        final SFtpOutboundGateway sFtpOutboundGateway = ctx.getBean(SFtpOutboundGateway.class);
        // trigger the sftp upload flow manually - only once
        sFtpOutboundGateway.uploadFiles(fileService.getPdfFiles()); 
    }
}

Import notes:

1.

@Gateway(requestChannel = "sftpOutboundFlow.input") void uploadFiles(List files);

Here the DirectChannel channel sftpOutboundFlow.input will be used to pass message with the payload (= List<File> files) to the receiver. If this channel is not created yet, the Gateway is going to create it implicitly.

2.

@Bean public IntegrationFlow sftpOutboundFlow(RemoteFileTemplate<ChannelSftp.LsEntry> remoteFileTemplate) { ... }

Since IntegrationFlow is a Consumer functional interface, we can simplify the flow a little using the IntegrationFlowDefinition. During the bean registration phase, the IntegrationFlowBeanPostProcessor converts this inline (Lambda) IntegrationFlow to a StandardIntegrationFlow and processes its components. An IntegrationFlow definition using a Lambda populates DirectChannel as an inputChannel of the flow and it is registered in the application context as a bean with the name sftpOutboundFlow.input in the sample above (flow bean name + ".input"). That's why we use that name for the SFtpOutboundGateway gateway.

Ref: https://spring.io/blog/2014/11/25/spring-integration-java-dsl-line-by-line-tutorial

3.

@Bean public RemoteFileTemplate<ChannelSftp.LsEntry> remoteFileTemplate(SessionFactory<ChannelSftp.LsEntry> outboundSftpSessionFactory) {}

see: Remote directory for sftp outbound gateway with DSL

Flowchart: