如何从 Spring 的组件中调用配置中的 SFTP 出站网关操作

Question

I have looked here here and am unable to get listFiles to work:

    @Bean
    public SessionFactory<LsEntry> sftpSessionFactory() {
        DefaultSftpSessionFactory factory = new DefaultSftpSessionFactory(true);
        factory.setHost("localhost");
        factory.setPort(port);
        factory.setUser("foo");
        factory.setPassword("foo");
        factory.setAllowUnknownKeys(true);
        factory.setTestSession(true);
        return new CachingSessionFactory<LsEntry>(factory);
    }

    @MessagingGateway
    public interface MyGateway {
         @Gateway(requestChannel = "sftpChannel")
         List<File> listFiles();

    }
    @Bean
    @ServiceActivator(inputChannel = "sftpChannel")
    public MessageHandler handler() {
        return new SftpOutboundGateway(ftpSessionFactory(), "ls", "'my_remote_dir/'");
    }

where in my @Component class I have this:

    @Autowired
    MyGateway gateway;

    public void list(){
        List<File> files = gateway.listFiles();
    }

when I run this, I get an error receive is not supported, because no pollable reply channel has been configured

I assume this is an issue with my knowledge/understanding of integration channels. Perhaps I am missing a bean, but my main goal here is to do replace my current use of the inboundchannel adapter to request files ad hoc instead of continuously polling the fileserver

Answer 1

Yes, the story mentioned in the Spring Integration Gateway with no arguments is definitely related to your problem.

You are missing the fact that List<File> listFiles() contract comes without arguments, so it is not clear for the framework what to use for sending to that sftpChannel . Therefore it try to call receive . But since your sftpChannel is not PollableChannel , you got that error. Anyway that is a different story and not what you want to get as a reply from sending a message to the sftpChannel as you try to do with that gateway contract.

You just need to be more explicit and say what to use as a payload for that no-arg gateway contract.

See more info in docs: https://docs.spring.io/spring-integration/docs/current/reference/html/messaging-endpoints.html#gateway-calling-no-argument-methods . The @Payload is an answer for you. Or you can specify a payloadExpression on that @Gateway annotation or a defaultPayloadExpression on the @MessagingGateway .

Answer 2

Maybe it is too late, but you also could change your no-arg gateway contract to a one-arg contract having nothing to annotate additionally.

@MessagingGateway
public interface MyGateway {
     @Gateway(requestChannel = "sftpChannel")
     List<File> listFiles(String remoteDir);

}

@Bean
@ServiceActivator(inputChannel = "sftpChannel")
public MessageHandler handler() {
    return new SftpOutboundGateway(ftpSessionFactory(), Command.LS, "payload");
}

In your @Component class then you will have:

@Autowired
MyGateway gateway;

public void list(){
    List<File> files = gateway.listFiles("'my_remote_dir/'");
}