文件下载后如何断开 FTP 服务器连接？

Question

使用 Spring FTP 集成和注释配置，我从 FTP 服务器下载了文件。下载后，我们的应用程序仍然触发连接服务器并查找任何新添加的文件，如果添加了任何文件，它将从服务器下载。但是我不需要在第一次连接或第一次下载后保持 FTP 服务器会话处于活动状态并断开服务器。

代码：

public class FtpServices {

    @Bean(name="ftpSessionFactory")
    public DefaultFtpSessionFactory ftpSessionFactory() {
        System.out.println("session");

        DefaultFtpSessionFactory sf = new DefaultFtpSessionFactory();
        sf.setHost("localhost");
        sf.setPort(21);
        sf.setUsername("user");
        sf.setPassword("password");

        return sf;
    }

    @Bean
    public FtpInboundFileSynchronizer ftpInboundFileSynchronizer() {
        System.out.println("2");
        FtpInboundFileSynchronizer fileSynchronizer = new FtpInboundFileSynchronizer(ftpSessionFactory());
        fileSynchronizer.setDeleteRemoteFiles(false);
        fileSynchronizer.afterPropertiesSet();
        fileSynchronizer.setRemoteDirectory("/test/");
       // fileSynchronizer.setFilter(new FtpSimplePatternFileListFilter("*.docx"));
        fileSynchronizer.setFilter(filter);
        return fileSynchronizer;
    }

    @Bean()
    @InboundChannelAdapter(value="ftpChannel", poller = @Poller(fixedDelay = "50", maxMessagesPerPoll = "1"))
    public FtpInboundFileSynchronizingMessageSource ftpMessageSource() {
        System.out.println(3);
        FtpInboundFileSynchronizingMessageSource source =
                new FtpInboundFileSynchronizingMessageSource(ftpInboundFileSynchronizer());
        source.setLocalDirectory(new File("D:/Test-downloaded/"));
        //source.stop();
        return source;
    }

    @Bean
    @ServiceActivator(inputChannel = "ftpChannel", requiresReply="false")
    public MessageHandler handler() {
        System.out.println(4);
        MessageHandler handler =  new MessageHandler() {

            @Override
            public void handleMessage(Message<?> message) throws MessagingException {
                System.out.println(message.getPayload()+" @ServiceActivator");
                System.out.println(" Message Header :"+message.getHeaders());
            }
        };
        return handler;
    }

    @Bean(name = PollerMetadata.DEFAULT_POLLER)
    public PollerMetadata defaultPoller() {

        PollerMetadata pollerMetadata = new PollerMetadata();
        pollerMetadata.setTrigger(triggerOnlyOnce());
        return pollerMetadata;
    }

}

我还重写了 AbtractFTPSessionFactory.java 来测试 FTP 服务器的连接和断开过程。

protected void postProcessClientAfterConnect(T t) throws IOException {
    System.out.println("After connect");
}

protected void postProcessClientBeforeConnect(T client) throws IOException {
    System.out.println("Before connect");
}

控制台：

    INFO : org.springframework.context.support.DefaultLifecycleProcessor - Starting beans in phase -2147483648
    INFO : org.springframework.context.support.DefaultLifecycleProcessor - Starting beans in phase 0
    Before connect
    After connect
    D:\Test-downloaded\demo 1.txt @ServiceActivator
     Message Header :{id=e4a1fd7f-0bbf-9692-f70f-b0ac68b4dec4, timestamp=1477317086272}
    D:\Test-downloaded\demo.txt @ServiceActivator
     Message Header :{id=9115ee92-12b4-bf1f-d592-9c13bf7a27fa, timestamp=1477317086324}
    Before connect
    After connect
    Before connect
    After connect
    Before connect
    After connect
    Before connect
    After connect
    Before connect
    After connect
    Before connect
    After connect

谢谢。

Answer 1

这确实是任何@InboundChannelAdapter 的目的：定期轮询目标系统以获取新数据。

我们有时建议OnlyOnceTrigger：

public class OnlyOnceTrigger implements Trigger {

    private final AtomicBoolean done = new AtomicBoolean();

    @Override
    public Date nextExecutionTime(TriggerContext triggerContext) {
           return !this.done.getAndSet(true) ? new Date() : null;
    }

}

但这可能不适用于您的情况，因为源 FTP 目录中可能还没有所需的文件。

因此，我们必须轮询，直到您收到所需的文件并在满足该条件时.stop() 适配器。

为此，您可以使用任何下游逻辑来确定状态或考虑实现AbstractMessageSourceAdvice 以注入@Poller 的PollerMetadata：http://docs.spring.io/spring-integration/reference/html/messaging-channels-section.html#conditional-pollers