能否将Spring Integration的SFTP入站适配器对接S3存储而非本地文件系统？

Great question! Let's break this down clearly:

First, a straight answer: Spring Integration's SFTP Inbound Channel Adapter cannot directly connect to an S3 bucket out of the box. The SFTP adapter is purpose-built to interact with servers using the SFTP protocol, while S3 uses its own REST-based API (or S3-compatible protocols) — they're fundamentally different systems.

But don't worry, there are two solid approaches to achieve your goal of integrating S3 with Spring Integration's file-processing workflow, depending on your needs:

Approach 1: Replace the SFTP Adapter with Spring Integration's S3 Inbound Adapter #

If you don't strictly need to use the SFTP protocol (i.e., your source system can work directly with S3), this is the most efficient and straightforward solution. Spring Integration has a dedicated AWS S3 module that provides an inbound adapter for polling S3 buckets.

Step-by-Step Configuration #

1. Add the required dependency (Maven example):

   <dependency>
       <groupId>org.springframework.integration</groupId>
       <artifactId>spring-integration-aws</artifactId>
       <version>your-spring-integration-version</version>
   </dependency>
   

2. Configure the S3 inbound flow:

   @Configuration
   @EnableIntegration
   public class S3InboundIntegrationConfig {
   
       @Value("${aws.s3.target-bucket}")
       private String targetS3Bucket;
   
       // Inject your AmazonS3 client (configured with AWS credentials/region)
       @Autowired
       private AmazonS3 amazonS3Client;
   
       @Bean
       public S3SessionFactory s3SessionFactory() {
           return new S3SessionFactory(this.amazonS3Client);
       }
   
       @Bean
       @InboundChannelAdapter(channel = "s3FileInputChannel", poller = @Poller(fixedDelay = "15000"))
       public MessageSource<File> s3InboundAdapter() {
           // Synchronizer handles fetching files from S3 to local staging
           S3InboundFileSynchronizingMessageSource messageSource =
                   new S3InboundFileSynchronizingMessageSource(s3FileSynchronizer());
           // Local directory to stage downloaded S3 objects (can be temp dir)
           messageSource.setLocalDirectory(new File("./s3-local-staging"));
           messageSource.setAutoCreateLocalDirectory(true);
           return messageSource;
       }
   
       @Bean
       public S3InboundFileSynchronizer s3FileSynchronizer() {
           S3InboundFileSynchronizer synchronizer = new S3InboundFileSynchronizer(s3SessionFactory());
           synchronizer.setRemoteDirectory(targetS3Bucket);
           // Optional: Filter files (e.g., only process .json files)
           synchronizer.setFilter(new S3SimplePatternFileListFilter("*.json"));
           return synchronizer;
       }
   
       @Bean
       public MessageChannel s3FileInputChannel() {
           return new DirectChannel();
       }
   
       @Bean
       @ServiceActivator(inputChannel = "s3FileInputChannel")
       public MessageHandler s3FileProcessor() {
           return message -> {
               File stagedFile = (File) message.getPayload();
               // Add your business logic here (process the file)
               System.out.printf("Processing S3 file: %s%n", stagedFile.getName());
           };
       }
   }
   

This setup polls your S3 bucket at regular intervals, downloads objects to a local staging directory, and sends them to your processing handler.

Approach 2: Use an SFTP-to-S3 Gateway as an Intermediate Layer #

If you must retain the SFTP protocol (e.g., your upstream system can only send files via SFTP), you can use a gateway service that bridges SFTP to S3. AWS Transfer Family is a managed service that does exactly this: it provides an SFTP endpoint that maps directly to an S3 bucket.

Step-by-Step Setup #

1. Deploy an AWS Transfer Family SFTP server:

   • In the AWS Console, create a Transfer Family server with SFTP protocol.
   • Configure its storage to point to your target S3 bucket (map SFTP directories to S3 prefixes as needed).
   • Set up user credentials (SSH keys or passwords) for your Spring Integration adapter to use.

2. Configure the Spring Integration SFTP Adapter to connect to this gateway:
   This is identical to configuring the SFTP adapter for a traditional SFTP server — the only difference is the host/credentials point to your Transfer Family endpoint.

   @Configuration
   @EnableIntegration
   public class SftpToS3IntegrationConfig {
   
       @Value("${transfer-family.sftp.host}")
       private String sftpHost;
   
       @Value("${transfer-family.sftp.port:22}")
       private int sftpPort;
   
       @Value("${transfer-family.sftp.username}")
       private String sftpUsername;
   
       @Value("${transfer-family.sftp.private-key-path}")
       private String sftpPrivateKeyPath;
   
       @Bean
       public SessionFactory<ChannelSftp.LsEntry> sftpSessionFactory() {
           DefaultSftpSessionFactory factory = new DefaultSftpSessionFactory(true);
           factory.setHost(sftpHost);
           factory.setPort(sftpPort);
           factory.setUser(sftpUsername);
           factory.setPrivateKey(new FileSystemResource(sftpPrivateKeyPath));
           factory.setAllowUnknownKeys(true); // For testing; use known_hosts in production
           return new CachingSessionFactory<>(factory);
       }
   
       @Bean
       @InboundChannelAdapter(channel = "sftpFileInputChannel", poller = @Poller(fixedDelay = "10000"))
       public MessageSource<File> sftpInboundAdapter() {
           SftpInboundFileSynchronizingMessageSource messageSource =
                   new SftpInboundFileSynchronizingMessageSource(sftpFileSynchronizer());
           messageSource.setLocalDirectory(new File("./sftp-local-staging"));
           messageSource.setAutoCreateLocalDirectory(true);
           return messageSource;
       }
   
       @Bean
       public SftpInboundFileSynchronizer sftpFileSynchronizer() {
           SftpInboundFileSynchronizer synchronizer = new SftpInboundFileSynchronizer(sftpSessionFactory());
           synchronizer.setRemoteDirectory("/"); // Maps to S3 bucket root
           synchronizer.setFilter(new SftpSimplePatternFileListFilter("*.csv"));
           return synchronizer;
       }
   
       // Channel and processor bean definitions same as Approach 1...
   }
   

When files are uploaded to the Transfer Family SFTP endpoint, they're automatically stored in S3. Your Spring Integration SFTP adapter will poll this endpoint and process files as if they were on a traditional SFTP server.

Key Takeaway #

• Skip the SFTP adapter entirely and use the S3 adapter if you don't need the SFTP protocol — it's more efficient and avoids unnecessary layers.
• Use an SFTP-to-S3 gateway like AWS Transfer Family if you must maintain SFTP compatibility.

内容的提问来源于stack exchange，提问作者Rori Stumpf