Spring Integration：SFTP顺序上传文件后如何获取返回值

Hey there! Let's work through your SFTP sequential upload issue together. From what you shared, you're building a Spring Boot feature that needs to upload a PDF first, then its metadata text file only after the PDF upload succeeds. But when you call your Gateway's upload method, you're not getting the expected confirmation message (The SFTP transfer complete for file:...)—instead, you're getting some other upload-related content.

Here are actionable steps to troubleshoot and fix this:

1. Double-check your Gateway's return logic #

First, verify that your Gateway's upload method is explicitly returning the custom confirmation string only after both uploads succeed. It’s easy to accidentally return the raw response from your SFTP client (like a boolean success flag or remote file path) instead of your intended message.

For example, if you’re using Spring Integration’s SFTP tools, make sure your method wraps the upload calls and constructs the message explicitly:

public String upload(File pdfFile, File metaFile) {
    // Step 1: Upload PDF and confirm success
    boolean pdfUploaded = sftpService.uploadFile(pdfFile, "/remote/pdfs/");
    if (!pdfUploaded) {
        throw new UploadFailedException("PDF upload failed");
    }

    // Step 2: Upload metadata only after PDF succeeds
    boolean metaUploaded = sftpService.uploadFile(metaFile, "/remote/meta/");
    if (!metaUploaded) {
        throw new UploadFailedException("Metadata upload failed");
    }

    // Return your custom confirmation message here
    return "The SFTP transfer complete for file: " + pdfFile.getName();
}

2. Ensure strict sequential execution #

Make sure your two upload steps run synchronously and in order. If you’re using @Async annotations or an asynchronous SFTP client, the Gateway method might return before the metadata upload finishes, leading to an unexpected result.

Add log statements between steps to confirm execution order:

log.info("Successfully uploaded PDF: {}", pdfFile.getName());
// Upload metadata here
log.info("Successfully uploaded metadata for: {}", pdfFile.getName());

3. Validate upload success properly #

Don’t just rely on the absence of exceptions to confirm upload success. Some SFTP clients might not throw errors for partial uploads or permission issues. Add extra checks to verify the files exist on the remote server:

// After PDF upload
if (!sftpRemoteFileTemplate.exists("/remote/pdfs/" + pdfFile.getName())) {
    throw new UploadFailedException("PDF not found on remote server after upload");
}

4. Debug the return value flow #

Set a breakpoint in your Gateway’s upload method to inspect what value it’s actually returning. Is it pulling a result from the SFTP client instead of your custom string? If so, adjust the method to overwrite that result with your intended confirmation message.

5. Check for hidden exception handling #

If your app has a global exception handler, it might be catching upload errors and returning a generic response that you’re mistaking for a normal result. Check your application logs for any uncaught exceptions that could be interrupting the flow before your confirmation message is returned.

内容的提问来源于stack exchange，提问作者Rok Purkeljc