Have you used AWS S3?

AWS S3 Document Upload & Download — Steps

Step 1: AWS S3 Setup

• Create S3 bucket: bucket-name
• Region: us-east-1
• Block public access ✅
• Create IAM user with AmazonS3FullAccess → get Access & Secret Key

Step 2: Add Dependencies (Spring Boot)

• E.g., software.amazon.awssdk:s3

Step 3: application.yml

aws:

s3:

bucket-name: your-bucket

region: us-east-1

access-key: YOUR_ACCESS_KEY

secret-key: YOUR_SECRET_KEY

Step 4: S3 Configuration Class

• Create S3Client bean with credentials

Step 5: S3 Service (Core Logic)

• uploadFile(MultipartFile file) → uploads to S3
• downloadFile(String fileName) → downloads from S3

Step 6: REST Controller

@PostMapping(“/upload”)

public ResponseEntity<String> upload(@RequestParam(“file”) MultipartFile file)

@GetMapping(“/download/{fileName}”)

public ResponseEntity<byte[]> download(@PathVariable String fileName)

Step 7: Store in Database (File URL)

• After uploading to S3, save the file key or URL in DB

Step 8: React Example

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await fetch(“http://localhost:8080/api/files/upload", {

method: “POST”,

body: formData,

});

Normal Flow (Backend uploads file to S3)

• Backend uploads file to S3 → S3 returns file key or URL
• You store file name / key / S3 URL in DB

Pre-Signed URL Flow (Frontend uploads directly to S3)

• Backend generates pre-signed URL → frontend uploads file directly
• After upload, you store file name or final S3 URL in DB