FileUploadDownloadPoc

FileUploadDownloadPoc is a Spring Boot application that demonstrates storing and retrieving files using an H2 Database. This is a Proof of Concept (PoC) and is not intended for production use.

Features

• File Upload: Upload files (images, PDFs, Word documents) directly to the H2 database.
• File Retrieval: Retrieve files using a file ID.
• Spring Boot & H2 Integration: Uses an in-memory H2 database for temporary storage.

Why Storing Files in a Database is NOT Recommended

Storing files (binary data) directly in a relational database is not a best practice, especially for high-traffic applications. Here’s why:

• Performance Issues: Databases are optimized for structured data, not large binary objects.
• Increased DB Load: Large files increase database size, slowing down queries and backups.
• Scaling Issues: Harder to distribute files across multiple servers efficiently.

When is it Acceptable?

• Only recommended for low-traffic applications or small-scale proof of concepts.

Best Practices for File Storage

• Store files in a server’s file system and save the file path in the database.
• Use cloud storage buckets (Recommended for scalability and reliability), e.g., AWS S3, Google Cloud Storage, or Azure Blob Storage.

API Endpoints

File Operations

Method	Endpoint	Description
POST	/upload	Upload a file
GET	/download/{id}	Retrieve a file by ID

Technologies Used

• Spring Boot
• H2 Database (In-Memory for PoC)
• Spring Data JPA

Changing Content-Disposition: inline vs. attachment

When serving a file in a Spring Boot application, you can control how the browser handles it using the Content-Disposition header.

1️⃣ Setting Content-Disposition in Spring Boot

You can set Content-Disposition

@GetMapping("/download/{id}")
public ResponseEntity<byte[]> downloadFile(@PathVariable Long id){
                                       
    FileEntity file = fileService.getFileById(id);

    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.parseMediaType(file.getFileType()));
    headers.setContentDisposition(ContentDisposition.builder("inline")
            .filename(file.getFileName())
            .build());

    return ResponseEntity.ok()
            .headers(headers)
            .body(file.getData());
}

2️⃣ Difference Between inline and attachment

📄 inline (Direct Display in Browser)

Content-Disposition: inline; filename="document.pdf"

• The browser tries to display the file instead of downloading it.
• Works well for images (.jpg, .png), PDFs (.pdf), and text files (.txt).
• Example: If you request a PDF with inline, the browser opens it in the built-in PDF viewer.

📥 attachment (Forces Download)

Content-Disposition: attachment; filename="document.pdf"

• Forces the browser to prompt for download instead of displaying it.
• Works for all file types.
• Example: When clicking a download link, the browser asks, "Do you want to save this file?"

NOTE

when uploading a file in a Spring Boot REST API, you typically use @RequestParam instead of @RequestBody because:

Serialization Limitation: Files (binary data) cannot be directly serialized into JSON or other text-based formats used in @RequestBody.

Multipart Form Data: File uploads require multipart/form-data encoding, which @RequestParam supports.

Spring Support: Spring provides built-in support for handling file uploads using MultipartFile, which works seamlessly with @RequestParam.

H2-Console

Swagger

POSTMAN