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intermediate Phase · Files and Storage

Multipart Upload

Handle multipart form data for file uploads.

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Multipart Upload

Spring Boot Multipart

@PostMapping("/upload")
public ResponseEntity<?> upload(
        @RequestParam("file") MultipartFile file) {
    if (file.isEmpty()) return ResponseEntity.badRequest().build();
    if (file.getSize() > 10_000_000) return ResponseEntity.status(413).build();

    String filename = file.getOriginalFilename();
    byte[] bytes = file.getBytes();
    // Store...
    return ResponseEntity.ok("Uploaded: " + filename);
}

Configuration

spring.servlet.multipart.max-file-size=10MB
spring.servlet.multipart.max-request-size=10MB

Best Practices

Key Principles

  1. Follow SOLID principles
  2. Write clean, readable code
  3. Test thoroughly
  4. Document decisions
  5. Monitor in production

Implementation

  • Start simple, refactor as needed
  • Use established patterns
  • Consider trade-offs
  • Review with peers

Continuous Improvement

  • Learn from incidents
  • Update documentation
  • Share knowledge
  • Mentor others

Key Points

  • Understanding Multipart Upload is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Practice Problems

0 / 3 solved
Implement Multipart Upload

Design and implement a solution for Multipart Upload in a backend system. Consider scalability, error handling, and production readiness.

Solution 
// Multipart Upload implementation
// Key aspects: validation, error handling, logging, testing

public class MultipartUpload {
    // Production-ready implementation
}
Multipart Upload Edge Cases

Identify and handle edge cases for Multipart Upload. What happens under high load, with invalid input, or during failures?

Solution 
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotency
Multipart Upload Testing Strategy

Write a testing strategy for Multipart Upload. Include unit tests, integration tests, and performance tests.

Solution 
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injection

Quiz

1. MultipartFile represents?

Question 1 options

2. Max file size configured via?

Question 2 options

3. What is a common mistake when implementing Multipart Upload?

Question 3 options

Flashcards

Question

MultipartFile?

Click to reveal answer

Answer

Spring representation of uploaded file

Question

Max file size config?

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Answer

spring.servlet.multipart.max-file-size

Question

Multipart Upload best practices

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Answer

Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.

Revision Notes

Key Takeaways

  • 1. MultipartFile handles uploaded files
  • 2. Configure max-file-size in properties
  • 3. Always validate: empty, size, type
  • 4. Store in object storage, not filesystem

Interview Tips

  • • Handle file uploads
  • • Validate file constraints

Cheat Sheet

Multipart Upload

  • MultipartFile for handling
  • Config: spring.servlet.multipart.max-file-size
  • Validate: empty, size, type
  • Store: S3/object storage