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intermediate Phase · Spring Boot Fundamentals

Request Parameters

Extract query parameters, path variables, and request bodies.

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Request Parameters

@RequestParam

@GetMapping("/products")
public ResponseEntity<List<Product>> getProducts(
        @RequestParam String category,
        @RequestParam(defaultValue = "0") int page,
        @RequestParam(defaultValue = "20") int size,
        @RequestParam(required = false) BigDecimal minPrice) {
    // category is required
    // page defaults to 0
    // minPrice is optional (can be null)
    return ResponseEntity.ok(productService.filter(category, minPrice, page, size));
}

Parameter Binding

Source Annotation Example URL
Query parameter @RequestParam /products?category=phone
Path variable @PathVariable /products/123
Request body @RequestBody POST body JSON
Header @RequestHeader Authorization: Bearer ...
Cookie @CookieValue session=abc123

Required vs Optional

// Required (default)
@RequestParam String name       // 400 if missing

// Optional with default
@RequestParam(defaultValue = "10") int size

// Optional (nullable)
@RequestParam(required = false) String search

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 Request Parameters 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 Request Parameters

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

Solution 
// Request Parameters implementation
// Key aspects: validation, error handling, logging, testing

public class RequestParameters {
    // Production-ready implementation
}
Request Parameters Edge Cases

Identify and handle edge cases for Request Parameters. 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
Request Parameters Testing Strategy

Write a testing strategy for Request Parameters. 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. What happens when a required @RequestParam is missing?

Question 1 options

2. How do you make a @RequestParam optional?

Question 2 options

3. What is a common mistake when implementing Request Parameters?

Question 3 options

Flashcards

Question

What happens with missing required @RequestParam?

Click to reveal answer

Answer

Returns 400 Bad Request

Question

How to make @RequestParam optional?

Click to reveal answer

Answer

required = false or defaultValue

Question

Request Parameters best practices

Click to reveal answer

Answer

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

Revision Notes

Key Takeaways

  • 1. @RequestParam extracts query parameters
  • 2. Required by default, use required=false for optional
  • 3. defaultValue provides fallback values
  • 4. @RequestHeader, @CookieValue for headers/cookies

Interview Tips

  • • Know parameter binding annotations
  • • Handle required vs optional parameters

Cheat Sheet

Request Parameters

  • @RequestParam: Query params (?key=value)
  • @PathVariable: Path segments (/products/{id})
  • @RequestBody: JSON body
  • @RequestHeader: HTTP headers
  • @CookieValue: Cookies
  • Required: default true, required=false for optional