[Solved] You want to implement a REST API in Spring Boot that updates a product's price only if the product exists,... Which combination of annotations and code best achieves this using @PutMapping? | Spring Boot

Spring Boot - REST Controllers

You want to implement a REST API in Spring Boot that updates a product's price only if the product exists, otherwise returns 404. Which combination of annotations and code best achieves this using @PutMapping?

A@PutMapping("/products/{id}") public Product updatePrice(@RequestParam int id, @RequestBody Product p) { p.setId(id); return productService.save(p); }

B@PutMapping("/products") public Product updatePrice(@RequestBody Product p) { productService.save(p); return p; }

C@PutMapping("/products/{id}") public void updatePrice(@PathVariable int id, @RequestBody Product p) { productService.save(p); }

D

@PutMapping("/products/{id}") public ResponseEntity<Product> updatePrice(@PathVariable int id, @RequestBody Product p) {
    return productService.findById(id)
        .map(existing -> {
            existing.setPrice(p.getPrice());
            productService.save(existing);
            return ResponseEntity.ok(existing);
        })
        .orElse(ResponseEntity.notFound().build());
}

Step-by-Step Solution

Solution:

Step 1: Check for product existence before update
@PutMapping("/products/{id}") public ResponseEntity updatePrice(@PathVariable int id, @RequestBody Product p) { return productService.findById(id) .map(existing -> { existing.setPrice(p.getPrice()); productService.save(existing); return ResponseEntity.ok(existing); }) .orElse(ResponseEntity.notFound().build()); } uses productService.findById(id) to check if product exists, returning 404 if not.
Step 2: Update price only if product found and return proper HTTP response
The map lambda updates the price on the existing product, saves it, and returns ResponseEntity.ok(existing); orElse returns notFound().
Final Answer:
@PutMapping("/products/{id}") public ResponseEntity updatePrice(@PathVariable int id, @RequestBody Product p) { return productService.findById(id) .map(existing -> { existing.setPrice(p.getPrice()); productService.save(existing); return ResponseEntity.ok(existing); }) .orElse(ResponseEntity.notFound().build()); } -> Option D
Quick Check:
Check existence, update, return 404 if missing [OK]

Quick Trick: Check existence first, then update and return ResponseEntity [OK]

Common Mistakes:

Not checking if product exists before update
Using @RequestParam instead of @PathVariable for ID
Not returning 404 when product missing

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Which combination of annotations and code best achieves this using @PutMapping?

Step 1: Check for product existence before update

Step 2: Update price only if product found and return proper HTTP response

Final Answer:

Quick Check:

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