produces Attribute in @GetMapping — Restricting Response Content Type

Direct Answer

The produces attribute declares which response media types a handler method can produce. Spring includes it in request mapping and compares it with the request's Accept preferences during handler selection. If no selected handler can produce an acceptable representation, MVC normally returns 406 Not Acceptable. The value can be a media-type string or a constant whose value is that string.

Code Example

@RestController
@RequestMapping("/api/products")
public class ProductController {

    @GetMapping(value = "/{id}", produces = MediaType.APPLICATION_JSON_VALUE)
    public Product getProductJson(@PathVariable Long id) {
        // Only accepts requests with Accept: application/json
        return productService.findById(id);
    }

    @GetMapping(value = "/{id}/xml", produces = MediaType.APPLICATION_XML_VALUE)
    public Product getProductXml(@PathVariable Long id) {
        // Only accepts requests with Accept: application/xml
        return productService.findById(id);
    }

    @PostMapping(
        consumes = MediaType.APPLICATION_JSON_VALUE,
        produces = MediaType.APPLICATION_JSON_VALUE
    )
    public ResponseEntity<Product> createProduct(@RequestBody Product product) {
        // consumes: only accepts JSON request body (checks Content-Type)
        // produces: only returns JSON response (checks Accept)
        var saved = productService.save(product);
        return ResponseEntity.status(HttpStatus.CREATED).body(saved);
    }
}

Common Mistakes & Pitfalls

• Using hardcoded strings instead of constants: Writing produces = "application/json" instead of MediaType.APPLICATION_JSON_VALUE. The constant prevents typos and makes refactoring easier.
• Forgetting produces only filters GET/HEAD: For POST endpoints, you need both consumes (for request body) and produces (for response). Freshers often set only produces and wonder why their POST fails with 415 when sending JSON.
• Not understanding 406 vs 415: 406 means the Accept header doesn't match produces. 415 means the Content-Type doesn't match consumes. Freshers see these status codes and think it's a Spring bug instead of a header mismatch.
• Overly restrictive produces on all endpoints: Setting produces on every endpoint when you only return JSON creates maintenance overhead. Use it selectively where you need format constraints.