Model in Spring MVC — Passing Data from Controller to View

Direct Answer

In Spring MVC, Model is a holder for attributes exposed to a view during server-side rendering. A controller adds values and returns a view name; the selected view reads those attributes. A Java object returned from a @RestController is not 'the Model' in this sense—it is a handler return value written to the response body by an HttpMessageConverter.

Code Example

// Traditional MVC controller - uses Model for view rendering
@Controller
public class ProductController {
    @GetMapping("/products/{id}")
    public String showProduct(@PathVariable Long id, Model model) {
        var product = productService.findById(id);
        model.addAttribute("product", product); // Add to Model
        model.addAttribute("categories", categoryService.findAll());
        return "product-details"; // View name - Thymeleaf template
    }
}

// REST controller - no Model needed, return object directly
@RestController
@RequestMapping("/api/products")
public class ProductApiController {
    @GetMapping("/{id}")
    public Product getProduct(@PathVariable Long id) {
        return productService.findById(id); // Auto-serialized to JSON
    }
}

// In Thymeleaf template (product-details.html):
// <h1 th:text="${product.name}">Product Name</h1>
// The ${product} accesses the Model attribute we added

Common Mistakes & Pitfalls

• Using Model in REST controllers: Freshers add Model parameters to @RestController methods thinking they need it for JSON responses. Spring REST doesn't use views, so Model attributes are ignored — just return the object directly.
• Confusing Model with Model layer: Saying "the Model handles business logic" mixes Spring's Model interface with the MVC architectural pattern's Model layer (services/entities). Spring's Model is just a data container.
• Overloading Model with services: Adding service objects to Model instead of the data they produce. The view needs data (a User object), not the UserService itself. Pass model.addAttribute("user", userService.getUser()), not the service.