14 Essential Tips for Writing Spring MVC Controllers

In Spring MVC a controller class handles client requests, delegates business logic to service classes, and returns a logical view name that the DispatcherServlet resolves to render the result.

1. Use @Controller annotation

The simplest way to create a controller is to annotate a class with @Controller. Example:

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class HomeController {
    @RequestMapping("/")
    public String visitHome() {
        return "home";
    }
}

When annotation‑driven configuration is enabled ( <annotation-driven/>) Spring scans the specified base package for such classes.

2. Implement the Controller interface

Another classic approach is to implement the Controller interface and override handleRequest:

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;

public class MainController implements Controller {
    @Override
    public ModelAndView handleRequest(HttpServletRequest request,
                                      HttpServletResponse response) throws Exception {
        System.out.println("Welcome main");
        return new ModelAndView("main");
    }
}

Note that a class implementing this interface can handle only a single URL pattern.

3. Extend AbstractController

Extending AbstractController allows easy configuration of supported HTTP methods, session handling, and caching:

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.AbstractController;

public class BigController extends AbstractController {
    @Override
    protected ModelAndView handleRequestInternal(HttpServletRequest request,
                                                 HttpServletResponse response) throws Exception {
        System.out.println("You're big!");
        return new ModelAndView("big");
    }
}

Bean definition can specify supported methods, e.g. supportedMethods="POST".

4. Specify URL mapping with @RequestMapping

The @RequestMapping annotation maps a URL pattern to a controller class or method:

@RequestMapping("/login")
public class LoginController { ... }

When placed at the class level the controller becomes a single‑action controller.

5. Define HTTP request method

Use the method attribute of @RequestMapping to restrict handling to specific HTTP verbs:

@Controller
@RequestMapping("/login")
public class LoginController {
    @RequestMapping(method = RequestMethod.GET)
    public String viewLogin() { return "LoginForm"; }

    @RequestMapping(method = RequestMethod.POST)
    public String doLogin() { return "Home"; }
}

6. Map request parameters with @RequestParam

Bind request parameters directly to method arguments:

@RequestMapping(value = "/login", method = RequestMethod.POST)
public String doLogin(@RequestParam String username,
                       @RequestParam String password) { ... }

Attributes such as required and defaultValue control validation and defaults.

7. Return ModelAndView

A handler can return a view name as a String or a ModelAndView object when additional data is needed:

@RequestMapping("/listUsers")
public ModelAndView listUsers() {
    List<User> list = new ArrayList<>(); // fetch from DAO
    ModelAndView mv = new ModelAndView("UserList");
    mv.addObject("listUser", list);
    return mv;
}

8. Put objects into the model

Use ModelAndView.addObject or a Map<String,Object> parameter to expose data to the view:

public String viewStats(Map<String,Object> model) {
    model.put("siteName", "CodeJava.net");
    model.put("pageviews", 320000);
    return "Stats";
}

9. Perform redirects

Return a view name prefixed with redirect:/ to send the client to another URL:

if (!isLogin) {
    return new ModelAndView("redirect:/login");
}

10. Handle form submission with @ModelAttribute

Bind form fields to a command object and validate with BindingResult:

@Controller
public class RegistrationController {
    @RequestMapping(value="/doRegister", method=RequestMethod.POST)
    public String doRegister(@ModelAttribute("userForm") User user,
                             BindingResult result) {
        if (result.hasErrors()) {
            // handle errors
        }
        // registration logic
        return "Success";
    }
}

11. File upload handling

Spring binds uploaded files to CommonsMultipartFile[] parameters:

@RequestMapping(value="/uploadFiles", method=RequestMethod.POST)
public String handleFileUpload(@RequestParam CommonsMultipartFile[] fileUpload) throws Exception {
    for (CommonsMultipartFile f : fileUpload) {
        f.transferTo(new File(f.getOriginalFilename()));
    }
    return "Success";
}

12. Autowire business classes

Inject service or DAO beans into a controller with @Autowired:

@Controller
public class UserController {
    @Autowired
    private UserDAO userDAO;

    public String listUser() { userDAO.list(); }
    public String saveUser(User u) { userDAO.save(u); }
    public String deleteUser(User u) { userDAO.delete(u); }
    public String getUser(int id) { userDAO.get(id); }
}

13. Access HttpServletRequest and HttpServletResponse

Simply declare the servlet objects as method parameters to obtain direct access:

@RequestMapping("/download")
public String doDownload(HttpServletRequest request, HttpServletResponse response) {
    // use request/response streams
    return "DownloadPage";
}

14. Follow the Single Responsibility Principle

Keep controllers thin by delegating business logic to service classes and create separate controllers for distinct domains (e.g., UserController, OrderController, PaymentController).