14 Tips for Writing Spring MVC Controllers

1. Use @Controller Annotation

Declare a controller class with @Controller and map request URLs using @RequestMapping. The handler method returns a view name, e.g., "home".

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

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

2. Implement Controller Interface

Implement org.springframework.web.servlet.mvc.Controller and override handleRequest. This approach handles a single URL pattern defined in the Spring context.

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");
    }
}

3. Extend AbstractController

Extend AbstractController to gain support for HTTP methods, session handling, and caching. Override handleRequestInternal and configure bean properties such as supportedMethods.

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");
    }
}

4. Specify URL Mapping with @RequestMapping

Use @RequestMapping("/login") at class or method level to bind URLs. Multiple URLs can be mapped with an array syntax.

@RequestMapping({"/hello", "/hi", "/greetings"})
public String sayHello() { ... }

5. Define HTTP Methods

Set the method attribute of @RequestMapping to restrict handlers to GET, POST, etc.

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

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

6. Bind Request Parameters

Use @RequestParam to bind query or form parameters to method arguments, with optional required and defaultValue attributes.

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

7. Return ModelAndView

Handlers can return a view name as a String or a ModelAndView object to pass data to the view.

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

8. Add Objects to the Model

Use model.addObject(...) or a Map<String,Object> parameter to place data into the model.

modelView.addObject("listUser", listUser);
model.put("siteName", "CodeJava.net");

9. Perform Redirects

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

return new ModelAndView("redirect:/login");

10. Handle Form Submission and Validation

Annotate a method with @ModelAttribute to bind form fields to an object and use BindingResult for validation errors.

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

11. File Uploads

Spring binds uploaded files to CommonsMultipartFile[]. Iterate over the array and store each file.

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

12. Autowire Business Services

Inject service or DAO beans into controllers with @Autowired and delegate business logic.

@Controller
public class UserController {
    @Autowired
    private UserDAO userDAO;
    public String listUser() { userDAO.list(); }
    public String saveUser(User user) { userDAO.save(user); }
}

13. Access HttpServletRequest/Response

Add HttpServletRequest and HttpServletResponse parameters to a handler to work with low‑level servlet APIs.

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

14. Follow Single‑Responsibility Principle

Keep controllers thin by delegating business work to services, and create separate controllers for distinct domains (e.g., UserController, OrderController).