@Controller & @RestController

Introduction

In Spring Boot, a controller is a component that handles HTTP requests and produces responses. Spring provides two main annotations: @Controller and @RestController.

@Controller

@Controller is used on a class responsible for handling requests. It's usually combined with @ResponseBody on methods to return data directly (rather than a view name).

@Controller
@RequestMapping("/students")
public class StudentController {

    @ResponseBody
    @GetMapping("/{id}")
    public Student getById(@PathVariable Long id) {
        return studentService.findById(id);
    }
}

Without @ResponseBody, the return value is interpreted as a view (template) name.

@RestController

@RestController is a shorthand for @Controller + @ResponseBody at the class level. All methods automatically return data (JSON/XML), not a view name.

@RestController
@RequestMapping("/api/students")
public class StudentRestController {

    @GetMapping
    public List<Student> getAll() {
        return studentService.findAll();
    }

    @PostMapping
    public Student create(@RequestBody Student student) {
        return studentService.save(student);
    }
}

Key Differences

Feature	@Controller	@RestController
Default return type	View name (String)	Response body (Object/JSON)
Requires @ResponseBody	Yes, per method	No, automatic
Best for	MVC + Thymeleaf	REST API
Content type	HTML	JSON / XML

@ResponseStatus

This annotation sets the HTTP status code that is returned.

@PostMapping
@ResponseStatus(HttpStatus.CREATED)
public Student create(@RequestBody Student student) {
    return studentService.save(student);
}

Return Type: ResponseEntity

ResponseEntity gives you full control over the status code, headers, and response body.

@GetMapping("/{id}")
public ResponseEntity<Student> getById(@PathVariable Long id) {
    return studentService.findById(id)
        .map(ResponseEntity::ok)
        .orElse(ResponseEntity.notFound().build());
}

Return Type	Use Case
`ResponseEntity<T>`	Full control (status, headers, body)
`T` (Object)	Spring automatically serializes to JSON
`String`	Plain text response
`void`	Status 200 only, no body

Simple CRUD Example

@RestController
@RequestMapping("/api/users")
public class UserController {

    @GetMapping
    public List<User> index() {
        return userService.getAll();
    }

    @GetMapping("/{id}")
    public User show(@PathVariable Long id) {
        return userService.getById(id);
    }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public User store(@RequestBody User user) {
        return userService.save(user);
    }

    @PutMapping("/{id}")
    public User update(@PathVariable Long id, @RequestBody User user) {
        return userService.update(id, user);
    }

    @DeleteMapping("/{id}")
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public void destroy(@PathVariable Long id) {
        userService.delete(id);
    }
}

Summary

Use @RestController for REST API (JSON).
Use @Controller for MVC (HTML/templates).
ResponseEntity is a good fit when you need flexible responses.

Next chapter: We'll take a closer look at Request Mapping — how to define the path, method, and parameters of an endpoint.