In this quick article, we will discuss one important interview question that is what is the difference between @Controller vs @RestController in Spring.

@Controller vs @RestController in Spring

The main difference between the @Controller and @RestController annotations is that the @ResponseBody annotation is automatically included in the @RestController. This means that we don't need to annotate our handler methods with the @ResponseBody. We need to do this in a @Controller class if we want to write response type directly to the HTTP response body (Ex: JSON or XML).

@Controller annotation example: in the below code snippet notice the @ResponseBody added to each of the handler methods in the return value.

@RequestMapping("/api/v1")
public class EmployeeController {
    @Autowired
    private EmployeeRepository employeeRepository;

    @GetMapping("/employees")
    public @ResponseBody List<Employee> getAllEmployees() {
       // logic goes here
    }

    @GetMapping("/employees/{id}")
    public @ResponseBody ResponseEntity<Employee> getEmployeeById(@PathVariable(value = "id") Long employeeId)
        throws ResourceNotFoundException {
        // logic goes here
    }
    
    @PostMapping("/employees")
    public @ResponseBody Employee createEmployee(@Valid @RequestBody Employee employee) {
        // logic goes here
    }

    @PutMapping("/employees/{id}")
    public @ResponseBody ResponseEntity<Employee> updateEmployee(@PathVariable(value = "id") Long employeeId,
         @Valid @RequestBody Employee employeeDetails) throws ResourceNotFoundException {
        // logic goes here
    }

    @DeleteMapping("/employees/{id}")
    public @ResponseBody Map<String, Boolean> deleteEmployee(@PathVariable(value = "id") Long employeeId)
         throws ResourceNotFoundException {
       // logic goes here
    }
}

To use @RestController in the above example, all we need to do is modify the @Controller to @RestController and remove the @ResponseBody from each method. The resultant class should look like the following:

@RestController
@RequestMapping("/api/v1")
public class EmployeeController {
    @Autowired
    private EmployeeRepository employeeRepository;

    @GetMapping("/employees")
    public List<Employee> getAllEmployees() {
         // logic goes here
    }

    @GetMapping("/employees/{id}")
    public ResponseEntity<Employee> getEmployeeById(@PathVariable(value = "id") Long employeeId)
        throws ResourceNotFoundException {
       // logic goes here
    }
    
    @PostMapping("/employees")
    public Employee createEmployee(@Valid @RequestBody Employee employee) {
        // logic goes here
    }

    @PutMapping("/employees/{id}")
    public ResponseEntity<Employee> updateEmployee(@PathVariable(value = "id") Long employeeId,
         @Valid @RequestBody Employee employeeDetails) throws ResourceNotFoundException {
       // logic goes here
    }

    @DeleteMapping("/employees/{id}")
    public Map<String, Boolean> deleteEmployee(@PathVariable(value = "id") Long employeeId)
         throws ResourceNotFoundException {
        // logic goes here
    }
}

@RestController is a combination @Controller and @ResponseBody annotations.

References

Top 10 Spring MVC Interview Questions and Answers