@RestController — Spring Technical Interview Questions & Answers

Combines @Controller and @ResponseBody for JSON APIs.

@RestController

  • @RestController builds JSON APIs easily.
  • It is @Controller + @ResponseBody combined.
  • Return objects/lists; Boot converts them to JSON.
  • Use it for APIs; use @Controller when you return HTML views.
  • @RestController = web API controller that writes the response body.

Technical Interview Tip: Contrast @RestController vs @Controller.

Code Examples for @RestController

@RestController — working example

import java.util.Map;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

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

  @GetMapping("/{id}")
  ResponseEntity<String> get(@PathVariable Long id) {
    return ResponseEntity.ok("user-" + id);
  }

  @GetMapping
  String byRole(@RequestParam(defaultValue = "user") String role) {
    return "role=" + role;
  }

  @PostMapping
  ResponseEntity<String> create(@RequestBody Map<String, String> body) {
    return ResponseEntity.status(201).body("created:" + body.get("email"));
  }
}

@RestController = API JSON/text; @PathVariable from URI, @RequestParam from query, @RequestBody from JSON body.

How to Explain @RestController to an Interviewer

What is @RestController (sb)?

Used for GET /api/marks/{roll} a campus API Not just the heading

Give one small example of @RestController (sb).

@RestController + service call Combines @Controller and @ResponseBody for JSON APIs

What mistake do beginners make with @RestController (sb)?

business logic inside the controller Show the fix

Where do you use @RestController (sb)?

a campus API GET /api/marks/{roll}