Returning different status codes in Spring Boot - Step-by-Step Execution

Concept Flow - Returning different status codes

Client sends HTTP request

↓

Controller method receives request

↓

Process request logic

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Decide status code to return

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Return 200

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Client receives response with status code

The server receives a request, processes it, decides which HTTP status code fits the result, and sends that code back to the client.

Execution Sample

Spring Boot

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {

  @GetMapping("/status/{code}")
  public ResponseEntity<String> getStatus(@PathVariable int code) {
    return switch (code) {
      case 200 -> ResponseEntity.ok("OK");
      case 404 -> ResponseEntity.status(404).body("Not Found");
      case 500 -> ResponseEntity.status(500).body("Server Error");
      default -> ResponseEntity.badRequest().body("Invalid code");
    };
  }
}

This controller method returns different HTTP status codes and messages based on the input code.

Execution Table

Step	Input code	Condition matched	ResponseEntity status	Response body
1	200	case 200	200 OK	"OK"
2	404	case 404	404 Not Found	"Not Found"
3	500	case 500	500 Server Error	"Server Error"
4	123	default	400 Bad Request	"Invalid code"
5	-	No more inputs	-	-

💡 Execution stops after returning the response for the given input code.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
code	N/A	200	404	500	123	123
ResponseEntity.status	N/A	200	404	500	400	400
ResponseEntity.body	N/A	"OK"	"Not Found"	"Server Error"	"Invalid code"	"Invalid code"

Key Moments - 2 Insights

Why does the method return different status codes instead of always 200?

Because the method uses a switch on the input code to decide which HTTP status to send back, as shown in execution_table rows 1-4.

What happens if the input code is not 200, 404, or 500?

The default case runs, returning a 400 Bad Request status with message "Invalid code", as seen in execution_table row 4.

Visual Quiz - 3 Questions

Look at the execution_table, what is the ResponseEntity status when input code is 404?

A 500 Server Error

B 200 OK

C 404 Not Found

D 400 Bad Request

💡 Hint

Check execution_table row 2 under 'ResponseEntity status'

At which step does the method return a 400 Bad Request status?

A Step 1

B Step 4

C Step 3

D Step 2

💡 Hint

Look at execution_table row 4 for the default case

If the input code is changed to 200, what will be the response body?

A "OK"

B "Server Error"

C "Not Found"

D "Invalid code"

💡 Hint

Refer to execution_table row 1 under 'Response body'

Concept Snapshot

In Spring Boot, use ResponseEntity to return different HTTP status codes.
Use ResponseEntity.ok() for 200 OK.
Use ResponseEntity.status(code).body(message) for other codes.
Switch or if-else decides which status to send.
This helps client know result type clearly.

Full Transcript

This example shows how a Spring Boot controller method returns different HTTP status codes based on input. The method uses a switch statement on the input code. For 200, it returns ResponseEntity.ok with message "OK". For 404, it returns status 404 with "Not Found". For 500, it returns status 500 with "Server Error". For any other code, it returns 400 Bad Request with "Invalid code". The execution table traces each input and the response status and body returned. The variable tracker shows how the input code and response values change step by step. Key moments clarify why different codes are returned and what happens on unknown codes. The quiz tests understanding of which status and body correspond to which input code. This helps beginners see how to control HTTP responses clearly in Spring Boot.