Returning different status codes in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What HTTP status code does this Spring Boot controller return?

Consider this Spring Boot controller method. What status code will the client receive when calling this endpoint?

Spring Boot

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

@RestController
public class MyController {
    @GetMapping("/check")
    public ResponseEntity<String> check() {
        return ResponseEntity.status(201).body("Created");
    }
}

A 200 OK

B 404 Not Found

C 201 Created

D 500 Internal Server Error

💡 Hint

Look at the status method used in ResponseEntity.

The method uses ResponseEntity.status(201) which sets the HTTP status code to 201 Created.

📝 Syntax

intermediate

Which option correctly returns a 404 status with a message in Spring Boot?

You want to return a 404 Not Found status with a message "User not found". Which code snippet is correct?

A return ResponseEntity.status(404).body("User not found");

B return ResponseEntity.notFound().body("User not found");

C return ResponseEntity.status(HttpStatus.NOT_FOUND, "User not found");

D return new ResponseEntity<>("User not found", 404);

💡 Hint

Check the ResponseEntity methods and constructors.

Option A correctly uses ResponseEntity.status(404).body(...) to set status and body. Option A is invalid because notFound() returns a ResponseEntity without a body() method. Option A is invalid syntax as there is no status(HttpStatus, Object) method. Option A uses invalid constructor arguments (expects HttpStatus, not int).

🔧 Debug

advanced

Why does this Spring Boot controller always return 200 OK instead of 400 Bad Request?

Look at this controller method. It tries to return 400 Bad Request on error but always returns 200 OK. Why?

Spring Boot

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

@RestController
public class ErrorController {
    @GetMapping("/error")
    public ResponseEntity<String> error(boolean hasError) {
        if (hasError) {
            return ResponseEntity.status(400).body("Bad Request");
        }
        return ResponseEntity.ok("All good");
    }
}

A The 400 ResponseEntity is created but not returned from the method.

B ResponseEntity.status(400) is invalid and defaults to 200.

C The method parameter 'hasError' is ignored by Spring Boot.

D The method must throw an exception to return 400 status.

💡 Hint

Check if the method returns the ResponseEntity created inside the if block.

The method creates a ResponseEntity with status 400 but does not return it. The method always returns ResponseEntity.ok("All good"), so status 200 is sent.

❓ state_output

advanced

What is the HTTP status code when this Spring Boot controller returns null body with 204 status?

This controller returns ResponseEntity with status 204 No Content and a null body. What will the client receive?

Spring Boot

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

@RestController
public class NoContentController {
    @GetMapping("/nocontent")
    public ResponseEntity<String> noContent() {
        return ResponseEntity.noContent().build();
    }
}

A 500 Internal Server Error

B 204 No Content with 'null' string body

C 200 OK with empty body

D 204 No Content with empty body

💡 Hint

Check what ResponseEntity.noContent().build() does.

ResponseEntity.noContent().build() returns a response with status 204 and no body content, so the client receives 204 No Content with empty body.

🧠 Conceptual

expert

Which option correctly demonstrates returning different status codes based on input in Spring Boot?

You want a controller method that returns 200 OK with "Success" if input is true, and 404 Not Found with "Not Found" if false. Which code snippet correctly implements this?

A

public ResponseEntity<String> check(boolean input) {
    return input ? ResponseEntity.ok("Success") : ResponseEntity.notFound().build();
}

B

public ResponseEntity<String> check(boolean input) {
    if (input) {
        return ResponseEntity.ok("Success");
    } else {
        return ResponseEntity.status(404).body("Not Found");
    }
}

C

public ResponseEntity<String> check(boolean input) {
    if (input) {
        return new ResponseEntity<>("Success", HttpStatus.OK);
    } else {
        return new ResponseEntity<>("Not Found", HttpStatus.NOT_FOUND);
    }
}

D

public ResponseEntity<String> check(boolean input) {
    if (input) {
        return ResponseEntity.ok("Success");
    }
    return ResponseEntity.notFound().body("Not Found");
}

💡 Hint

Check which options correctly set both status and body for 404 response.

Option B correctly returns 200 OK with body and 404 with body using fluent API. Option B is valid: ResponseEntity.notFound().build() returns 404 without body. Option B works but uses constructor style (requires HttpStatus import). Option B is invalid: notFound() has no body() method.

Practice

1. In Spring Boot, which class is commonly used to return different HTTP status codes from a controller?

easy

A. ResponseEntity

B. HttpStatusCode

C. HttpResponse

D. StatusCode

Solution

1. Step 1: Understand the purpose of ResponseEntity

   ResponseEntity is a Spring class that allows you to control the HTTP status code, headers, and body of the response.

2. Step 2: Identify the correct class for status codes

   HttpStatusCode, HttpResponse, and StatusCode are not standard Spring Boot classes for returning responses with status codes.

3. Final Answer:

   ResponseEntity -> Option A

4. Quick Check:

   Use ResponseEntity to return status codes [OK]

Hint: Use ResponseEntity to set status codes easily [OK]

Common Mistakes:

• Confusing ResponseEntity with HttpStatusCode
• Trying to return status codes without ResponseEntity
• Using non-existent classes like HttpResponse

2. Which of the following is the correct way to return a 404 Not Found status with a message in a Spring Boot controller?

easy

A. return new ResponseEntity("Not Found", 404);

B. return new ResponseEntity<>("Not Found", 404);

C. return ResponseEntity.status(404).body("Not Found");

D. return ResponseEntity(HttpStatus.NOT_FOUND, "Not Found");

Solution

1. Step 1: Check the syntax for ResponseEntity with status and body

   The method ResponseEntity.status(404).body("Not Found") correctly sets the status and body.

2. Step 2: Identify incorrect syntax options

   B uses a constructor with an int 404 instead of HttpStatus.NOT_FOUND. C uses an int instead of HttpStatus enum. D is not a valid constructor call.

3. Final Answer:

   return ResponseEntity.status(404).body("Not Found"); -> Option C

4. Quick Check:

   Use ResponseEntity.status().body() for custom status [OK]

Hint: Use ResponseEntity.status(code).body(message) [OK]

Common Mistakes:

• Using int instead of HttpStatus enum
• Incorrect constructor usage
• Missing method chaining for status and body

3. What will be the HTTP status code returned by this Spring Boot controller method?

public ResponseEntity<String> getUser(boolean found) {
    if (found) {
        return ResponseEntity.ok("User found");
    } else {
        return ResponseEntity.status(HttpStatus.NOT_FOUND).body("User not found");
    }
}

medium

A. 404 if found is true, 200 if false

B. Always 404

C. Always 200

D. 200 if found is true, 404 if false

Solution

1. Step 1: Analyze the if condition

   If found is true, the method returns ResponseEntity.ok("User found"), which means HTTP 200.

2. Step 2: Analyze the else condition

   If found is false, it returns ResponseEntity.status(HttpStatus.NOT_FOUND).body("User not found"), which means HTTP 404.

3. Final Answer:

   200 if found is true, 404 if false -> Option D

4. Quick Check:

   ResponseEntity.ok = 200, status(HttpStatus.NOT_FOUND) = 404 [OK]

Hint: ResponseEntity.ok = 200, status(HttpStatus.NOT_FOUND) = 404 [OK]

Common Mistakes:

• Mixing up true/false branches
• Assuming default status 200 always
• Confusing status codes with messages

4. Identify the error in this Spring Boot controller method that tries to return a 201 Created status:

public ResponseEntity<String> createItem() {
    return new ResponseEntity<>("Item created", 201);
}

medium

A. Cannot return ResponseEntity with a String body

B. Using int 201 instead of HttpStatus enum

C. ResponseEntity constructor requires three arguments

D. Missing @ResponseBody annotation

Solution

1. Step 1: Check ResponseEntity constructor parameters

   The constructor expects a body and an HttpStatus enum, not an int.

2. Step 2: Identify the incorrect use of status code

   Passing 201 as int causes a compilation error; should use HttpStatus.CREATED instead.

3. Final Answer:

   Using int 201 instead of HttpStatus enum -> Option B

4. Quick Check:

   Use HttpStatus.CREATED, not int 201 [OK]

Hint: Use HttpStatus enum, not int, for status codes [OK]

Common Mistakes:

• Passing int instead of HttpStatus enum
• Forgetting to import HttpStatus
• Assuming String body is invalid

5. You want to create a Spring Boot controller method that returns 201 Created when a new user is successfully added, 400 Bad Request if the input is invalid, and 401 Unauthorized if the user is not logged in. Which code snippet correctly implements this behavior?

hard

A. public ResponseEntity<String> addUser(boolean validInput, boolean loggedIn) {
if (!loggedIn) {
return ResponseEntity.status(HttpStatus.UNAUTHORIZED).body("Unauthorized");
}
if (!validInput) {
return ResponseEntity.status(HttpStatus.BAD_REQUEST).body("Invalid input");
}
return ResponseEntity.status(HttpStatus.CREATED).body("User created");
}

B. public ResponseEntity<String> addUser(boolean validInput, boolean loggedIn) {
if (!validInput) {
return ResponseEntity.status(HttpStatus.UNAUTHORIZED).body("Unauthorized");
}
if (!loggedIn) {
return ResponseEntity.status(HttpStatus.BAD_REQUEST).body("Invalid input");
}
return ResponseEntity.status(HttpStatus.CREATED).body("User created");
}

C. public ResponseEntity<String> addUser(boolean validInput, boolean loggedIn) {
if (!loggedIn) {
return new ResponseEntity<>("Unauthorized", 401);
}
if (!validInput) {
return new ResponseEntity<>("Invalid input", 400);
}
return new ResponseEntity<>("User created", 201);
}

D. }
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Solution

1. Step 1: Verify correct use of HttpStatus enums

   public ResponseEntity<String> addUser(boolean validInput, boolean loggedIn) { if (!loggedIn) { return ResponseEntity.status(HttpStatus.UNAUTHORIZED).body("Unauthorized"); } if (!validInput) { return ResponseEntity.status(HttpStatus.BAD_REQUEST).body("Invalid input"); } return ResponseEntity.status(HttpStatus.CREATED).body("User created"); } uses HttpStatus.UNAUTHORIZED, HttpStatus.BAD_REQUEST, and HttpStatus.CREATED enums correctly.

2. Step 2: Check logical order and syntax

   This code checks !loggedIn first, then !validInput, then returns 201. Options B, C, and D misuse status codes or pass ints to constructors instead of using HttpStatus enums.

3. Final Answer:

   Uses HttpStatus enums with correct logic: !loggedIn (401), !validInput (400), then 201 -> Option A

4. Quick Check:

   Use HttpStatus enums and correct logic order [OK]

Hint: Check login first, then input, use HttpStatus enums [OK]

Common Mistakes:

• Passing int status codes instead of HttpStatus enums
• Mixing up 400 and 401 status codes
• Incorrect order of condition checks