@Valid annotation on request body in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when @Valid fails on a request body?

Consider a Spring Boot controller method that uses @Valid on a request body object. What is the default behavior when the validation fails?

Spring Boot

public ResponseEntity<String> createUser(@Valid @RequestBody User user) {
    return ResponseEntity.ok("User created");
}

A The method returns HTTP 400 Bad Request with validation error details.

B The method proceeds normally and returns HTTP 200 OK.

C The method throws a NullPointerException.

D The method returns HTTP 500 Internal Server Error.

💡 Hint

Think about how Spring Boot handles validation exceptions by default.

When @Valid fails, Spring Boot automatically returns a 400 Bad Request response with details about the validation errors.

📝 Syntax

intermediate

Which code snippet correctly applies @Valid on a request body?

Select the code snippet that correctly uses @Valid to validate a request body in a Spring Boot controller.

A public ResponseEntity<String> add(@RequestBody User user) { return ResponseEntity.ok("Added"); }

B public ResponseEntity<String> add(@RequestBody @Valid User user) { return ResponseEntity.ok("Added"); }

C public ResponseEntity<String> add(@Valid User user) { return ResponseEntity.ok("Added"); }

D public ResponseEntity<String> add(User user) { return ResponseEntity.ok("Added"); }

💡 Hint

Remember that @Valid must be combined with @RequestBody to validate JSON input.

@Valid must be placed on the parameter annotated with @RequestBody to trigger validation of the incoming JSON.

🔧 Debug

advanced

Why does validation not trigger with @Valid on a request body?

Given this controller method, validation does not trigger even though @Valid is present. What is the most likely cause? public ResponseEntity updateUser(@RequestBody User user) { return ResponseEntity.ok("Updated"); }

Spring Boot

public ResponseEntity<String> updateUser(@RequestBody User user) {
    return ResponseEntity.ok("Updated");
}

A The method return type must be void for validation to work.

B The User class does not have any validation annotations.

C The controller method is missing @PostMapping annotation.

D The @Valid annotation is missing on the parameter.

💡 Hint

Check if the parameter is annotated with @Valid.

Validation only triggers if @Valid is present on the @RequestBody parameter.

❓ state_output

advanced

What is the response body when validation fails on a @Valid request body?

If a POST request sends invalid data to a Spring Boot controller method with @Valid on the request body, what does the response body contain by default?

A A JSON object listing field errors and messages.

B An empty response body with status 400.

C A plain text message 'Validation failed'.

D The original invalid JSON sent by the client.

💡 Hint

Think about how Spring Boot formats validation error responses.

Spring Boot returns a JSON response with details about each field that failed validation.

🧠 Conceptual

expert

How to customize validation error responses for @Valid request bodies?

Which approach allows customizing the error response sent when @Valid validation fails on a request body in Spring Boot?

A Add a @ResponseStatus annotation on the controller method.

B Override the toString() method of the request body class.

C Implement a @ControllerAdvice class with an @ExceptionHandler for MethodArgumentNotValidException.

D Use @JsonIgnore on all fields in the request body class.

💡 Hint

Think about global exception handling in Spring Boot.

Using @ControllerAdvice with @ExceptionHandler for MethodArgumentNotValidException lets you customize validation error responses.