How to Use @Valid Annotation in Spring Boot for Validation

In Spring Boot, use the @Valid annotation on method parameters like request bodies or form objects to trigger automatic validation based on constraints. Combine it with @RequestBody and constraint annotations (e.g., @NotNull) on your model fields to validate input data before processing.

Syntax

The @Valid annotation is placed on a method parameter in a controller to activate validation. It works with Java Bean Validation annotations on the object's fields.

• @Valid: Triggers validation on the annotated parameter.
• @RequestBody: Binds HTTP request JSON to a Java object.
• Constraint annotations (e.g., @NotNull, @Size): Define validation rules on fields.

java

public ResponseEntity<String> createUser(@Valid @RequestBody User user) {
    // method body
}

Example

This example shows a Spring Boot REST controller that validates a User object sent in the request body. If validation fails, Spring Boot returns a 400 Bad Request with error details.

java

import jakarta.validation.Valid;
import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.Email;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {

    public static class User {
        @NotBlank(message = "Name must not be blank")
        private String name;

        @Email(message = "Email should be valid")
        private String email;

        // Getters and setters
        public String getName() { return name; }
        public void setName(String name) { this.name = name; }
        public String getEmail() { return email; }
        public void setEmail(String email) { this.email = email; }
    }

    @PostMapping("/users")
    public ResponseEntity<String> createUser(@Valid @RequestBody User user) {
        return ResponseEntity.ok("User is valid: " + user.getName());
    }
}

Output

HTTP 200 OK with body: "User is valid: [name]" if valid

HTTP 400 Bad Request with validation error details if invalid

Common Pitfalls

• Forgetting to add @Valid means validation won't run automatically.
• Not using @RequestBody or wrong parameter type can cause binding errors.
• Missing constraint annotations on fields means no validation rules.
• Not handling validation errors can lead to unclear responses; Spring Boot handles this by default but can be customized.

java

/* Wrong: Missing @Valid - validation is skipped */
@PostMapping("/users")
public ResponseEntity<String> createUser(@RequestBody User user) {
    return ResponseEntity.ok("User is valid: " + user.getName());
}

/* Right: Add @Valid to trigger validation */
@PostMapping("/users")
public ResponseEntity<String> createUser(@Valid @RequestBody User user) {
    return ResponseEntity.ok("User is valid: " + user.getName());
}

Quick Reference

Use this quick guide to remember how to apply @Valid in Spring Boot:

Step	Description
1	Add @Valid before the method parameter to validate.
2	Use @RequestBody to bind JSON to the object.
3	Annotate model fields with validation constraints like @NotNull, @Size, @Email.
4	Handle validation errors automatically or customize error responses.
5	Ensure jakarta.validation dependency is included in your project.

Key Takeaways

Add @Valid on controller method parameters to enable automatic validation.

Use constraint annotations on model fields to define validation rules.

Combine @Valid with @RequestBody for JSON input validation.

Spring Boot returns 400 Bad Request automatically if validation fails.

Always include the Jakarta Bean Validation dependency in your project.