Category: React • Beginner
Published on 06 Apr 2026
Explanation
Spring Boot field validation ensures incoming request data is correct before processing. It helps prevent invalid input such as empty fields, wrong email format, or short passwords.
Code Example
// Add dependency (Maven) <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-validation </artifactId> </dependency>
Explanation
Validation annotations are added inside DTO classes to define rules like required fields, email format, or minimum length.
Code Example
import jakarta.validation.constraints.*;
public class StudentDTO {
@NotBlank(message = "Name is required")
private String name;
@Email(message = "Invalid email format")
private String email;
@Size(min = 6, message = "Password
must be at least 6 characters")
private String password;
}
Explanation
@Valid annotation is used in controller methods to trigger validation automatically when request data is received.
Code Example
import org.springframework.web.
bind.annotation.*;
import jakarta.validation.Valid;
@RestController
@RequestMapping("/students")
public class StudentController {
@PostMapping
public String createStudent(
@Valid @RequestBody StudentDTO studentDTO) {
return "Student created
successfully";
}
}
Explanation
Common validation annotations include @NotNull, @NotBlank, @Email, @Size, @Min, and @Max to enforce input constraints.
Code Example
public class UserDTO {
@NotNull(message = "ID cannot be null")
private Long id;
@NotBlank(message = "Username required")
private String username;
@Min(value = 18,
message = "Minimum age is 18")
private int age;
}
Explanation
Validation errors can be captured using BindingResult to return custom error messages instead of default responses.
Code Example
import org.springframework.
validation.BindingResult;
@PostMapping("/register")
public Object registerUser(@Valid
@RequestBody
UserDTO userDTO, BindingResult result) {
if(result.hasErrors()) {
return result.getAllErrors();
}
return "User registered successfully";
}
Explanation
Field validation improves API reliability and security by preventing invalid or incomplete data from entering backend systems such as student registration or certificate workflows in training platforms 🎓.
Code Example
@NotBlank(message = "Course name required") private String courseName;