Custom Validation Annotations in Spring
1. Define the Custom Validation AnnotationCustom Validation Annotations in Spring
First, you need to define a custom annotation. This annotation should be marked with @Constraint
and specify a class that implements the ConstraintValidator
interface as its validator.
1 | import javax.validation.Constraint; |
@Constraint(validatedBy = CourseCodeConstraintValidator.class)
: Specifies thatCourseCode
is a constraint annotation and its validation logic is implemented byCourseCodeConstraintValidator
.@Target({ElementType.METHOD, ElementType.FIELD})
: Indicates that the annotation can be applied to methods and fields.@Retention(RetentionPolicy.RUNTIME)
: Ensures that the annotation is available at runtime.public Class<?>[] groups() default {};
: Used to specify validation groups.public Class<? extends Payload>[] payload() default {};
: Used to provide custom payload objects for the validation.
2. Create the Custom Validator
Next, create a class that implements the ConstraintValidator
interface. This class contains the actual validation logic.
1 | import javax.validation.ConstraintValidator; |
CourseCodeConstraintValidator
implementsConstraintValidator<CourseCode, String>
.initialize
method is used to read thevalue
attribute from the annotation.isValid
method contains the validation logic.
3. Apply the Custom Annotation
Apply the custom annotation to the fields that need to be validated.
1 | import javax.validation.constraints.NotNull; |
4. Integrate with Spring MVC
In the Spring MVC controller, use the @Valid
annotation to trigger the validation process.
1 | import org.springframework.stereotype.Controller; |
@Valid
: Enables automatic validation of theCustomer
object.@ModelAttribute("customer") Customer theCustomer
: Binds form data to theCustomer
object and validates it.BindingResult theBindingResult
: Captures the validation errors.
By following these steps, you can create and use custom validation annotations in a Spring application to ensure that your data meets specific validation criteria.