Using javax.validation Annotations for Parameter Validation in Spring Boot

The article introduces the pain of manual parameter validation in Java applications and explains why using javax.validation annotations simplifies validation in Spring Boot.

It shows a verbose example of serial validation with multiple if‑else checks and then demonstrates how to replace it with annotation‑driven validation using constraints such as @NotNull , @NotBlank , @Pattern , etc.

Dependency snippets for JSR‑303 and Hibernate Validator are provided.

A table lists common validation annotations and their target data types.

Practical code examples cover:

Declaring @Validated on controller methods.

Annotating a DTO ( UserDTO ) with constraints, including custom messages and groups.

Creating a custom annotation @IdentityCardNumber and its validator class.

Using validation groups ( Create , Update ) to apply different rules for create and update operations.

Handling validation exceptions globally with GlobalExceptionHandler .

Validating request parameters directly in method signatures.

The article concludes that annotation‑based validation reduces boiler‑plate code, improves error handling, and encourages a unified response structure.