Spring boot validation annotations @Valid and @NotBlank not working

If you are facing this problem in latest version of spring boot (2.3.0) make sure to add the following dependency:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
</dependency>

Observation:
In earlier version of Spring Boot (1.4.7), javax.validation used to work out of the box. But, after upgrading to latest version, annotations broke. Adding the following dependency alone doesn’t work:

<dependency>
    <groupId>javax.validation</groupId>
    <artifactId>validation-api</artifactId>
</dependency>

Because this provides JSR Specification but not the implementation. You can also use hibernate-validator instead of spring-boot-starter-validation.