javax validation constraints not working in Spring Boot

Question

I cannot get annotations such as @NotEmpty, @NotBlank and @NotNull to fire in my Spring Boot application.

I've followed this (maven) example:

https://spring.io/guides/gs/validating-form-input/

...and I don't see what I am doing wrong.

POJO:

import javax.validation.constraints.NotBlank;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class College
{    
    @NotBlank
    private String collegeCode;
.
.
.

Spring controller:

@RequestMapping(value="/addCollege", method = RequestMethod.POST) 
public String addCollege(@Valid @ModelAttribute("college") College college, BindingResult bindingResult, Model model, HttpSession session)
{
    if(bindingResult.hasErrors()) //this is never true
    {
        logger.debug("Errors when adding new college!!!");
        return "admin/colleges/addCollege";
    }
    collegeProcessor.saveCollege(college);
    return getAllColleges(model, session);
}

Screen:

<form action="#" th:action="${addOrEdit} == 'add' ? @{/addCollege} : @{/updateCollege}" th:object="${college}" method="post">

    <table class="table">

        <tr>
            <td>College Code</td>
            <td><input size="10" name="collegeCode" th:field="*{collegeCode}"/></td>
            <div id="errors" th:if="${#fields.hasErrors('collegeCode')}" th:errors="*{collegeCode}"></div>
        </tr>
.
.
.

As well as @NotBlank, I have tried @NotEmpty and @NotNull, but the same thing happens. My screen does not validate the input, and allows a college object with an empty collegeCode to be saved.

The interesting thing is if I change my POJO to use the deprecated Hibernate validator instead...

import org.hibernate.validator.constraints.NotBlank;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class College
{
    @NotBlank
    private String collegeCode;
.
.
.

...then the validation DOES fire, and the screen prevents me from saving a College object with an empty collegeCode.

Can anyone tell me why my validation doesn't work when using the javax.validation.constraints validators?

Answer 1

Include Maven dependency for 2.3.0.RELEASE in pom.xml, however, it is not required for lower version of Spring Boot Application.

<!-- https://mvnrepository.com/artifact/javax.validation/validation-api -->
<dependency>
  <groupId>javax.validation</groupId>
  <artifactId>validation-api</artifactId>
</dependency>

Answer 2

Since version 2.3.0.RELEASE the validation starter is not included in web/webflux starters by default, you need to add it manually. More details here

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