Spring Boot: integrating Bean Validation between Spring and Hibernate (supporting DI on custom validations with Hibernate)

BeanValidationConfig.java

@Configuration
public class BeanValidationConfig {

    /**
     * The idea here is to configure Hibernate to use the same ValidatorFactory used by Spring,  
     * so that Hibernate will be able to handle custom validations that need to use dependency injection (DI)
     */
    @Bean
    public HibernatePropertiesCustomizer hibernatePropertiesCustomizer(final Validator validator) {
        return new HibernatePropertiesCustomizer() {
            @Override
            public void customize(Map<String, Object> hibernateProperties) {
                hibernateProperties.put("javax.persistence.validation.factory", validator);
            }
        }; // or replace with lambda: return hibernateProperties -> hibernateProperties.put("javax.persistence.validation.factory", validator);
    }
}

Some interesting links:

• https://stackoverflow.com/questions/2712345/jsr-303-dependency-injection-and-hibernate
• https://stackoverflow.com/questions/56782292/configuring-spring-validation-and-hibernate-validation
• https://docs.spring.io/spring-boot/docs/2.3.0.RELEASE/api/org/springframework/boot/autoconfigure/orm/jpa/HibernatePropertiesCustomizer.html
• https://docs.spring.io/spring-boot/docs/current/api/org/springframework/boot/autoconfigure/orm/jpa/EntityManagerFactoryBuilderCustomizer.html
• https://github.com/andyrbell/hibernate-properties-customizer-example/blob/master/src/main/java/com/example/hibernatemetadata/config/HibernateConfig.java

It's important to notice that your custom validation may be executed on persist and merge/update operations inside the same transaction, what may be too expensive in some cases (depending on the logic inside your validator):

@Transactional
public void create(Product product) {

    entityManager.persist(product); // validation will be executed here
   
     // ... some business logic
     product.setNsu(nsuGenerator.generate()); 
     entityManager.merge(product); // validation will be executed here again
}

If you want to execute your custom validation (or any validation) only on persist, you can use Validation Groups as discussed on this thread in Stack Overflow.

Here is a very good explanation about why Bean Validation with Hibernate does not support dependency injection (DI) by default: Video Dev Eficiente: Como funciona a integração entre o Spring e a Bean Validation