@Autowired bean null in ConstraintValidator when invoked by Sessionfactory.getCurrentSession.merge

Question

I have just implemented Bean Validation with Hibernate.

If I call the validator explicitly it works as expected and my @Autowired DAO bean that connects to the DB is inj

Answer 1

Ok after about 18hrs of googling I finally came across a site that both described the problem it has a solution. Recipe: Using Hibernate event-based validation with custom JSR-303 validators and Spring autowired injection

In my current project, we wanted to build a custom validator that would check if an e-mail address already existed in the database before saving any instance of our Contact entity using Hibernate. This validator needed a DAO to be injected in order to check for the existence of the e-mail address in the database. To our surprise, what we thought would be a breeze was more of a gale. Spring’s injection did not work at all when our bean was validated in the context of Hibernate’s event-based validation (in our case, the pre-insert event).

In the end my spring configuration ended up looking like this:

...
<bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean" />
<bean id="beanValidationEventListener" class="org.hibernate.cfg.beanvalidation.BeanValidationEventListener">
    <constructor-arg ref="validator"/>
    <constructor-arg ref="hibernateProperties"/>
</bean>

...

<util:properties id="hibernateProperties" location="classpath:hibernate.properties"/>

<bean id="sessionFactory"
    class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
    <property name="dataSource" ref="myDataSource" />
    <property name="packagesToScan" value="com.twoh" />
    <property name="hibernateProperties" ref="hibernateProperties"/>
    <property name="eventListeners">
        <map>
            <entry key="pre-insert" value-ref="beanValidationEventListener" />
            <entry key="pre-update" value-ref="beanValidationEventListener" />
        </map>
    </property>
</bean>

Answer 2

You can use the following method provided by Spring framework since 2.5.1

SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);

it's much cleaner since you don't have to set any listener/property across your application.

You code will look like this:

public class ValidUniqueUserEmailValidator implements ConstraintValidator<ValidUniqueUserEmail, Object>, Serializable {

    private static final long serialVersionUID = 1L;

    @Autowired
    private UserDAO userDAO;

    @Override
    public void initialize(ValidUniqueUserEmail constraintAnnotation) {
        SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);
    }

    @Override
    public boolean isValid(Object value, ConstraintValidatorContext context) {
        boolean isValid = true;
        if (value instanceof String) {
            String email = value.toString();
            if (email == null || email.equals("")) {
                isValid = false;
            }else{
                User user = new User();
                user.setEmail(email);
                isValid = (userDAO.countByEmail(user) > 0);
            }
        }
        return isValid;

    }

}

Hope it helps you guys out