Question

I am in need of a custom constraint which validates that a value is unique. I have been searching the internet for a long time to find a good example. The one I found is using hibernate template which is not recommended anymore so I was wondering if anyone had the expertise to “translate” this code so that it doesn’t use the templates. I have tried to do it myself but I don’t understand what the getter and setter are for. Here is the code which I got from this helpful guide.

package com.omgo.security.domain.validator;

import java.io.Serializable;
import java.util.List;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import org.hibernate.SessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.orm.hibernate3.HibernateTemplate;

public class UniqueIDValidator implements ConstraintValidator<Unique, Serializable> {

HibernateTemplate hibernateTemplate;

private Class<?> entityClass;
private String uniqueField;

public void initialize(Unique unique) {
    entityClass = unique.entity();
    uniqueField = unique.property();
}

public boolean isValid(Serializable property, ConstraintValidatorContext cvContext) {

    String query = String.format("from %s where %s = ? ", entityClass.getName(), uniqueField);
    List<?> list = hibernateTemplate.find(query, property);

    return list != null && list.size() > 0;
}

public SessionFactory getSessionFactory() {
    return hibernateTemplate != null ? hibernateTemplate.getSessionFactory() : null;
}

@Autowired
public void setSessionFactory(SessionFactory sessionFactory) {
    this.hibernateTemplate = new HibernateTemplate(sessionFactory);
}
}

Thank you for your help.

/D

Update
After changing the code I am getting this error:

org.hibernate.HibernateException: No Hibernate Session bound to thread, and configuration does not allow creation of non-transactional one here

So I’m thinking that maybe I haven’t injected the SessionFactory properly?

UniqueIdValidator.java:

package testapp.mis.validator;
import java.io.Serializable;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

import org.hibernate.Criteria;
import org.hibernate.SessionFactory;
import org.hibernate.criterion.Restrictions;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.transaction.annotation.Transactional; // Added in update 2


public class UniqueIdValidator implements ConstraintValidator<Unique, Serializable> {

@Autowired(required=true)
private SessionFactory sessionFactory;

private Class<?> entityClass;
private String uniqueField;

public void initialize(Unique unique) {
    entityClass = unique.entity();
    uniqueField = unique.property();
}

    @Transactional //Added in update 2 and validation works after that
public boolean isValid(Serializable property, ConstraintValidatorContext cvContext) {
    Criteria crit = sessionFactory.getCurrentSession().createCriteria(entityClass);
    crit.add(Restrictions.eq(uniqueField, property));
    return crit.list().isEmpty();
}

Update 2
I got it working by adding @Transactional in the code.

Answer 1

That uses plain HQL, you can achieve something simpler by using the Criteria API, something like:

public boolean isValid(Serializable property, ConstraintValidatorContext cvContext) {
    Criteria crit = sessionFactory.getCurrentSession().createCriteria(entityClass);
    crit.add(Restrictions.eq(uniqueField, property));
    return crit.list().isEmpty();
}

That should check for uniqueness.

Instead of injecting the hibernate template, just inject the SessionFactory which you also should have configured in your spring context.

Hope you find it useful!