Add a Custom message for the Unique Constraints in hibernate

Question

@Entity @Table(name=\"users\",uniqueConstraints = {@UniqueConstraint(columnNames = {\"email\"})})
public class User implements Serializable {
    @Column(unique = tr         


        

Answer 1

User defined annotation "@Unique" in the model User.java

@Column(unique = true,name = "email")
@Unique(message = "{Unique.email}")
private String email;

message.properties

Unique.email = Email id already exists

Unique.java

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import javax.validation.Constraint;
import javax.validation.Payload;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

@Documented
@Target({ElementType.METHOD, ElementType.FIELD})
@Constraint(validatedBy = UserUniqueValidator.class)
@Retention(RUNTIME)
public @interface Unique {
    String message();
    Class[] groups() default { };
    Class[] payload() default { };
}

UserUniqueValidator.java

import com.User;
import com.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

public class UserUniqueValidator implements ConstraintValidator {

    @Autowired
    private UserService userService;

    @Override
    public void initialize(Unique unique) {
        unique.message();
    }

    @Override
    public boolean isValid(String email, ConstraintValidatorContext context) {
        if (userService != null && userService.existsByEmail(email,User.class)) {
            return false;
        }
        return true;
    }
}

UserService.java

public interface UserService {
    public boolean existsByEmail(String email,Class clazz);
}

UserServiceImpl.java

import com.UserRepository;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Service
@Transactional
public class UserServiceImpl extends UserRepository implements UserService  {

    @Override
    public boolean existsByEmail(String email, Class clazz) {
        return super.existsByEmail(email,clazz);
    } 

}

UserRepository.java

public class UserRepository {
  public boolean existsByEmail(String email, Class className) {
      Criteria criteria = getSession().createCriteria(className,"userEmail");
      criteria.add(Restrictions.eq("email",email));
      if(criteria.list().size() == 0){
            return false;
      }
      return true;
  }
}