Unique validation for Play!Framework

Unique.java

package utils.validation;

import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import java.lang.annotation.ElementType;
import java.lang.annotation.RetentionPolicy;

import net.sf.oval.configuration.annotation.Constraint;

@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.FIELD, ElementType.PARAMETER })
@Constraint(checkWith = UniqueCheck.class)
public @interface Unique {

  String message() default UniqueCheck.message;

}

UniqueCheck.java

package utils.validation;

import java.lang.reflect.Field;

import play.db.jpa.JPQL;
import play.db.jpa.Model;

import net.sf.oval.Validator;
import net.sf.oval.context.OValContext;
import net.sf.oval.context.FieldContext;
import net.sf.oval.exception.OValException;
import net.sf.oval.configuration.annotation.AbstractAnnotationCheck;

public class UniqueCheck extends AbstractAnnotationCheck<Unique> {

  final static String message = "validation.unique";

  @Override
  public boolean isSatisfied(Object validatedObject, Object value,
      OValContext context, Validator validator) throws OValException {

    if (value == null) {
      return true;
    }

    Model validatedModel = (Model) validatedObject;

    Field field = field(context);

    String fieldName  = field.getName();
    Object fieldValue = fieldValue(field, validatedObject);
    
    Object[] params = { fieldValue };

    Model model = JPQL.instance.find(validatedModel.getClass().getName(), fieldName + " = ?", params).first();
    if (model == null) {
      return true;
    }

    if (model.id.equals(validatedModel.id)) { // same object
      return true;
    }

    return false;
  }

  private Object fieldValue(Field field, Object validatedObject) {
    try {
      return field.get(validatedObject);
    } catch (Exception ex) {
      throw new RuntimeException(ex);
    }
  }

  private Field field(OValContext context) {
    return ((FieldContext) context).getField();
  }
}