Alternative to Using Valang Custom Functions

Valang provides a rich set of validation tools and is pretty simple. However in some cases you want more. The most obvious case that we encounter is validating if a date is in future or past wrt the current time on server. I know we can parse and input date to a date object readily using initBinder function of a SimpleFormController. But to compare it with the current date using pure varlang is something I could not find.

Luckily valang has an ability to use custom function. However I found it cumbersome to make one separate class for each function I may need. It would make more sense to allow users to group functions in one class to build a custom library of functions. Not to mention I could not find a proper working example of a custom function. So till I get my hands on one and this implementation improves, I have a simple work around.

Step 1: Define valang validations in the config file

<bean id="webMessageFormValidator" 
class="myPackage.validators.FormBeanValidator">
   <property name="valang">
     <value>
     <![CDATA[
       {to:? IS NOT BLANK:'Please enter email addresses 
          for recepients.'}
       {subject:? IS NOT BLANK:'Mail can not be blank.'}          
       {from:(length(?)> 0):'Please specify at least one 
            address.'}
     ]]>
     </value>
   </property>
</bean>

Step 2: Define the validator as follows

package mypackage.validators;

import org.springframework.validation.Errors;
import org.springmodules.validation.valang.ValangValidator;
import mypackage.FormBean;


public class FormBeanValidator extends ValangValidator {

    public void validate(Object object, Errors errors) {

        FormBean form = (FormBean) object;

        //perform all validations and raise error flag
        //if you find an error
        if(isFutureTime(form.myDate()){
            errors.rejectValue("myDate", "error.futureDate"
            ,"Time cannot be in the future.");
        }
       
        //dont forget call to super so as the validations 
        //defined in XML take place
        super.validate(object, errors);
    }


    private boolean isFutureTime(Date formDate, 
                          int hours, int minutes){
        //check if time is in future
        return false;
  }