String Validations using Custom provider

String Validations using Custom provider

Hello,

I need to validate String valuholders like 

1) Restrict Size to 5

2) Check for numeric, letters etc.

I have tried extending the NdStringProvider and then overriding the checkInstantiationValue method which throws an exception.

While using this, the exception is thrown only on compiling/refreshing the code.

Is there any way it can work as soon as I enter the incorrect value, like it works for the Integer provider when a non numeric is entered, which is internally handled by Blaze..?

Or is there any other method of doing this..?

Any help will be appreciated!

Thanks