Jani Hartikainen has written up a new post for his blog looking at how to combine multiple password validation methods inside of a single application.

If your application is well thought out, you would not want to save any data that isn’t valid. So what do you do, when you need different validation schemes, say for passwords, depending on some special case? [...] There is a better approach: Using a “policy” - Policies can be used for other things than this too, but let’s look at how to use a policy for managing password validation.

He sets up an example scenario where the user sets an invalid and valid password and shows how policies for password validation (regular expression matches and other validation techniques) can provide a simple way to ensure the user has entered the right information.