Integrating Regula with Spring 3.0.x MVC

A little less than a year ago, I released Regula, an annotation-based form-validation written in Javascript. The source and documentation are available on GitHub. I started working on the integration on and off throughout most of last year. At the end of the year, I had a pretty good integration going, where you could annotate fields with Hibernate Validator annotations, and the corresponding Regula validation-code would be generated on the client side. Of course, I wasn't done yet because what I had was simply a demo project and I had to figure out a good way to distribute the whole thing; I was able to finish up the packaging and distribution today. With minimal setup, you should be able to get started with Regula and Spring. You don't need to go through this post to figure out how to use the integration. This post is mostly about how I accomplished the integration (I don't go into all the details; just the important bits). As far as actually using it, I will make a blog post about it later.

The source for the integration is also hosted on GitHub. My approach towards translating validation constraints from the server-side to the client-side was two-fold: gather validation constraints from the object and represent it in a canonical form. Using the canonical form, generate Javascript code that uses Regula for validation. To do this, I created a service that examines a domain object and gathers all information regarding its properties and validation constraints. The service returns this information in a canonical form, that I then inserted into the model. On the client-side, I had a tag that used the canonical form and outputted Javascript that uses the Regula framework. Initially, I was calling the service explicitly from an action in the controller. Later, in an effort to make the integration less-invasive and more seamless, I used an aspect-oriented approach with interceptors. In fact, that's where I'd like to start.

I created an annotation called @ValidateClientSide that marks a domain object as requiring client-side validation. Then, I created an interceptor called ClientSideValidationInterceptor that will call the validation service and gather validation information: