Rough Book

random musings of just another computer nerd

Tag: annotation-based form-validation

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.
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Regula: An annotation-based form-validator written in Javascript

Regula is an annotation-based form-validation framework written in Javascript. There already exist a few frameworks that address form-validation in Javascript, but I have found them to be somewhat lacking. I have thought about writing one of my own for some time, but I honestly had no idea what form it would or should take. I knew that I wanted to make one that was easy to use, flexible, and easily extensible (custom validation rules). I finally got an idea as to the form my framework should take, when I was looking at Hibernate bean-validation. I like the fact that you can set constraints by using annotations like @NotNull or @NotEmpty. That way, when you look at the bean, you are immediately aware of the constraints attached to it. I wanted to do something similar in HTML.
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