Roll your own Ajax-Based Captcha in Grails

Recently, I was asked to come up with a better solution to our captcha needs. We have been using ReCaptcha, which is great but difficult to read at times, and has caused frustrated customers and lost sales. I found a great solution at http://www.jkdesign.org/captcha which displays a number of graphics and let's the user choose the right one to prove they are human. Here is a screenshot of my implementation:

To make this work within Grails, I had to make several tweaks. The following files are required:

• JQuery 1.2+ (I am using version - 1.4.2)
• JQuery UI (I am using version - 1.8.2)
• jquery.simpleCaptcha-0.2.js
• Captcha Images placed in images/captchaImages
• BCrypt.java by Damien Miller
• CaptchaController.groovy (below)

Create a new controller called Captcha. This can really be named anything, but if you do rename it, it will have to be updated in the jquery.simpleCaptcha-0.2.js file or passed in as an option via the javascript.

What this controller does is return a JSON object with the data needed to generate the captcha. The JSON appears like so:

Now we just need to implement this in our GSP file and controller. Suppose we have a page like shown above with a pickup code and the last 4 digits of the persons phone number. With adding our captcha div and required javascript, our GSP would look like this:

Finally, we need to perform the validation on the controller side. The modified authentication action would look like the following:

So there ya go. It's actually pretty easy and customers seem to like choosing an image much more than typing a word that is difficult to read.

Uploading Files in Grails

Here's the slides from a presentation I did at the UGGUG in May 2010. I found that I needed to use it again today so I posted it.

Upload files with grails

View more presentations from Eric Berry.

Here is the source code for the uploader service I created:

A tip that you may enjoy is the way I implemented this uploader into a real world application. I wanted to be able to upload files into a folder within the web-app folder for development, but in production, I wanted to put it in a folder that is served via Tomcat directly. So on our production server, I created a folder at /opt/assets and created a symbolic link in the $TOMCAT_ROOT/webapps/assets to point to it. I modified the service as follows:

I then create a folder in my web-app folder named 'assets', being sure to add it to my ignore list for the repository. So once I upload the file, it will save to the correct location.

Now to view the image, all I have to do is the following:

This now will work in both DEVELOPMENT and PRODUCTION enviroments.

http://github.com/cavneb/FileUploader

Using Tag Lib within Controllers and Services

So let's say you want to utilize the standard grails tag lib of formatNumber within your domain class, controller or service. How would you go about doing it? With the help of a blog post by Lucas Teixeira, I was able to get it working without an issue. Here is the code:

It's also simple to utilize your own tag libs as well. Here's a tag lib that I created to help with XML formatting:

So to call this tag lib in the domain class, controller or service, I just need to do the following:

Just make sure that you include the 'def grailsApplication' in the beginning.

Got Groovy?

One of the things I really love about the Groovy language is how quickly you can accomplish things. There has been a lot of thought put into making the language easier to use and it really shows.

All though I highly recommend reading through the GDK to really understand all the great stuff that Groovy has to offer, sometimes you just need to know how to do something quickly.

I stumbled upon a nicely organized Groovy version of the PLEAC (programming language examples alike cookbook). It's chalk full of examples on how to quickly accomplish common tasks and is a great demonstration of the power of Groovy.