Complementing Visualforce - Girafa Thumbnail Service

Kyle
Roche

There are so many technologies out there to complement your Salesforce.com projects. In a previous posting I showed you how to leverage Google's Geocoding API from within your APEX classes. In this example, let's take a look at something more useful in the UI Layer.

It's pretty typical in projects with heavy Visualforce development to create a custom search form. Recently, I was working on a project where we created a custom search form for the Account object. Instead of showing the Account's logo image, we were thinking it would be a cool enhancement to display a thumbnail to the Account's website. You could use services like Amazon's Alexa Site Thumbnail Service (as shown in the APEX Language Reference). However, most of these aren't free. After some Googling, I stumbled on the Girafa Thumbnail Service, which offers a free service to those who use less than 2000 images requests per day (200 request per day at the time of this writing. Please check girafa for updated daily limits).

Let's get started. Create a Visualforce page called GirafaThumbnail and a controller called GirafaThumbnailController. In your controller add the following APEX Property.

public string GirafaUrl
{
get
{
if (GirafaUrl == null)
{
string algorithmName = 'MD5';
string signatureKey = 'your signature key here';
string clientId = 'your client id here';
string siteUrl = 'http://www.appirio.com/';
string inputString = signatureKey + siteUrl;
Blob myDigest = Crypto.generateDigest(algorithmName, Blob.valueOf(inputString));
string myDigestString = EncodingUtil.ConvertToHex(myDigest);
integer myStartingPosition = myDigestString.length() - 16;
integer myEndingPosition = myDigestString.length();
string mySubString = myDigestString.substring(myStartingPosition, myEndingPosition);
string myUrl = 'http://scst.srv.girafa.com/srv/i?i=' + clientId + '&s=' + mySubString + '&r=' + siteUrl;
return myUrl;
}
return GirafaUrl;
}
set;
}

Let's break this down by first understanding how girafa thumbnail service works. There are a few basic steps to generating the URL for your thumbnail. Girafa's thumbnail images are embedded using the <img> tag. The call is formatted as follows:

http://scst.srv.girafa.com/srv/i?i=<client ID>&s=<signature>&r=<site URL>

client ID is your Girafa Client ID. It is supplied when you register your account. The site URL is the URL of the website for which you would like to generate a Thumbnail. In our example http://www.appirio.com

The signature authenticates your request and is generates using the following steps:

1) Concatenate your secrete key (chosen when you create your account) and the Site URL

2) Calculate the MD5 Checksum of the concatenated string.

3) The signature is the 16 least significant hexadecimal digits of the MD5 checksum.

In our method we set the variables we'll need to generate the Image call then we use the Crypto class' generateDigest() method to calculate the MD5 checksum of our concatenated string. Some basic string manipulation returns the 16 character substring and we put our URL together to return to our caller.

In your Visualforce page add an image tag to see the results. Bind the src attribute of the <img> to our APEX Property. <img src="{!GirafaUrl}"></img>. You should see something along the lines of the following illustration.