Last week we ran up a JRuby contacts tracking app which we deployed on AWS. It’s small but beautifully-formed – insert your own joke now – and is a lot better than our having to exchange emails with contacts and leads.

Despite that, yesterday I got fed up of copying contacts from LinkedIn to the app so I thought I’d add a way the user can browse and add their LinkedIn contacts. This was straightforward enough to do in a day, but also had a few gotchas along the way so after a quick bit of background I thought I’d share those.

LinkedIn provide both a JS and a REST API to their
services and split the API in to three primary domains:

• Profile API – to get information about people (e.g. name, role, company, etc.)
• Connections – provides a list of connections for a user
• People Search API – which mimics the search capabilities when you log in to LinkedIn

There are a couple of other APIs around Invitations and Sharing updates etc but those were less of interest to what we were trying to achieve.

Our goal was pretty simple – to save data entry by accessing our connections from LinkedIn and copying their name, role, company, and LinkedIn profile to our contacts application.

This broke down in to 5 technical tasks:

1. Register our contacts application with LinkedIn (needed for the authentication
   step)
2. Authenticate using OAuth and the tokens provided from registration
3. Retrieve connections
4. Pull profile information from each connection
5. Save contact information in to the contacts database

LinkedIn uses OAuth to authenticate and authorize and having had fun in the past with OAuth and Google I was glad this time to see that Wynn’s API not only wrapped OAuth but also had some examples that worked
out of the box.

I’m not going to replicate the code here so I recommend people take a look.

With authentication, the only issue I had was with the OAuth gem under JRuby. It was throwing an exception “Wrong # of arguments (3 for 2)” in the digest.rb class. All that it needed was a different Digest object to be instantiated. I put the following code in to a module called digest.rb and all was well:

require 'oauth/signature/base'
require 'digest/hmac'
require 'openssl'
#
# Hack/fix to allow oauth to be used with JRuby / Tomcat.
# The digest class doesn't work so use the OpenSSL digest class instead
#
#
module OAuth::Signature::HMAC
  class Base < OAuth::Signature::Base
    private
      def digest
        self.class.digest_class Object.module_eval("::Digest::#{self.class.digest_klass}")
        digest  = OpenSSL::Digest::Digest.new('sha1')
        OpenSSL::HMAC.digest(digest, secret, signature_base_string)
      end
   end
end

Once authenticated then it’s just a case of using the methods in the gem’s
Client class to fetch back the objects. Not all of the API is supported but there was enough for what we needed to do. Again, the detail is in the gem source and examples, and the only more “complex” thing that we did was to take the “headline” field (e.g. my headline is Co-Founder at True North) and split that in to a role and position.

# most are --role-- at --company-- but will not fit all
posn_company = lic.headline.split(" at ")
posn=posn_company[0]
company=posn_company[1]||""

Not everybody’s is in this format but enough are to make it not worth going any more complex.

Finally it was a case of deploying on to our running version of contacts on AWS. We used a modified Ubuntu/Tomcat/MySQL bitnami stack again as it’s been good to us before and is pretty straightforward to set up.

This is where the final gotcha
got me. The version of Ubuntu didn’t have some of the XML libraries needed and I ended up with “Could not open library xml2 libxml2.so”. This was just a case of installing those libraries on the machine.

Again, the joy of AWS and the bitnami AMI we could just run
sudo apt-get install libxml2 libxml2-dev libxslt1-dev. I made a us a new AWS AMI with the patch in (so I don’t have to remember again).

For us that was it. The code itself was quick to do – some of the issues took time but by the end of the day we were all happily importing from LinkedIn.

Ping me on http://twitter.com/truenorth_sid if you want to know more or are interested in a cloud-based contacts tracker with LinkedIn integration!

Finally, in order to protect the innocent, the screenshot above is test data generated by Benjamin Curtis’ Faker gem rather than our real contacts!